BOSCH Gasoline-engine management Basics components.pdf

Order Number 1 987 722 036 AA/PDI-02.01-En The Bosch Yellow Jackets Edition 2001 Technical Instruction Gasoline-engine management 2001 Gasoline-engine The Bosch Yellow Jackets management Basics and components Æ The Program Order Number ISBN Gasoline-engine management: Basics and components Automotive electrics/Automotive electronics Batteries 1 987 722 153 3-934584-21-7 Automotive Technology Alternators 1 987 722 156 3-934584-22-5 Starting Systems 1 987 722 170 3-934584-23-3 Lighting Technology 1 987 722 176 3-934584-24-1 Electrical Symbols and Circuit Diagrams 1 987 722 169 3-934584-20-9 Safety, Comfort and Convenience Systems 1 987 722 150 3-934584-25-X Diesel-Engine Management Diesel Fuel-Injection: an Overview 1 987 722 104 3-934584-35-7 Electronic Diesel Control EDC 1 987 722 135 3-934584-47-0 Diesel Accumulator Fuel-Injection System Common Rail CR 1 987 722 175 3-934584-40-3 Diesel Fuel-Injection Systems • EGAS electronic throttle control Unit Injector System/Unit Pump System 1 987 722 179 3-934584-41-1 • Gasoline direct injection Radial-Piston Distributor Fuel-Injection Pumps Type VR 1 987 722 174 3-934584-39-X • NOx accumulator-type catalytic converter Diesel Distributor-Type Fuel-Injection Pumps VE 1 987 722 164 3-934584-38-1 Diesel In-Line Fuel-Injection Pumps PE 1 987 722 162 3-934584-36-5 Technical Instruction Governors for Diesel In-Line Fuel-Injection Pumps 1 987 722 163 3-934584-37-3 Gasoline-Engine Management Emission Control (for Gasoline Engines) 1 987 722 102 3-934584-26-8 Gasoline Fuel-Injection System K-Jetronic 1 987 722 159 3-934584-27-6 Gasoline Fuel-Injection System KE-Jetronic 1 987 722 101 3-934584-28-4 Gasoline Fuel-Injection System L-Jetronic 1 987 722 160 3-934584-29-2 Gasoline Fuel-Injection System Mono-Jetronic 1 987 722 105 3-934584-30-6 Spark Plugs 1 987 722 155 3-934584-32-2 Ignition 1 987 722 154 3-934584-31-4 M-Motronic Engine Management 1 987 722 161 3-934584-33-0 ME-Motronic Engine Management 1 987 722 178 3-934584-34-9 Gasoline-Engine Management: Basics and Components 1 987 722 136 3-934584-48-9 Driving and Road-Safety Systems Conventional Braking Systems 1 987 722 157 3-934584-42-X Brake Systems for Passenger Cars 1 987 722 103 3-934584-43-8 ESP Electronic Stability Program 1 987 722 177 3-934584-44-6 Compressed-Air Systems for Commercial Vehicles (1): Systems and Schematic Diagrams 1 987 722 165 3-934584-45-4 Compressed-Air Systems for Commercial Vehicles (2): Equipment 1 987 722 166 3-934584-46-2 Robert Bosch GmbH
Imprint Published by: Reproduction, duplication, and translation of this © Robert Bosch GmbH, 2001 publication, including excerpts therefrom, is only Postfach 300220, to ensue with our previous written consent and D-70442 Stuttgart. with particulars of source. Illustrations, descrip- Automotive Aftermarket Business Sector, tions, schematic diagrams and other data only Department AA/PDI2 serve for explanatory purposes and for presenta- Product-marketing, software products, tion of the text. They cannot be used as the technical publications. basis for design, installation, and scope of deliv- ery. Robert Bosch GmbH undertakes no liability Editor-in-Chief: for conformity of the contents with national or Dipl.-Ing. (FH) Horst Bauer local regulations. All rights reserved. Editors: We reserve the right to make changes. Dipl.-Ing. Karl-Heinz Dietsche, Dipl.-Ing. (BA) Jürgen Crepin. Printed in Germany. Imprimé en Allemagne. Authors: Dipl.-Ing. Michael Oder 1st Edition, September 2001. (Basics, gasoline-engine management, English translation of the German edition dated: gasoline direct injection), February 2001. Dipl.-Ing. Georg Mallebrein (Systems for cylinder-charge control, variable valve timing), Dipl.-Ing. Oliver Schlesinger (Exhaust-gas recirculation), Dipl.-Ing. Michael Bäuerle (Supercharging), Dipl.-Ing. (FH) Klaus Joos (Fuel supply, manifold injection), Dipl.-Ing. Albert Gerhard (Electric fuel pumps, pressure regulators, pressure dampers), Dipl.-Betriebsw. Michael Ziegler (Fuel filters), Dipl.-Ing. (FH) Eckhard Bodenhausen (Fuel rail), Dr.-Ing. Dieter Lederer (Evaporative-emissions control system), Dipl.-Ing. (FH) Annette Wittke (Injectors), Dipl.-Ing. (FH) Bernd Kudicke (Types of fuel injection), Dipl.-Ing. Walter Gollin (Ignition), Dipl.-Ing. Eberhard Schnaibel (Emissions control), in cooperation with the responsible departments of Robert Bosch GmbH. Translation: Peter Girling. Unless otherwise stated, the above are all employees of Robert Bosch GmbH, Stuttgart. Robert Bosch GmbH Gasoline-engine management Basics and components Bosch Robert Bosch GmbH
Contents 4 Basics of the gasoline (SI) 48 Manifold fuel injection engine 49 Operating concept 4 Operating concept 50 Electromagnetic fuel injectors 7 Torque and output power 52 Types of fuel injection 8 Engine efficiency 54 Gasoline direct injection 10 Gasoline-engine management 55 Operating concept 10 Technical requirements 56 Rail, high-pressure pump 12 Cylinder-charge control 58 Pressure-control valve 15 A/F-mixture formation 59 Rail-pressure sensors 18 Ignition 60 High-pressure injector 62 Combustion process 20 Systems for cylinder-charge 63 A/F-mixture formation control 64 Operating modes 20 Air-charge control 22 Variable valve timing 66 Ignition: An overview 25 Exhaust-gas recirculation 66 Survey (EGR) 66 Ignition systems development 26 Dynamic supercharging 29 Mechanical supercharging 68 Coil ignition 30 Exhaust-gas turbocharging 68 Ignition driver stage 33 Intercooling 69 Ignition coil 70 High-voltage distribution 34 Gasoline fuel injection: An 71 Spark plugs overview 72 Electrical connection and inter- 34 External A/F-mixture formation ference-suppressor devices 35 Internal A/F-mixture formation 73 Ignition voltage, ignition energy 75 Ignition point 36 Fuel supply 37 Fuel supply for manifold 76 Catalytic emissions control injection 76 Oxidation-type catalytic converter 39 Low-pressure circuit for 77 Three-way catalytic converter gasoline direct injection 80 NOx accumulator-type catalytic 41 Evaporative-emissions control converter system 82 Lambda control loop 42 Electric fuel pump 84 Catalytic-converter heating 44 Fuel filter 45 Rail, fuel-pressure regulator, 85 Index of technical terms fuel-pressure damper, fuel tank, 85 Technical terms fuel lines 87 Abbreviations which nevertheless must still satisfy demands for high performance. This Yellow Jacket technical instruction manual deals with the technical concepts em- ployed in complying with the demands made upon a modern-day engine. This man- ual is at present in the planning stage. and the introduction of the 3-way catalytic converter in the middle of the eighties was a real milestone in this respect. and direct-injection gasoline engines promise fuel savings of up to 20%. Just lately though. Another Yellow Jacket manual explains the interplay between these concepts and a modern closed and open-loop control system in the form of the Motronic. and explains their operation. The increasingly stringent exhaust-gas legislation initially caused the main focus of concentration to be directed at reducing the toxic content of the exhaust gas. necessitates immense efforts to de- velop innovative engine concepts. the demand for more economical vehicles has come to the fore- front. Robert Bosch GmbH The call for environmentally compatible and economical vehicles. . the majority of the internal-combus- and externally supplied ignition. sion volume Vc). stems from this a direct-injection engine on the other hand. with manifold volume of the combustion chamber (7) so fuel-injection the A/F mixture is formed in that fresh air (gasoline direct injection) or the intake manifold. haust-and-refill cycle. fresh A/F mixture (manifold injection) is drawn into the combustion chamber past Even more advantages resulted from the de. velopment of gasoline direct injection. 1. or better ber at the end of the induction stroke. of fresh A/F mixture and the forcing out of the burnt exhaust gases. which permits extremely precise metering of 1st stroke: Induction the fuel. was the result of the legislation gov. Referred to top dead center (TDC). in particular with regard to fuel economy and The combustion chamber reaches maxi- increases in power output. At top dead center (TDC) the combustion- shaft. the chemical energy in the fuel into kinetic energy. and in the process control the supply the cylinder by the downgoing piston. ter (BDC). the carburetor was respon. The has already entered the combustion cham- name reciprocating-piston engine. fuel is first injected towards the end of the iprocating movement into a crankshaft (11) compression stroke. It burns an tion engines used as vehicle power plants are air/fuel mixture and in the process converts of the four-stroke type. the pis- erning exhaust-gas emission limits. 2nd stroke: Compression The gas-exchange valves are closed. With still reciprocating engine. In doing so it reduces the combustion-chamber The combustion of the A/F mixture causes volume and compresses the A/F mixture. and the Operating concept piston is moving upwards in the cylinder. rotational movement which is maintained by a flywheel (11) at the end of the crank. 1)Named after Nikolaus Otto (1832-1891) who presented the first gas engine with compression using the 4-stroke principle at the Paris World Fair in 1878. manifold-injection engines the A/F mixture rocating movement in the cylinder (9). . Crankshaft speed is also referred to as chamber volume is at minimum (compres- engine speed or engine rpm. close the cylinder’s intake and exhaust pas- take manifold which was then drawn into sages. On the piston (Fig. Robert Bosch GmbH 4 Basics of the gasoline (SI) engine Operating concept Basics of the gasoline (SI) engine The gasoline or spark-ignition (SI) internal. the opened intake valve (5). der at exactly the right instant in time. principle of functioning. Direct injection mum volume (Vh+Vc) at bottom dead cen- injects the fuel directly into the engine cylin. Similar ton is moving downwards and increases the to the carburetor process. depending upon the operating mode. The breakthrough of gasoline fuel-injection. Four-stroke principle combustion engine uses the Otto cycle1) Today. Pos. These valves open and sible for providing an A/F mixture in the in. the The conrod (10) converts the piston’s rec. The four-stroke principle employs gas-ex- change valves (5 and 6) to control the ex- For many years. 8) to perform a recip. the spark plug (2) initiates the com. of the crankshaft. On tion point (ignition angle). sure in the cylinder to such an extent that Gas flow and gas-column vibration effects the piston is forced downward. This is the rea- The exhaust valve (6) opens shortly before son for the valve opening and closing times bottom dead center (BDC). overlapping in a given crankshaft angular- haust) gases are under high pressure and position range. 1 Complete working cycle of the 4-stroke spark-ignition (SI) gasoline engine (example shows a manifold-injection Figure 1 engine with separate intake and exhaust camshafts) a Induction stroke b Compression stroke c Power (combustion) 1 stroke 2 a b c d d Exhaust stroke 3 1 Exhaust camshaft 4 2 Spark plug 3 Intake camshaft 5 OT Vc 4 Injector 5 Intake valve 6 6 Exhaust valve 7 Vh s 7 Combustion chamber UT 8 Piston 8 9 Cylinder 9 10 Conrod 11 Crankshaft 10 α M Torque æ UMM0011-1E 11 α Crankshaft angle M s Piston stroke Vh Piston displacement Vc Compression volume . gear pair). leave the cylinder through the exhaust valve. The hot (ex. The camshaft is driven from the crank- The remaining exhaust gas is forced out by shaft through a toothed belt (or a chain or the upwards-moving piston. On 4-stroke engines. tion. haust camshafts (3 and 1 respectively). The piston has already passed its TDC change valves. are applied to improve the filling of the combustion chamber with A/F mixture and 4th stroke: Exhaust to remove the exhaust gases. point before the mixture has combusted The valve timing defines the opening and completely. Robert Bosch GmbH Basics of the gasoline (SI) engine Operating concept 5 3rd stroke: Power (or combustion) Valve timing Before the piston reaches top dead center The gas-exchange valves are opened and (TDC). This form of ig. a lever mecha- nition is known as externally supplied igni. In other words. nism transfers the cam lift to the gas-ex- tion. a complete working cycle takes two rotations of the A new operating cycle starts again with the crankshaft. closed by the cams on the intake and ex- bustion of the A/F mixture at a given igni. the camshaft induction stroke after every two revolutions only turns at half crankshaft speed. closing times of the gas-exchange valves. engines with only 1 camshaft. The gas-exchange valves remain closed Since it is referred to the crankshaft posi- and the combustion heat increases the pres. timing is given in “degrees crankshaft”. The principle in which an ignitable A/F- æ UMM0557Y a b mixture cloud only fills part of the combus- tion chamber is referred to as stratified charge (Fig. optimum (14. the compression (λ > 1. Air/fuel (A/F) ratio Stratified-charge In order for the A/F mixture to burn At the ignition point. Referred to the combustion chamber as a whole.6) the A/F mixture reaches the ratio ε = 7. λ = 1 indicates that the sive effect upon engine is running with a stoichiometric (in other words. theoretically optimum) A/F
The torque generated by the engine. 2b). 2a). On manifold-injection engines. or with a non-com- chamber bustible gas containing no gasoline at all.. and the leads to λ values of less than 1. mixture is leaned off (addition of more air) λ is more than 1..7:1). the A/F pression pressure and the resulting high mixture is distributed homogeneously in the temperatures in the combustion chamber combustion chamber and has the same λ would for this reason cause automatic. This in engines which operate in certain ranges with turn causes knock which can lead to engine excess air.24) which are common Distribution of the A/F mixture in the for the diesel engine cannot be used for the combustion chamber gasoline engine. Robert Bosch GmbH 6 Basics of the gasoline (SI) engine Operating concept Compression This is the so-called stoichiometric The compression ratio ε = (Vh+Vc)/Vc is ratio (14.7:1).
The engine’s power output. and the high com. been chosen to indicate how far the actual A/F mixture deviates from the theoretical The engine’s compression ratio has a deci. there is an ignitable completely 14. Lean-burn controlled ignition of the gasoline.. This form of lean-burn operation leads to fuel-consumption savings. In effect. un.13.7 kg air are needed for 1 kg A/F-mixture cloud (with λ = 1) in the vicin- fuel. ity of the spark plug. Above a given limit With the gasoline engine. the A/F mixture is very lean (up to λ ≈ 10). Homogeneous distribution ited antiknock qualities. Enriching the A/F mixture with more fuel
The engine’s fuel consumption. the stratified-charge principle is only applicable with gasoline direct injec- tion. ratio. number throughout (Fig. injection or direct injection). calculated from the piston displacement Vh The excess-air factor (or air ratio) λ has and the compression volume Vc.. also run with homogeneous mix- damage. The compres- sion ratios (ε = 14. and if the A/F
Toxic emissions. depending upon engine type so-called lean-burn limit and cannot be and the fuel-injection principle (manifold ignited. The remainder of the combustion chamber is filled with either a 2 A/F mixture distribution in the combustion very lean A/F mixture. Gasoline has only very lim. The stratified charge is the direct result Figure 2 a Homogeneous A/F- of the fuel being injected directly into the mixture distribution combustion chamber only very shortly be- b Stratified charge fore the ignition point. . ture distribution. m 140 Mmax Torque M M 120 Figure 1 100 æ SMM0558E Mmax Maximum torque 1000 3000 5000 min-1 Pnenn Nominal power Engine rpm n nnom nnenn Nominal engine speed . torque is the product of force bocharging comply with this demand. Force and lever arm are nnom. The lever arm which is ef. adapt the engine to the requirements of lect the ignition angle so that the ignition of everyday driving. It is therefore necessary to se. speeds around 2000 min-1. combustion-chamber geome- try) determines the maximum possible kW torque M that it can generate. the conrod manifold-injection gasoline engine. 40 The engine’s power output P climbs along 20 with increasing torque M and engine speed n. since it is in this nal-combustion engine. 1 shows the typical torque and power- output curve. Robert Bosch GmbH Basics of the gasoline (SI) engine Torque and output power 7 Torque and output power Fig. The following applies: 1000 3000 5000 min-1 Engine rpm n nnom P = 2·π·n·M N. against engine rpm. engine speeds. at the engine’s nominal speed vertical to the force. Today. force with which the expanding A/F mixture Along with increasing engine speed. the Pnom 80 torque is adapted to the requirements of ac- tual driving by adjusting the quality and 60 Power P P quantity of the A/F mixture. the lever arm is The power and torque curves of the inter- vertical to the generated force. On the inter. rating Pnom. The engine’s design (for instance. These converts the piston’s reciprocal movement diagrams are often referred to in the test re- into crankshaft rotational movement. the lever arm is de. Engines with exhaust-gas tur- In general. so that the ef. Engine power increases along with engine fective for the torque is the lever component speed until. engine-speed range that fuel economy is at fined by the crankshaft throw. torque drops again. At higher into torque. torque forces the piston downwards is converted increases to its maximum Mmax. engine development is aimed at achieving In addition to the force. Essentially. it reaches a maximum with its nominal parallel to each other at TDC. At a crank- shaft angle of 90° after TDC. its highest. for a Via the cranks on the crankshaft. This enables the engine to gener- ate the maximum-possible torque. fective lever arm is in fact zero. the A/F mixture takes place in the crankshaft angle which is characterized by increasing lever arm. and the lever nal-combustion (IC) engine make it impera- arm and with it the torque is at a maximum tive that some form of gearbox is installed to in this setting. The ports published in automobile magazines. times lever arm. piston 1 Example of the power and torque curves of a manifold-injection gasoline engine displacement. the lever arm is the maximum torque already at low engine decisive quantity for torque. The pres. 1). of the added energy is lost. Fig. compressed without the addition of heat The energy needed for this process is in the (Boyle/Mariotte). The higher the compression. This means that the sure of the burnt gases drops whereby no compressed A/F mixture is at a lower tem- heat is released (Boyle/Mariotte). On an exhaust-gas turbocharged engine. During the formation of the (point 1 to point 2). The exhaust valve opens at gasoline direct injection. This means that an engine’s efficiency is less than 100% Measures for increasing thermal efficiency (Fig. In the case of working cycle. This area is an indi- plete working cycle of the 4-stroke IC en. The thermal efficiency rises along with in- portant links in the engine’s efficiency chain. take valve. curve B) differs in the fuel into mechanical work. ders the transfer of heat to the cylinder walls scribed by 1 – 4 – 5 would represent usable and therefore reduces the thermal losses. and the larger is the enclosed sure and volume conditions during a com. . the perature than is the case with a manifold-in- burnt mixture cools off again with the jection engine. Robert Bosch GmbH 8 Basics of the gasoline (SI) engine Engine efficiency Engine efficiency Real p-V diagram Since it is impossible during normal engine Thermal efficiency operation to maintain the basic conditions The internal-combustion does not convert for the ideal constant-volume cycle. the piston travels needed for fuel-droplet vaporization is taken towards BDC (point 4). energy. Thermal efficiency is one of the im. and some from the ideal p-V diagram. 2 (curve A) shows the compression and Manifold-injection engines inject the fuel power strokes of an ideal process as defined into the intake manifold onto the closed in- by the laws of Boyle/Mariotte and Gay-Lus. area in the p-V diagram. the higher the pres- Pressure-volume diagram (p-V diagram) sure in the cylinder at the end of the com- The p-V diagram is used to display the pres. cools off as a result. and the energy From TDC (point 3). pression phase. On direct-injec- 2 to point 3) while volume remains constant tion engines the fuel is injected into the (Gay-Lussac). and the A/F mixture is A/F mixture. When selecting the compression ratio. If it were jacket of gases which do not participate in possible for the gas to expand completely by the combustion process. Finally. combustion process. Part of this thermal shows the work gained during a complete energy is radiated and lost. Subsequently. the mixture form of heat and is taken from the air and burns accompanied by a pressure rise (point the intake-manifold walls. until the initial status (point 1) is reached again. the part above the line (1 bar) can to some extent be utilized (1 – 4 – 5
). charge A/F mixture cloud is surrounded by a sure. cation of the energy generated during the gine. creasing A/F-mixture compression. which is still under pres. and the combus. so that a higher compression volume remaining constant (Gay-Lusac) ratio can be chosen. combustion chamber. Thermal losses The heat generated during combustion heats The area inside the points 1 – 2 – 3 – 4 up the cylinder walls. The piston travels from BDC to TDC the cylinder. 2. from the air trapped in the cylinder which tion-chamber volume increases. the fine fuel droplets vaporise. the stratified- point 4 and the gas. escapes from the cylinder. the fuel’s antiknock qual- The ideal constant-volume cycle ities must be taken into account. where it is stored until drawn into sac. the ac- all the energy which is chemically available tual p-V diagram (Fig. the area de. This gas jacket hin- the time point 5 is reached. Efficiency is therefore less for a Frictional losses. due to the piston-ring friction at the tion. Since with a gasoline direct-injection engine the throttle valve is wide open at idle and part load. work is also involved in 2 forcing the remaining exhaust gases out of c the cylinder. For in- losses are reduced in stratified-charge opera. and exhaust-gas heat tive. the pumping losses (throttling losses) Cylinder pressure p A B are lower. The desired quantity of gas is controlled by the throttle-valve opening.. friction of the alternator drive. at λ > 1. and the residual heat of the exhaust gases. inefficient combustion. the en- gine draws in fresh gas during the 1st (in- duction) stroke. Due to the reduced flame-propaga. stance. a fact which has a negative effect upon 13% drive 10% the SI engine’s efficiency curve. p-V diagram fold which opposes engine operation (throttling losses). an Thermal losses in the cylinder. Losses at λ =1 The efficiency of the constant-volume cycle climbs along with increasing excess-air fac- tor (λ).1. A/F mixture with λ = 1 is absolutely impera. Robert Bosch GmbH Basics of the gasoline (SI) engine Engine efficiency 9 Further losses stem from the incomplete Frictional losses combustion of the fuel which has condensed The frictional losses are the total of all the onto the cylinder walls. 2 Sequence of the motive working process in the A vacuum is generated in the intake mani. efficiency is the highest in the range 15% λ = 1. Further thermal losses result from the cylinder walls.1 combustion is increasingly slug- Useful work. æ SMM0560E Thermodynamic losses during Pumping losses the ideal process (thermal efficiency) During the exhaust and refill cycle. auxiliary equipment homogeneous A/F-mixture formation with Pumping λ = 1 than it is for an A/F mixture featuring 45% losses excess air. In the 4th stroke.1. ZZ Figure 2 b 4 A Ideal constant- AÖ d 5 volume cycle 1 bar a 1 B Real p-V diagram Vc Vh 5 a Induction æ UMM0559E b Compression Volume V c Work (combustion) d Exhaust ZZ Ignition point AÖ Exhaust valve opens . Thanks to the friction between moving parts in the engine insulating effects of the gas jacket. When a 3-way catalytic converter Losses due to λ =1 is used for efficient emissions control. these itself and in its auxiliary equipment. gish. the bearing friction. In the final 10% 7% analysis. 1 Efficiency chain of an SI engine at λ = 1 tion velocity common to lean A/F mixtures. and the 3 torque is determined by the injected fuel mass.3.. ) Clutch losses 2 Engine Gearbox losses and transmission ratio 3 Clutch 4 Gearbox . the ignition lem. One of the major objectives in the develop- ment of the automotive engine is to generate SI-engine torque as high a power output as possible. pumping losses. Robert Bosch GmbH 10 Gasoline-engine management Technical requirements Gasoline-engine management In modern-day vehicles. The clutch torque is the in order to comply with the legal require. and the torque improving the engine’s efficiency. Particu. direct injection is the solution to this prob- chanical systems (for instance. A/C Auxiliary equipment compressor etc. that it develops high torque even at very low rotational speeds so that the driver has good acceleration at his disposal. less friction torque (frictional torque in the Fuel consumption can only be reduced by engine). system). which the engine operates the majority of the time. This makes Technical requirements torque the most important quantity in the management of the SI engine. This is the reason for it being so necessary to improve the engine’s efficiency at idle and part load 1 Torque at the drivetrain 1 1 2 3 4 Air mass (fresh-gas charge) Combustion Engine Clutch Drive Fuel mass torque torque torque torque Engine Clutch Gearbox Ignition angle (ignition point) – – – – – – Figure 1 1 Auxiliary equipment Exhaust and refill cycle. while at The power P delivered by an SI engine is de- the same time keeping fuel consumption fined by the available clutch torque M and and exhaust emissions down to a minimum the engine rpm n. Without electronics it would be impossible to comply with the increasingly A further demand made on the engine is severe emissions-control legislation. tal effect upon the normal engine’s favorable ing more and more important. needed to drive the auxiliary equipment larly in the idle and part-load ranges. they have superseded the purely me. in (Fig. 1). torque developed by the combustion process ments of emissions-control legislation. the conventional manifold-injec- tion SI engine is very inefficient. without at the same time having a detrimen- loop electronic control systems are becom. Slowly but efficiency in the upper load ranges. closed and open. and friction æ UMM0545-1E (alternator. Gasoline surely. In doing ing quantities: so. ing through the accelerator pedal. and cylinder-charge control (also known as
The moment in time when the ignition EGAS or ETC/Electronic Throttle Control). It is the objective of this form of jection point. it is determined by the follow. It is impossible to satisfy the driver determines the injected fuel quan- all these requirements without the use of tity. for instance when he/she wants to ac- The proportion of direct-injection SI en. engine. During lean-burn operation. and opens effect upon the generated torque. This is one of the most important assign- ments of the engine management. the appropriate fuel mass engine. spark initiates the combustion of the A/F the driver inputs a torque requirement mixture. Here. through the position of the accelerator pedal. Here. In order that all these stipulations are maintained in long-term operation. Basically speaking. lated in the “ignition” subsystem. power output. control to provide the torque demanded by and essentially stratified-charge operation the driver while at the same time complying can be classified as such. in the various subsystems for the air charge is calculated by the A/F- (ETC. the accelerator-pedal sensor gines will increase in the future. he/she defines the amount of fresh air drawn in by the engine. Subsystem: Ignition gine management continuously runs The crankshaft angle at which the ignition through a diagnosis program and indicates spark is to ignite the A/F mixture is calcu- to the driver when a fault has been detected. On conventional injection systems. other conditions with the severe demands regarding exhaust apply in the case of gasoline direct injection. fuel consumption. measures the pedal’s setting. A/F-mixture formation. and it also makes a valuable contribution to sim- plifying vehicle servicing in the workshop. and the “ETC” gines run with excess air at certain operating subsystem uses the sensor signal to define points (lean-burn operation) which means the correct cylinder air charge correspond- that there is air in the cylinder which has no ing to the driver’s torque input. the en. These en. on engine-management
The fuel mass which is available at the systems with electronic accelerator pedal for same moment. the dri- gines. To do so. . and from it the appro- quantities that influence torque are con.
The air mass which is available for com- bustion when the intake valves close. Here. accordingly. Engine-management assignments Subsystem: A/F-mixture formation One of the engine management’s jobs is to During homogeneous operation and at a de- set the torque that is to be generated by the fined A/F ratio λ. celerate. emissions. Robert Bosch GmbH Gasoline-engine management Technical requirements 11 The combustion torque is generated during Subsystem: Cylinder-charge control the power stroke. ignition) all mixture subsystem. the torque-requirement input from comfort and safety. In manifold-injection en. ver directly controls the throttle-valve open- day’s engines. and not the air mass drawn in by the electronics. priate duration of injection and the best in- trolled. which represent the majority of to. it is the electronically controlled throttle valve the fuel mass which has the most effect. It is defined as the ratio of the the torque and the engine load. 1 Cylinder charge in the gasoline engine The residual-gas share of the cylinder charge able valve-opening comprises that portion of the cylinder cross-section charge which has already taken part in the 6 Air-mass flow (ambi- combustion process. a manifold-injection engine. which enter the intake manifold through the haust-gas back EGR valve. standard conditions (p0 = 1013 hPa. The theoretical 3 Connection to the stream of the intake valve. The internal residual gas is that gas 8 Fresh A/F-mixture which remains in the cylinder’s upper clear- 1 charge (combustion. all the fuel has put power necessitate an increase in the section already been mixed with the fresh air up. 1). In this case. during valve overlap). bustion-chamber 8 pressure pB) External residual gas are the exhaust gases 9 10 Exhaust gas (ex. the air ferred to as the cylinder charge. ment. the torque (engine load) is a direct product Figure 1 T0 = 273 K). Almost al- 2 Canister-purge valve cylinder is comprised of the fresh air drawn ways. In principle. The gas mixture trapped in the combustion chamber when the intake valve closes is re. in and the fuel entrained with it (Fig. or that chamber pressure α 4 5 gas which is drawn out of the exhaust pas- pB) sage and back into the intake manifold when 9 Residual exhaust. On gine’s maximum torque and maximum out- opening cross. can be directed to the cylin- der via the evaporative-emissions control Components of the cylinder charge system (3). 4 Returned exhaust jected directly into the combustion chamber. the air mass tive-emissions con- trol system) The freshly introduced gas mixture in the can differ for the same torque. 1 Air and fuel vapor (from the evapora- Fresh gas During lean-burn operation. For homogeneous operation at λ ≤ 1. closed is the decisive quantity for the work The term “relative air charge rl” has been at the piston during the combustion stroke introduced in order to have a quantity and therefore for the engine’s output torque. 7) via the It is the job of the cylinder-charge control to throttle valve (13) and the intake valve (11). in the cylinder after the intake valve (11) has prised of the fresh gas and the residual gas. the fuel is in. on the other hand. the air charge corresponds to placement. ance volume following combustion. one differ- ent pressure pu) 7 Air-mass flow (mani. On direct-injec. During lean- actual air charge to the air charge under burn operation (stratified charge) though. gas Residual gas 5 EGR valve with vari. 2 3 entiates between internal and external resid- fold pressure ps) ual gas. coordinate all the systems that influence the Additional fresh gas. comprising fresh air proportion of gas in the cylinder. maximum possible charge. 11 12 gas charge (com- the intake and exhaust valves open together 6 13 7 10 (that is. and fuel vapor. pressure pA) æ UMM0544-3Y 11 Intake valve 12 Exhaust valve 13 Throttle valve α Throttle valve- angle . measures aimed at increasing the en- with variable valve. of the injected fuel mass. Robert Bosch GmbH 12 Gasoline-engine management Cylinder-charge control Cylinder-charge control The majority of the fresh air enters the cylinder with the air-mass flow (6. which is independent of the engine’s dis. This is com. maximum charge is defined by the displace- evaporative-emis- sions control system tion systems. the flow of air conditions apply as with manifold injection. some of function of throttle-valve opening. the throttle fect is a function of the throttle valve’s set. In the ideal case. it is not the air charge trapped in the cylinder which is decisive for the developed torque. This throttling ef. drawn in by the engine is throttled and the torque drops as a result. The selective use of a given share of residual gas can reduce the NOx emissions. In order to WOT). but rather the fuel injected into the combustion chamber. the same valve less than fully open. do not participate in the combustion process. the fresh-gas charge displaced by the inert gas must be compensated for by a larger throttle-valve opening. 1)Components in the combustion chamber which behave inertly. min. range. Controlling the fresh-gas charge Idle rpm Manifold injection The torque developed by a manifold-injec- tion engine is proportional to the fresh-gas Direct injection charge. . not all of the air mass entering the cylinder may Fig. The inert gas in the residual exhaust gas does not participate in the combustion dur- ing the next power stroke. Robert Bosch GmbH Gasoline-engine management Cylinder-charge control 13 Residual exhaust gas comprises inert gas1) 2 Throttle characteristic-curve map for an SI engine and. The engine’s torque is controlled via On direct-injection (DI) gasoline engines the throttle valve which regulates the flow of during homogeneous operation at λ ≤ 1 air drawn in by the engine. Maximum torque is developed with the tling losses with the throttle wide open (as it throttle wide open (Wide Open Throttle = is during full-load operation). during excess-air operation. unburnt – – – Intermediate throttle-valve settings air. in other words its opened cross-sec. that is. not lean-burn operation). To reduce the throttling losses. In other words. 2 shows the principal correlation be. This leads to a reduc- tion in pumping losses which in turn results æ UMM0543-2E Throttle fully closed in a reduction in fuel consumption. Fresh-gas charge In order to achieve the demanded torque. valve is also opened wide in the part-load ting. although it does have an influence on ignition and on the WOT combustion curve. In lean-burn ap- tween fresh-gas charge and engine speed as a plications with excess air (λ > 1). limit the torque developed at part load. the air drawn in remains as residual exhaust gas in the cylinder or is forced out during the exhaust stroke. participate in combustion. max. With the throttle (that is. there are no throt- tion. Mechanical supercharging Volumetric efficiency The intake-air density can be further in- For the air throughput. ing level depends on the intake manifold’s This exhaust-gas mass also defines the design and on its operating point (for the amount of inert gas in the fresh cylinder most part. The compressed air is forced through the ton displacement. Dynamic supercharging Valve overlap. . gas flow. The possibility of changing cases.. remaining in the cylinder is considered. one refers to “internal” EGR. process.9. These cams also define the cylinder (supercharging). the theoretical charge as defined by the pis. that is. the overlap of the Supercharging can be achieved simply by opened times of the intake and exhaust taking advantage of the dynamic effects valves. This means which are opened and closed at precisely de. that maximum torque can be increased by fined times by the cams on the camshaft compressing the air before it enters the (valve timing). Exhaust geometry) means that dynamic supercharg- pipe and intake manifold are connected by ing can be applied across a wide operating an EGR valve so that the percentage of inert range to increase the maximum cylinder gas in the cylinder charge can be varied as a charge. the exhaust-gas turbocharger is driven by an exhaust-gas turbine located in the exhaust- The volumetric efficiency for naturally aspi. For the volumetric effi. on engine speed. above 1. intake manifold and into the engine’s cylin- ciency though. Robert Bosch GmbH 14 Gasoline-engine management Cylinder-charge control Exhaust and refill cycle Supercharging The replacement of the used/burnt cylinder The torque which can be achieved during charge (= exhaust gas) by a fresh-gas charge homogenous operation at λ ≤ 1 is propor- takes place using intake and exhaust valves tional to the fresh gas charge. function of the operating point. inside the intake manifold. This leads to an valve-lift characteristic which influences the increase in volumetric efficiency to values exhaust and refill cycle and with it the fresh. creased by compressors which are driven ing a complete working cycle is referred to mechanically from the engine’s crankshaft. the intake-manifold geometry while the The inert-gas mass in the cylinder charge engine is running (variable intake-manifold can be increased by “external” EGR. is not considered.6. rated engines is 0. the opened in the exhaust gas. Exhaust-gas turbocharging which is not available for the combustion In contrast to the mechanical supercharger.. only the exhaust gas actually ders. has a decisive influence on the ex. and the valve timing. Fresh gas drawn in during valve overlap.0. but also on charge for the next power cycle. gas charge which is available for combus- tion. In such cylinder charge). cross-sections of the gas-exchange valves. and not by the engine’s crankshaft. the total charge dur. The supercharg- haust-gas mass remaining in the cylinder. It depends upon This enables recovery of some of the energy the combustion-chamber shape. This fuel is metered to the direct-injection (DI) engines. Or. DI gasoline engines. appropriate to the amount of air drawn into Other combustion conditions prevail on the engine. Ideal. and this marks the point at . The maximum value for tion is also used to achieve an A/F-mixture λ that can be achieved is defined by the distribution which to a great extent prevents so-called lean-misfire limit (LML). distribution. approx. A/F mixture To run efficiently. the A/F mixture in the mani- mass ratio of 14.500 tion in the combustion chamber. This leads to an 14. is plied to achieve this form of A/F-mixture not available for combustion. combustible. Homogeneous (λ ≤ 1): On manifold-injec- cally complete combustion takes place at a tion engines. Homogeneous lean (λ > 1): The A/F mixture viates from the theoretically ideal mass ratio is distributed homogeneously in the com- (14. fuel consumption in- The A/F-mixture formation system is re. (late) injection leads to the rapid warm-up misfire limit the A/F mixture is no longer of the catalytic converter. and an A/F-mixture cloud forms in the λ < 1: This indicates air deficiency and vicinity of the spark plug. Fuel is in- the theoretically required air mass. liters of air are needed to completely burn 1 This operating mode is also possible with liter of gasoline. On a cold en- gine. Stratified-charge/catalyst heating: Retarded ture-formation system used. the fuel being injected into the combustion chamber during the in- Excess-air factor λ duction stroke. the gasoline engine needs Operating modes a given air/fuel (A/F) ratio.7 kg of air are needed to burn 1 kg of essentially homogeneous mixture distribu- fuel. In other words.7:1. expressed in volumes. The engine begins to run very unevenly. Homogenous stratified charge: In addition to ture by adding fuel to compensate for the the stratified charge. during the induction stroke. jected only shortly before the ignition point. highly dependent upon the engine’s design and construction. which is also referred to fold is drawn in past the open intake valve as the stoichiometric ratio. as well as upon the mix. it is necessary to enrich the A/F mix. Robert Bosch GmbH Gasoline-engine management A/F-mixture formation 15 A/F-mixture formation which misfire starts. there is a homogeneous fuel that has condensed on the cold mani. creases dramatically. thus able to run with considerably higher λ figures. as a result. therefore a rich A/F mixture. 9. and these are engine’s cylinders through the fuel injectors. At the lean. λ defines the ratio of the actually bustion chamber with a defined level of ex- supplied air mass to the theoretical air mass cess air. dual injec- a lean A/F mixture. Stratified charge: This operating mode and those given below are only possible with di- λ = 1: The inducted air mass corresponds to rect-injection gasoline engines. lean A/F mixture throughout the complete fold walls (manifold-injection engines) and combustion chamber. The excess-air factor λ has been chosen to indicate how far the actual A/F-mixture de. and is combustion knock.7:1). and power output sponsible for calculating the fuel mass drops. Dual injection is ap- cold cylinder walls and which. theoreti. λ > 1: This indicates excess air and therefore Homogeneous anti-knock: Here. required for complete (stoichiometric) com- bustion. . during homo- (λ = 1.0 1.85). maximum power can only be In order to comply with these requirements.20 % excess air For gasoline direct injection. fuel consump.. Figs. tions apply as with manifold injection. a practi- tion of the excess-air factor λ.4 Excess-air factor λ Excess-air factor λ (excess air) Specific fuel consumption. HC. cannot be reduced by the 3-way catalytic large fuel droplets are deposited on the walls converter. it is ab..6 0. If the fuel is not perfectly atomized. a b æ UMK0033-1E æ UMK0032-1E Figure 1 a Rich A/F mixture (air deficiency) b Lean A/F mixture 0. It is immedi. stratified-charge operation though. it is . they lead to increased HC emis- Manifold-injection gasoline engines develop sions.9. injected. Since these fuel droplets cannot burn Manifold injection completely.1. Regarding the combustion are achieved with excess-air factors of chamber as a whole.0 1. An optimal combustion process though Depending upon the combustion process. in this operating mode. near the spark plug. and the A/F-mixture distribution in the but also a homogeneous A/F mixture. for emissions control..8 1. of the manifold and/or combustion cham- power and exhaust emissions ber. Best-possible fuel consumption combustion chamber is filled with fresh air together with best-possible power output and inert gas.. and their lowest Gasoline direct injection fuel consumption at 10. With tion.15 % air deficiency (λ = 0. the A/F mixture ratio is λ = 0.2 1. developed when the complete combustion the mass of the intake air must be measured chamber is filled with a homogeneous A/F exactly and a precisely metered fuel quantity mixture.. the same condi- tent to which power output. and exhaust emissions are all a func. geneous operation at λ ≤ 1.1. not only demands precision fuel injection. which combustion chamber.2).. the mum”. very high (λ > 1)..0. cally stoichiometric A/F mixture is only pre- ately apparent that there is no excess-air sent in the stratified-charge mixture cloud factor at which all factors are at their “opti. NOX Power P . composition of untreated exhaust gas under con- ditions of homogeneous A/F-mixture distribution ditions of homogeneous A/F-mixture distribution HC NOX CO specific fuel consumption be P Relative quantities of be CO. Similar to mani- precisely when the engine has warmed-up.2 0. 1 and 2 indicate the ex.. NOx emissions are in turn necessitates efficient atomization of generated in the lean-burn mode which the fuel..1. Here. Robert Bosch GmbH 16 Gasoline-engine management A/F-mixture formation 1 Influence of the excess-air factor λ on the power P 2 Effect of the excess-air factor λ on the pollutant and on the specific fuel consumption be under con. their maximum power output at 5. fold injection.1. torque output and solutely imperative that λ = 1 is maintained power output both drop.8 1. Outside this area. Since the complete combustion chamber When a 3-way catalytic converter is used for is not filled with a combustible A/F mixture the treatment of the exhaust gases.95. where is interrupted (overrun fuel cutoff). stratified. to run the engine as often as possible with a stratified-charge. the fuel re. they can be ig- tion gasoline engines though. This also drop in manifold pressure causes a reduc- applies to the gasoline direct-injection en. operating temperature. rect the A/F mixture so as to ensure not only the best possible driveability. and the pronounced wall wet. Robert Bosch GmbH Gasoline-engine management A/F-mixture formation 17 necessary to take additional measures which Full load call for a NOx accumulator-type catalytic Essentially. ating temperature though. sudden deceleration leans to tional fuel must continue to be injected until enrichment of the A/F mixture since the it reaches operating temperature. Engine operating modes it may be necessary to enrich the A/F mix- In some engine operating modes. Depending upon the engine’s design wall film is drawn into the cylinder. the fuel supply the highest potential for saving fuel. wall film. tion in the wall film and the fuel from the gine. Being To compensate for these negative effects. the cylinder walls. This makes it neces- sary to take corrective measures in the A/F. ture. off temporarily until the wall film has stabi- Even after the engine has started. With manifold injection. but also to the fuel as occur when the throttle-valve opening having less tendency to evaporate at low changes suddenly. perature. and the wall film thickens as a result. conventional manifold-injection Wall-film effects are also encountered at engines all run on a stoichiometric A/F mix. jection and gasoline direct injection are pretty much the same at full load. This leads to the de- When starting with the engine cold. Acceleration and deceleration mixture formation. velopment of a fuel film (wall film) on the ducted A/F-mixture leans-off. lized. Apart fuel savings of as much as 40 % can be from saving fuel on downhill gradients. At WOT. As can be seen from Fig. . Heavy acceleration causes the in- ting (condensation of the fuel) on the still. the in. this permits quirement differs considerably from the the generation of maximum-possible torque steady-state requirements with the engine at and power. addi. valves. this achieved with lean-burn operation. On direct-injec. perature-dependent correction function charge lean-burn operation is only possible (transitional compensation) is used to cor- with the engine at operating temperature. the fuel’s evaporation tendency deteriorates. but also the Idle and part load constant A/F ratio as needed for the catalytic Once they have reached their operating tem. take air with the fuel. take-manifold pressure to increase so that cold intake manifold (only on manifold-in. This is the intake manifold in the vicinity of the intake due not only to inadequate mixing of the in. With the engine at oper- ture at idle and part load. the fuel’s tendency to evaporate depends to a large extent upon Start and warm-up the manifold pressure. 1. converter. the A/F mixture leans- be provided during the cranking process. the objective is nored on direct-injection gasoline engines. Rapid changes in manifold pressure. and as a portion of the fuel has been deposited to facilitate engine start. additional fuel must to form the wall film. jection engines) and on the cylinder walls. the two operating modes with At overrun (trailing throttle). lead to changes in this temperatures. protects the catalytic converter against over- heating which could result from inefficient and incomplete combustion. Similarly. the conditions for manifold in- converter. A tem- and the combustion process. This is feasible at idle and Overrun at part load. the ignition map (Fig. The map’s 1 Ignition map based on engine rpm n and relative data points are formed by a given number of air charge rl values. air cative pm ine r harg Eng e These ignition maps are generated by running the engine on the engine dynamometer. cylinder charge on the ignition angle. and represents the basic adap- nying pressure peaks in the cylinder. with a In the gasoline (SI) engine. of the spark plug. the ignition coil to recharge it. The lower the cylinder charge the slower is the flame Ignition system front’s propagation. By applying linear inter- polation between two data points. the A/F mixture low cylinder charge. therefore. whereby care must be taken that con- electronically controlled. data storage. Along with increas- ing engine speed. the ignition an- It is the job of the ignition to ignite the com. It determines coil. the ignition angle must is ignited by a spark between the electrodes also be advanced. typically 16. pressed A/F-mixture at exactly the right mo. The inductive-type igni- tion systems used predominantly on gaso. about 2 milliseconds are count the influence of engine speed and needed for the A/F mixture to burn com. Using the ignition-map principle for the electronic control of the ignition angle means that for every engine operating point it is possible to select the best-possible igni- æ UMZ0030-1E Rel tion angle. This energy determines how long (dwell angle) the current must flow through
The delivered torque. fect upon the combustion curve. gle must be shifted in the advance direction. the num- ber of ignition-angle values is increased to 4096. the processes quirements are complied with as well as pos- behind the ignition of the A/F mixture are sible. . Ignition point Ignition angle: Basic adaptation Changing the ignition point On electronically controlled ignition sys- (ignition timing) tems. Robert Bosch GmbH 18 Gasoline-engine management Ignition Ignition place shortly after TDC. For this reason. shaft angle (ignition angle) leads to the igni- tion spark and the A/F-mixture combustion. The interrup. The ignition point must be selected map is stored in the engine-management so that main combustion. A certain ignition angle is allocated to each pair of variates so that the map has 256 (16x16) adjustable igni- Ignition angle tion-angle values. Influence of the ignition angle line engines store the electrical energy The ignition angle has a decisive influence needed for the ignition spark in the ignition on engine operation. and the accompa. and tion of the coil current at a defined crank.
The fuel consumption. This pletely.
The exhaust-gas emissions. The ignition angle is chosen so that all re- In today’s ignition systems. The cylinder charge (or fill) also has an ef- ment in time and thus initiate its combustion. The x and y axes represent the engine speed and the relative air charge. takes tation of the ignition angle. 1) takes into ac- Following ignition. tinued engine knock is avoided. bustion knock only takes place in homoge- neous operation. the basic adaptation of the ignition angle age in the form of fixed values or character. Such corrections are stored in the data stor. time required to generate the required igni- ular combustion has started. tarded at the cylinder concerned. the ignition takes place too early. time. which demand an ignition in the stratified charge at the combustion angle which deviates from those defined by chamber’s peripheral zones. The energy stored in the ignition coil is a function of the length of time current flows Knock control through the coil (energisation time). and when the engine is not making too the x and y axes of which represent rpm and much noise. They shift the basic ignition an- gle by the stipulated amount in either the On direct-injection gasoline engines. Robert Bosch GmbH Gasoline-engine management Ignition 19 Additive ignition-angle adjustments If knock continues over a longer period of A lean A/F mixture is more difficult to ig. In such cases. it is then audible as combustion battery voltage. therefore. To obtain gle corrections are therefore also necessary.g. To prevent knock on today’s high- reached. A lean A/F mixture must therefore compression engines. knock sensors detect the able which affects the choice of the ignition start of knock and the ignition angle is re- angle. In or- Knock is a phenomenon which occurs when der not to thermally overload the coil. the engine can be damaged by the nite. no matter whether of be ignited sooner. The coolant temperature is a further vari. access is made to special ignition-angle curves stored Dwell angle in the data storage. This means that more time is needed pressure waves and the excessive thermal before the main combustion point is loading. type. Here. and for this reason the bat- a considerable local pressure increase. once reg. residual mixture which has not been reached by the flame front. through the combustion chamber until it hits the cylinder wall. At high speeds. temperature-dependent knock limit. the ignition map. correction). the rapid pres. (ignition map) can be located directly at the istic curves (e. tion energy in the coil must be rigidly ad- sure increase in the combustion chamber hered to. This tery voltage must be taken into account generates a pressure wave which propagates when calculating the dwell angle. The dwell angle refers to the crank- leads to the auto-ignition of the unburnt shaft and is therefore speed-dependent. . knock control belongs to the standard scope of the engine-management system. the best-possible engine efficiency. There is no tendency for Special ignition angle the engine to knock in the stratified-charge There are certain operating modes. The resulting abrupt The ignition-coil current is a function of the combustion of the residual mixture leads to battery voltage. With this system. the engine noises blanket the combustion knock. At low engine speeds The dwell-angle values are stored in a map. Temperature-dependent ignition-an. such as mode since there is no combustible mixture idle and overrun. knock. com- advance or retard direction. The A/F ratio λ thus has the manifold-injection or direct-injection an influence on the ignition angle. ferred to the throttle valve by a linkage (2) cial importance but also the systems which or by a Bowden cable. as well as on direct-injection This information is inputted to the ECU (8) engines operating on a homogeneous A/F in the form of an electrical signal (9). In both cases though. On engines the A/C compressor is switched on more air with external A/F-mixture formation (mani. Another method tract controls the air flow drawn in by the uses a throttle-valve actuator to adjust the engine and thus also the cylinder charge. Robert Bosch GmbH 20 Systems for cylinder-charge control Air-charge control Systems for cylinder-charge control On a gasoline engine running with a homo. This means that accelerator-pedal (1) movement is trans- not only is the fuel-metering system of spe. And when. in by the engine. engine takes from the intake air. the intake air is the Conventional systems (Fig. Air-charge control To compensate for the higher levels of fric- tion. fuel needs oxygen which the mass and extra fuel. The therefore for engine power. and with it the torque out- put. for instance. Conventional systems geneous A/F mixture. and mixture with λ = 1. the output torque is di. 1) feature a me- decisive quantity for the output torque and chanically operated throttle valve (3). is needed to compensate for the torque loss. The throttle valve’s influence the cylinder charge. 1 Principle of the air control in a conventional system using a mechanically adjustable throttle valve and an air bypass actuator 1 2 Figure 1 1 Accelerator pedal 5 4 3 2 Bowden cable or linkage 3 Throttle valve 6 4 Induction passage 8 7 5 Intake air flow 6 Bypass air flow æ UMK1677-1Y 7 Idle-speed actuator 9 (air bypass actuator) 8 ECU 9 Input variables (elec- trical signals) . it is only possible to electronically influence the air flow needed by the engine to a limited extent. the extra air is supplied by the air bypass ac- rectly dependent upon the intake-air mass. Some of these variable opening angle alters the opening systems are able to influence the percentage cross-section of the intake passage (4) and of inert gas in the cylinder charge and thus in doing so regulates the air flow (5) drawn also the exhaust emissions. for instance for idle- speed control. fold injection). throttle valve’s minimum stop. tuator (7) directing the required extra air (6) The throttle valve located in the induction around the throttle valve. the cold engine requires a larger air For it to burn. the (5). Pos. in other words the driver input.) the engine control unit. unit. an ECU (Fig. They can be complied with though thanks to ETC with its possibilities of further im- Using the feedback information from the proving the A/F-mixture composition. throttle-valve-angle sensor regarding the ETC is indispensable when complying current position of the throttle valve. The DC-motor throttle-valve drive (4) throttle valve is immediately shifted to a pre- and the throttle-valve-angle sensor (3) are determined position (emergency or limp- combined with the throttle valve to form a home operation). . is the ETC control is integrated in the engine registered by two potentiometers (accelera. In case malfunctions are known as EGAS). the throttle-valve drive. Robert Bosch GmbH Systems for cylinder-charge control Air-charge control 21 2 The ETC system (Electronic Throttle Control or EGAS) 1 2 Sensors Actuators 3 4 5 CAN C M Monitoring Figure 2 modul 1 Accelerator-pedal sensor 2 Engine ECU æ UMK1627-1E 3 Throttle-valve-angle sensor 4 Throttle-valve drive Accelerator-pedal Engine ECU Throttle device (DC motor) module 5 Throttle valve ETC systems The potentiometers are duplicated for re- With ETC (Electronic Throttle Control. and the auxiliary engine’s actual operating status (engine functions. the accelerator-pedal po. sition. In the latest engine-management systems. 1). engine temperature. fuel injection. ECU then calculates the throttle-valve open- ing which corresponds to the driver input The demands of emissions-control legisla- and converts it into a triggering signal for tion are getting sharper from year to year. ECU which is also responsible for control- tor-pedal sensor. it then with the demands made by gasoline direct becomes possible to precisely adjust the injection on the overall vehicle system. To trigger the throttle device. also dundancy reasons. etc. 2) is detected in that part of the system which is responsible for controlling the throttle valve decisive for the engine’s power output. throttle valve to the required setting. the so-called throttle device. Two potentiometers on the accelerator-pedal and two on the throttle unit are a compo- nent part of the ETC monitoring concept. Taking into account the ling ignition. There is no longer a separate ETC speed. 2. Robert Bosch GmbH 22 Systems for cylinder-charge control Variable valve timing Variable valve timing Camshaft phase adjustment In conventional IC engines, camshaft and Apart from using the throttle-valve to throt- crankshaft are mechanically coupled to each tle the flow of incoming fresh gas drawn in other through toothed belt or chain. This by the engine, there are several other possi- coupling is invariable. bilities for influencing the cylinder charge. On engines with camshaft adjustment, at The proportion of fresh gas and of residual least the intake camshaft, but to an increas- gas can also be influenced by applying vari- ing degree the exhaust camshaft as well, can able valve timing. be rotated referred to the crankshaft so that valve overlap changes. The valve opening Of great importance for valve timing is the period and lift are not affected by camshaft fact that the behaviour of the gas columns phase adjustment, which means that “intake flowing into and out of the cylinders varies opens” and “intake closes” remain invariably considerably as a function of engine speed coupled with each other. or throttle-valve opening. With invariable The camshaft is adjusted by means of valve timing, therefore, this means that the electrical or electro-hydraulic actuators. On exhaust and refill cycle can only be ideal for less sophisticated systems provision is only one single engine operating range. Variable made for two camshaft settings. Variable valve timing, on the other hand, permits camshaft adjustment on the other hand per- adaptation to a variety of different engine mits, within a given range, infinitely variable speeds and cylinder charges. This has the adjustment of the camshaft referred to the following advantages: crankshaft. Fig. 1 shows how the “position”, or lift, of
Higher engine outputs, the open intake-valve changes (referred to
Favorable torque curve throughout a wide TDC) when the intake camshaft is adjusted. engine-speed range,
Reduction of toxic emissions, Retard adjustment of the intake camshaft
Reduced fuel consumption, Retarding the intake camshaft leads to the
Reduction of engine noise. intake valve opening later so that valve over- lap is reduced, or there is no valve overlap at all. At low engine speeds (<2000 min–1), this 1 Camshaft adjustment results in only very little burnt exhaust gas flowing past the intake valve and into the Exhaust intake manifold. At low engine speeds, the (invariable) Intake low residual exhaust-gas content in the in- (variable) take of A/F mixture which then follows leads to a more efficient combustion process and a A smoother idle. This means that the idle speed can be reduced, a step which is partic- ularly favorable with respect to fuel con- Valve lift s 1 sumption. 2 3 æ UMM0534-1E Figure 1 0 1 Camshaft retarded 300° 360° 420° 480° 540° 600° 2 Camshaft normal TDC BDC 3 Camshaft advanced Crankshaft angle A Valve overlap Robert Bosch GmbH Systems for cylinder-charge control Variable valve timing 23 The camshaft is also retarded at higher en- The higher inert-gas content in the cylinder gine speeds (>5,000 min–1). Late closing of charge makes it necessary to open the the intake valve, long after BDC, leads to a throttle valve further, which in turn leads to higher cylinder charge. This boost effect re- a reduction of the throttling losses. This sults from the high flow speed of the fresh means that valve overlap can be applied to gas through the intake valve which contin- reduce fuel consumption. ues even after the piston has reversed its di- rection of travel and is moving upwards to Adjusting the exhaust camshaft compress the mixture. For this reason, the On systems which can also adjust the ex- intake valve closes long after BDC. haust camshaft, not only the intake camshaft is used to vary the residual-gas content, but Advance adjustment of the intake camshaft also the exhaust camshaft. Here, the total In the medium speed range, the flow of fresh cylinder charge (defined by “intake closes”) gas through the intake passage is much and the residual-gas content (influenced by slower, and of course there is no high-speed “intake opens” and “exhaust closes”) can be boost effect. controlled independently of each other. At medium engine speeds, closing the intake valve earlier, only shortly after BDC, pre- Camshaft changeover vents the ascending piston forcing the Camshaft changeover (Fig. 2) involves freshly drawn-in gas out past the intake switching the camshaft between two differ- valve again and back into the manifold. At ent cam contours. This changes both the such speeds, advancing the intake camshaft valve lift and the valve timing (cam-contour results in better cylinder charge and there- changeover). The first cam defines the opti- fore a good torque curve. mum timing and the valve lift for the intake and exhaust valves in the lower and medium At medium speeds, advanced opening of the speed ranges. The second cam controls the intake camshaft leads to increased valve increased valve lift and longer valve-open overlap. Opening the intake valve early times needed at higher speeds. means that shortly before TDC, the residual At low and medium engine speeds, mini- exhaust gas which has not already left the mum valve lifts together with the associated cylinder is forced out past the open intake valve and into the intake manifold by the as- 2 Camshaft changeover cending piston. These exhaust gases are then drawn into the cylinder again and serve to increase the residual-gas content of the Exhaust Intake cylinder charge. The increased residual gas (variable) (variable) content in the freshly drawn in A/F mixture caused by advancing the intake camshaft, af- 2 2 fects the combustion process. The resulting lower peak temperatures lead to a reduction Valve lift s in NOx. 1 1 æ UMM0535-1E 0 120° 240° 360° 480° 600° BDC TDC BDC Figure 2 Crankshaft angle 1 Standard cam 2 Supplementary cam Robert Bosch GmbH 24 Systems for cylinder-charge control Variable valve timing Fully variable valve timing and valve lift 3 Example of a system with fully variable ad- justment of valve timing and of valve lift using the camshaft Valve control which incorporates both vari- able valve timing and variable valve lift is re- a b ferred to as being fully variable. Even more freedom in engine operation is permitted by 3D cam contours and longitudinal-shift camshafts (Fig. 3). With this form of camshaft control, not only the valve lift (only on the intake side) and thus the open- ing angle of the valves can be infinitely var- ied, but also the phase position between æ UMM0536-1Y camshaft and crankshaft. Since the intake valve can be closed early Figure 3 with this fully variable camshaft control, this a Minimum lift permits so-called charge control in which b Maximum lift the intake-manifold throttling is consider- ably reduced. This enables fuel consumption small valve-opening cross-sections lead to a to be slightly lowered in comparison with high inflow velocity and therefore to high the simple camshaft phase adjustment. levels of turbulence in the cylinder for the fresh air (gasoline direct injection) or for the Fully variable valve timing and valve lift fresh A/F mixture (manifold injection). This without using the camshaft ensures excellent A/F mixture formation at For valve timing, maximum design freedom part load. The high engine outputs required and maximum development potential are at higher engine speeds and torque demand afforded by systems featuring valve-timing (WOT) necessitate maximum cylinder control which is independent of the charge. Here, the maximum valve lift is camshaft. With this form of timing, the selected. valves are opened and closed, for instance, by electromagnetic actuators. A supplemen- There are a variety of methods in use for tary ECU is responsible for triggering. This switching-over between the different cam form of fully variable valve timing without contours. One method, for instance, relies camshaft aims at extensive reduction of the on a free-moving drag lever which engages intake-manifold throttling, coupled with with the standard rocking lever as a function very low pumping losses. Further fuel sav- of rotational speed. Another method uses ings can be achieved by incorporating cylin- changeover cup tappets. der and valve shutoff. These fully variable valve-timing concepts not only permit the best-possible cylinder charge and with it a maximum of torque, but they also ensure improved A/F-mixture formation which results in lower toxic emis- sions in the exhaust gas. Robert Bosch GmbH Systems for cylinder-charge control Exhaust-gas recirculation (EGR) 25 Exhaust-gas recirculation EGR with gasoline direct injection EGR is also used on gasoline direct-injection (EGR) engines to reduce NOx emissions and fuel consumption. In fact, it is absolutely essen- The mass of the residual gas remaining in tial since with it NOx emissions can be the cylinder, and with it the inert-gas con- lowered to such an extent in lean-burn oper- tent of the cylinder charge, can be influ- ations that other emissions-reduction mea- enced by varying the valve timing. In this sures can be reduced accordingly (for case, one refers to “internal” EGR. The inert- instance, rich homogeneous operation for gas content can be influenced far more by NOx “Removal” from the NOx accumulator- applying “external” EGR with which part of type catalytic converter). EGR also has a the exhaust gas which has already left the favorable effect on fuel consumption. cylinder is directed back into the intake There must be a pressure gradient be- manifold through a special line (Fig. 1, tween the intake manifold and the exhaust- Pos. 3). EGR leads to a reduction of the NOx gas tract in order that exhaust gas can be emissions and to a slightly lower fuel-con- drawn in via the EGR valve. At part load sumption figure. though, direct-injection engines are oper- ated practically unthrottled. Furthermore a Limiting the NOx emissions considerable amount of oxygen is drawn Since they are highly dependent upon tem- into the intake manifold via EGR during perature, EGR is highly effective in reducing lean-burn operation. NOx emissions. When peak combustion Non-throttled operation and the intro- temperature is lowered by introducing burnt duction of oxygen into the intake manifold exhaust gas to the A/F mixture, NOx emis- via the EGR therefore necessitate a control sions drop accordingly. strategy which coordinates throttle valve and EGR valve. This results in severe demands Lowering fuel consumption being made on the EGR system with regard When EGR is applied, the overall cylinder to precision and reliability, and it must be charge increases while the charge of fresh air robust enough to withstand the deposits remains constant. This means that the throt- which accumulate in the exhaust-gas com- tle valve (2) must reduce the engine throt- ponents as a result of the low exhaust-gas tling if a given torque is to be achieved. Fuel temperatures. consumption drops as a result. 1 Exhaust-gas recirculation (EGR) EGR: Operating concept Depending upon the engine’s operating 4 point, the engine ECU (4) triggers the EGR n valve (5) and defines its opened cross-sec- rl tion. Part of the exhaust-gas (6) is diverted via this opened cross-section (3) and mixed 5 with the incoming fresh air. This defines the 3 3 Figure 1 exhaust-gas content of the cylinder charge. 1 2 1 Fresh-air intake 6 2 Throttle valve 3 Recirculated exhaust gas 4 Engine ECU æ UMK0913-2Y 5 EGR valve 6 Exhaust gas n Engine rpm rl Relative air charge For this reason. sponse. With MPI. the length and to trigger a return pressure wave. In the intake manifold. the pres. hand. The piston’s the intake-manifold geometry and the en- induction work causes the open intake valve gine speed. At the diameter of the individual tubes is matched open end of the intake manifold. The resulting pressure fluctuations at prove the cylinder charge. This is the reason for there be- ing no problems with multipoint injection æ UMM0587Y Figure 1 systems regarding the even distribution of 1 1 Cylinder 2 Individual tube fuel. The pressure waves are able to propagate in the The exhaust-and-refill processes are not individual tubes independently. In the case of multipoint injection (MPI). Robert Bosch GmbH 26 Systems for cylinder-charge control Dynamic supercharging Dynamic supercharging Ram-tube supercharging The intake manifolds for multipoint injec- Approximately speaking. or it is injected directly into the combustion 3 chamber (gasoline direct injection). content in the cylinder charge. 1). but also The supercharging effect depends upon by the intake and exhaust lines. since the intake manifolds transport mainly air and practically no fuel can de- posit on the manifold walls. Long. each cylinder is allocated its own to a certain extent by compressing the air tube (2) of specific length which is usually before it enters the cylinder. large-diameter tubes have a This supercharging effect thus depends on positive effect on the torque curve at higher utilization of the incoming air’s dynamic re. tion systems are composed of the individual gine torque is proportional to the fresh-gas tubes or runners and the manifold chamber. short. the fuel 4 is either injected into the intake manifold onto the intake valve (manifold injection). 3 Manifold chamber 4 Throttle valve . On the other highest-possible torque. engine speeds. to the valve timing so that in the required sure wave encounters the quiescent ambient speed range a pressure wave reflected at the air from which it is reflected back again so end of the tube is able to enter the cylinder that it returns in the direction of the intake through the open intake valve (1) and im- valve. the dynamic effects depend upon the geometrical rela- tionships in the intake manifold and on the engine speed. only influenced by the valve timing. the achievable en. attached to the manifold chamber (3). narrow the intake valve can be utilized to increase tubes result in a marked supercharging ef- the fresh-gas charge and thus achieve the fect at low engine speeds. For the even distribution of the A/F mixture. this provides 2 wide-ranging possibilities for intake-mani- fold design. the intake manifolds for carburetor engines and single-point injection (TBI) must have short pipes which as far as possible must be 1 Principle of ram-tube supercharging of the same length for all cylinders. This means In the case of ram-tube supercharging that the maximum torque can be increased (Fig. mum charge (volumetric efficiency). The chambers. Robert Bosch GmbH Systems for cylinder-charge control Dynamic supercharging 27 Tuned-intake-tube charging Variable-geometry intake manifold At a given engine speed. The two systems This results in a further increase of pressure just dealt with increase the achievable maxi- and leads to an additional supercharging ef.
Switch over between different intake-tube ders each with its own tuned intake tube lengths or different tube diameters. On the tuned intake-tube system (Fig. sequence. the engine’s working point. prevents the overlapping of the flow
Selected switchoff of one of the cylinder’s processes of two neighboring cylinders intake tubes on multiple-tube systems. from dynamic supercharging depends upon column to vibrate at resonant frequency. as a function of the en- tubes (2). are con. tional intake mani- fold . flaps are used to im- nected through tuned intake tubes (4) with plement a variety of different adjustments either the atmosphere or with the manifold such as: chamber (5) and function as Helmholtz res- onators. dy- namic-response errors can occur in some cases when the load is changed abruptly. the periodic piston The supplementary cylinder charge resulting movement causes the intake-manifold gas. in turn. these variable-geometry systems. above fect. 2 Principle of tuned-intake-tube charging 3 Increasing the maximum-possible cylinder air charge (volumetric efficiency) by means of dynamic supercharging Figure 2 1 Cylinder 2 Short tube 6 1 3 Resonance chamber 5 4 Tuned intake tube 5 Manifold chamber 4 6 Throttle valve Volumetric efficiency 2 A Cylinder group A B Cylinder group B 3 2 Figure 3 æ UMM0588Y æ UMM0589E 1 1 3 1 System with tuned- 1 4 2 4 1 intake-tube charging 2 System with conven- n A B Engine speed n nom. which are adjacent to each other in the firing
Switchover to different chamber volumes. The length of the tuned intake tubes and Electrical or electropneumatically actuated the size of the resonance chamber are a flaps are used for change-over operations in function of the speed range in which the su. all in the low engine-speed range (Fig. The subdivision into two groups of cylin. percharging effect due to resonance is re- quired to be at maximum. groups of cylinders (1) with identical an. Due to the accu- mulator effect of the considerable chamber volumes which are sometimes needed. Practically ideal torque characteristics can gular ignition spacing are each connected to be achieved with variable-geometry intake a resonance chamber (3) through short manifolds in which. gine operating point. 2).
Adjustment of the intake-tube length. 3). the lower speed range. 4 can tibutes to improved cylinder charge at high switch between two different ram tubes. A single in- 3 with changeover flap take-air chamber with a high resonant open b 2 4 1 1 Changeover flap frequency is then formed for the short ram 2 Manifold chamber tubes (2). tube The low resonant frequency is then defined æ UMM0590Y 4 Changeover flap by the long tuned intake tube (4). the changeover flap (1) is closed and the intake air flows to the Tuned-intake-tube system cylinders through the long ram tube (3). changeover flap is closed and the system row-diameter ram functions as a tuned-intake-tube system. one speaks of a combined tuned-in- b Manifold geometry take-tube and ram-tube system. opened: Short. wide-diameter ram tube Figure 5 1 Cylinder 2 Ram tube 5 Combined tuned-intake-tube and ram-tube system (short intake tube) 3 Resonance chamber 4 Tuned intake tube 6 5 Manifold chamber 5 6 Throttle valve 7 Changeover flap 4 A Cylinder group A 7 B Cylinder group B 3 2 a Intake-manifold con- 1 ditions with changeover flap a A B b æ UMM0591Y closed b Intake-manifold con- ditions with changeover flap open . The changed open. 5. 3 Changeover flap At low and medium engine revs. and thus con- The manifold system shown in Fig. Combined tuned-intake-tube and ram-tube system Figure 4 When design permits the open changeover a Manifold geometry flap (Fig. geometry of this configuration has an effect upon the resonant frequency of the intake 4 Ram-tube system system. At Opening the resonance flap switches in a higher speeds and with the changeover flap second tuned intake tube. the closed: Long. Robert Bosch GmbH 28 Systems for cylinder-charge control Dynamic supercharging Ram-tube systems wide diameter ram tube (4). nar. 7) to combine both the res- with changeover flap onance chambers (3) to form a single vol- closed ume. the intake air flows through the short. Cylinder charge in the lower speed range is improved by the higher effective volume resulting from the second tuned in- a 2 1 take pipe. In engine revs. Pos. a bypass can be applied to control the boost pressure. Mechanically driven com. perchargers with different types of construc- tion (e. engine and compressor able to switch off the compressor via a speeds are directly coupled to one another clutch at low engine loading. A portion of the compressd air is directed into the cylinder and the remainder is re- turned to the supercharger input via the by- pass. sliding-vane Since the power required to drive the com- supercharger. pressor is not available as effective engine screw-type supercharger). 1 Rotary-screw supercharger: Principle of functioning 1 æ UMM0592Y Figure 1 2 1 Intake air 2 Compressed air .g. or they are cen. Boost-pressure control On the mechanical supercharger. the direct Design and operating concept coupling between compressor and engine The application of supercharging units leads crankshft means that when engine speed in- to increased cylinder charge and therefore to creases there is no delay in supercharger ac- increased torque. The engine management is responsible for controlling the bypass valve. better. Robert Bosch GmbH Systems for cylinder-charge control Mechanical supercharging 29 Mechanical supercharging Advantages and disadvantages On the mechanical supercharger. through a belt drive. the above advantage is counteracted trifugal turbo-compressors (e. torque is higher and dynamic response is pressors are either positive-displacement su. This disadvantage though is somewhat al- charger with the two counter-rotating screw leviated when the engine management is elements.g. power. As a rule. This means therefore. functioning of the rotary-screw super. radial-flow by a slightly higher fuel-consumption figure compressor). Fig. Mechanical supercharging celeration. spiral-type supercharger. that com- uses a compressor which is driven directly pared to exhaust-gas turbocharging engine by the IC engine. 1 shows the principle of compared to the exhaust-gas turbocharger. Roots supercharger. Robert Bosch GmbH 30 Systems for cylinder-charge control Exhaust-gas turbocharging Exhaust-gas turbocharging Design and operating concept The main components of the exhaust-gas Of all the possible methods for supercharg. pressurized exhaust gas. 7) are applied ra- speeds. in the past. exhaust-gas super. 1) are the exhaust-gas ing the IC engine. turbine is for the most part taken from the hot. This holds true particularly in com. are mounted on a common shaft (2). it is today generate the required compressor power. 1 Passenger-car exhaust-gas turbocharger (Shown: 3K-Warner. exhaust gas when it leaves the engine so as to creased power-weight ratio. energy must be also used to “dam” the bocharging was applied in the quest for in. type K14) 4 Figure 1 1 Compressor impeller 5 2 Shaft 3 Exhaust-gas turbine æ SMM0593Y 4 Intake for exhaust- gas mass flow 5 Outlet for com- pressed air 1 2 3 . cause this to rotate at very high speed. The trol. mostly used in order to increase the maxi- mum torque at low and medium engine The hot gases (Fig. hand. charging leads to high torques and power outputs together with high levels of engine The energy needed to drive the exhaust-gas efficiency. Even on engines compressor impeller and the turbine rotor with low swept volumes. turbine-rotor blades are inclined towards the center and thus direct the gas to the in- side from where it then exits axially. On the other Whereas. dially to the exhaust-gas turbine (4) and bination with electronic boost-pressure con. 2. turbine (3) and the compressor (1). turbocharger (Fig. Pos. exhaust-gas turbocharg. The ing is the most widely used. exhaust-gas tur. The VTG (Variable Turbine Geometry) is another method which can be applied to Since the exhaust-gas turbocharger is lo. for in. With high ex. This flap-type bypass valve is usually 2 Design and construction of an exhaust-gas turbo- integrated into the turbine casing. the exhaust-gas mass flow in the turbine bine and into the exhaust system in order reaches a high speed and in doing so also that the turbocharger is prevented from brings the exhaust-gas turbine up to high overcharging the engine. percharger is state-of-the-art on diesel en- tant materials. the required boost pressure. but here the flow conditions are portion of the exhaust-gas mass flow used to reversed. 6 p2 control valve sor (BPS). information on 2 5 Fresh incoming air pD 6 Boost-pressure which is provided by the boost-pressure sen. Diversion is via a speed (Fig. The tur. limit the exhaust-gas mass flow at higher en- cated directly in the flow of hot exhaust gas gine speeds (Fig. 3. 3a). the pulse 8 Wastegate valve is triggered so that a somewhat lower 9 Bypass duct pressure prevails in the control line. charger using a wastegate turbocharger as an example The wastegate is actuated by the boost-pres- sure control valve (6). The Triggering signal for boost-pressure control valve then closes the pulse valve VT 7 VT Volume flow wastegate and the proportion of the ex- through the turbine haust-gas mass flow used to power the tur. to stance WOT at ≤ 2000 min–1. By varying the geometry. 3 7 Exhaust gas If the boost pressure is too low. part of they open up a small cross-section so that the flow must be diverted around the tur. the boost pressure is 9 wastegate excessive. 4 VWG VWG Volume flow bine is increased. 8 æ UMK1320-1Y through the If. At low speeds. line gered by an electrical signal from the engine 1 3 Compressor ECU. axially at the center of the compressor and is forced radially to the outside by the blades VTG turbocharger and compressed in the process. This valve is con- Figure 2 nected pneumatically to the pulse valve (1) 5 1 Pulse valve through a control line (2). but has not yet become successful on gasoline engines due to the high thermal Exhaust-gas turbochargers: Designs stressing resulting from the far hotter ex- Wastegate supercharger haust gases. the so-called wastegate (Fig. The objective is for IC engines to develop high torques at low engine speeds. the pulse valve is triggered so that p2 Boost pressure a somewhat higher pressure is built up in pD Pressure on the the control line. low level of exhaust-gas mass flow. The VTG su- it must be built of highly temperature-resis. The boost-pressure control valve diaphragm . and with it the gas pressure at the turbine. bypass valve. next page). The fresh incoming gas (5) enters power the turbine is reduced. the adjustable bine casing has therefore been designed for a guide vanes (3) adapt the flow cross-section. haust-gas mass flows in this range. on the other hand. Pos. gines. This electrical signal is a function of 4 Exhaust-gas turbine the current boost pressure. 2. 8). Robert Bosch GmbH Systems for cylinder-charge control Exhaust-gas turbocharging 31 The compressor (3) also turns along with valve then opens the wastegate and the pro- the turbine. The pulse valve 2 Pneumatic control changes the boost pressure upon being trig. ingly. and with it the boost pressure. control sleeve (4). Robert Bosch GmbH 32 Systems for cylinder-charge control Exhaust-gas turbocharging At high engine speeds. ric adjustment cell (5) using either vacuum Using the bypass channel (5) incorpo- or overpressure. 3b). best-possible level in accordance with the The control sleeve is adjusted by the en- engine’s operating mode. Figure 3 3 Variable Turbine Geometry of the VTG supercharger 4 Turbine geometry of the VST supercharger a Guide-vane setting for high boost pres- sure a 1 2 3 4 5 a 1 2 3 4 5 6 b Guide-vane setting for low boost pres- sure 1 Exhaust-gas turbine 2 Adjusting ring 3 Guide vanes 6 4 Adjusting lever 5 Barometric cell 6 Exhaust-gas flow – High flow speed – Low flow speed b b Figure 4 a Only 1 flow passage open b Both flow passages open 1 Exhaust-gas turbine 2 1st flow passage æ UMM0552-1Y æ UMM0594Y 3 2nd flow passage 4 Special control sleeve 5 Bypass duct 6 Adjustment fork . gine management via a barometric cell. This adjustment mecha. Pos. means of successively opening two flow pas- sive speeds (Fig. 2 and 3) using a special pressure. vanes. This limits the boost sages (Fig. the guide vanes are adjusted to the de. Initially. in high exhaust-gas flow speed and high tur- Here. it is also possible nism is triggered by the engine management to divert part of the exhaust-gas mass flow so that the boost pressure can be set to the past the exhaust-gas turbine. the adjustable guide VST supercharger vanes (3) open up a larger cross-section so On the VST (Variable Sleeve Turbine) super- that more exhaust gas can enter without ac. the “turbine size” is adapted by celerating the exhaust-gas turbine to exces. or by adjusting cam. As soon as the permissible sired angle either directly through individual boost pressure is reached. the control sleeve adjusting levers (4) attached to the guide successively opens the second flow passage. rated in the turbine casing. charger. only one flow passage is opened. 4. It is an easy matter to adjust the guide-vane and the small opening cross-section results angle by rotating the adjusting ring (2). bine speeds (1). The adjusting the exhaust-gas flow speed reduces accord- ring is rotated pneumatically via a baromet. this results in a higher output (A
B). peller and/or the air-mass flow. including a turbocharger with electric motor. Figure 5 teristic at WOT. At part load. this is evinced by the turbo put power.
Reduced thermal loading of the pistons. Intercooling The low torque that is available at very low The air warms up in the compressor during engine speeds is a disadvantage of the tur. extra compressor driven by an electric mo. warmed tion. power engine speed A curve 4 compared to curve 3). flow. or with an
Reduced tendency to knock. even in the medium-speed range. of a naturally aspirated engine gine with the same output power. the major advantages are to be found in the tur- bocharged engine’s lower weight and smaller 2 1 size (“downsizing”). 5. The drop in the combustion-air tempera- The effects of this flat spot can be min. this tem- enough energy in the exhaust gas to drive perature rise has a negative effect upon the exhaust-gas turbine. This is gines with this facility. This supports the supercharger’s during the compression cycle. these accelerate the compressor im. an increase in the cylinder charge so that it is gas mass flow. and in doing
Lower NOx emissions. In such speed ranges. so avoid the turbo flat spot. intercooling 33 Exhaust-gas turbocharging: 5 Power and torque characteristics of an exhaust- Advantages and disadvantages gas-turbocharged engine compared with those Compared with a naturally-aspirated IC en. Engine speed n/nnom gine in transient sumption figures even though turbocharged (dynamic) engines in fact feature less favorable effi.
Improved thermal efficiency resulting in tor. 4 Supercharged en- 5 gine in steady-state the throttle valve must be opened further. intercooling results in due to the delay in building up the exhaust. When accelerating from low possible to further increase torque and out- engine speeds. at a engine speed given speed. . cylinder charge. there is not has a lower density than cold air. 3 Naturally aspirated generates the required power as shown in 4 engine in steady- Fig. operation and the working point is shifted to an area 5 Torque curve of the æ SMM0595-E with reduced frictional and throttling losses 1/4 1/2 3/4 1 supercharged en- (C
B). the air must therefore be cooled off again by the torque curve is less favorable than that of the intercooler. All in all. but since warm air bocharger. following advantages: ber of other versions available. There are a num. 2. ture also leads to a reduction in the temper- imised by making full use of dynamic ature of the cylinder charge compressed charge. The compressed. Robert Bosch GmbH Systems for cylinder-charge control Exhaust-gas turbocharging. operation ciency figures due to their lower compres- sion ratio. 5 (B or C) at lower engine speeds than 3 state operation Torque M the naturally aspirated engine. the compression process. Compared to supercharged en- natually aspirated engine (curve 5). Identical Due to its more favorable torque charac. In transient opera. The turbocharged en- gine’s torque characteristic is better B C Power output P Same power Extra output at lower throughout the usable speed range (Fig. This results in lower fuel-con. the turbocharged engine 1. Independent of the exhaust-gas mass lower fuel-consumption figures. This has the running-up characteristic. flat spot. Today. Systems based on internal A/F. motive sector. since they have fuel mass is not defined by the injector but proved to be particularly suitable in the by the system’s fuel distributor. particularly when formed outside the combustion chamber. the mixture is Fuel-injection systems. in the intake manifold. only the electronically from the point of view of fuel consumption. every completely superseded by electronic fuel cylinder is allocated its own injector which injection. Development superior to carburetors in complying with of such systems was forced ahead to enable the tight limits imposed on A/F-mixture them to comply with increasingly severe composition. 1 5 Figure 1 1 Fuel æ UMK0662-2Y 2 Air 3 Throttle valve 4 Intake manifold 5 Injector 6 6 Engine . never-ending endeavours to reduce fuel con- sumption. sprays the fuel directly onto the cylinder’s intake valve (Fig. 1). controlled multipoint injection systems are driveability. Multipoint fuel-injection systems tion have led to the carburetor being On a multipoint injection system. or Overview carburetor. of any importance in this sector. and power output. that is with the fuel in. this system features electroni- 2 cally controlled supplementary functions 3 which permit the injected fuel quantity to be even more accurately adapted to changing 4 engine operating conditions. on the majority of these injection are ideal for complying with the demands systems the A/F mixture is formed externally made on the A/F-mixture formation system. On gasoline injection systems with external A/F-mixture formation. Mechanical fuel-injection system mixture formation. they are better demands. Robert Bosch GmbH 34 Gasoline fuel injection: An overview Gasoline fuel injection: An overview It is the job of the fuel-injection system. they are electronically controlled. outside the combustion chamber (manifold injection). The injected to the forefront though. In the auto. to meter to the engine the best- possible air/fuel mixture for the actual External A/F-mixture formation operating conditions. The K-Jetronic injection system operates jected directly into the cylinder (gasoline di. rect injection). are far that is. In addition. without any form of drive from the engine. Such injection systems At present. are coming more and more and injects fuel continuously. Combined mechanical-electronic fuel- injection system The KE-Jetronic is based on the basic mechanical system used for the K-Jetronic. 1 Multipoint fuel-injection system Thanks to additional operational-data acquisition. the demands imposed by increasingly severe emission-control legisla. 3). This injection system intermittently for. 2 Single-point injection (TBI) system 3 Direct-injection (DI) system 2 2 Figure 2 1 5 1 Fuel 3 2 Air 3 Throttle valve 3 4 4 Intake manifold 5 Injector 6 Engine 4 1 5 Figure 3 1 Fuel 2 Air æ UMK0663-2Y æ UMK1687-3Y 3 Throttle valve (ETC) 4 Intake manifold 5 Injectors 6 6 6 Engine . The remainder of the combustion Motronic. This operating mode is therefore a central point directly above the throttle applied when high levels of torque are called valve. similar to external A/F-mixture formation. The injected fuel quantity is defined by of which has been allocated to each cylinder the injector opening time (for a given (Fig. one tors. 2). ber. other hand. pressure drop across the injector). chamber only contains fresh gas and resid- ual gas without any unburnt-fuel content. This results in an extremely lean mixture at idle and part-load. ber through electromagnetic injectors. chamber participates in the combustion tromagnetically operated injector located at process. with a corresponding drop in fuel consumption. plug. and A/F-mixture formation inside the com- Motronic in the form of an integrated bustion chamber permits two completely engine-management system (M and different operating modes: In homogeneous ME-Motronic). LH-Jetronic. it is only necessary to have an The Bosch single-point injection systems are ignitable A/F mixture around the spark designated Mono-Jetronic and Mono. In stratified-charge operation on the injects fuel into the intake manifold (Fig. Robert Bosch GmbH Gasoline fuel injection: An overview 35 Electronic fuel-injection systems Internal A/F-mixture formation Electronically controlled fuel-injection On direct-injection (DI) systems. The MED-Motronic is used for the man- agement of gasoline direct-injection en- gines. and all the fresh air in the combustion tle-body injection or TBI) features an elec. operation. Examples: L-Jetronic. A/F-mixture formation takes place inside the combustion chamber. the fuel is systems inject the fuel intermittently injected directly into the combustion cham- through electromagnetically operated injec. a homogeneous A/F mixture is Single-point injection present throughout the combustion cham- Single-point injection (also known as throt. nents are mainly concerned with the supply of fuel as defined above (Fig. the electric fuel pump comes into operation immediately the Overview ignition/starting switch is turned. the fuel system when the fuel heats up after gines. the fuel pump delivers more fuel which are involved in the supply of fuel than is actually required by the engine. tank. or ter to the engine. defined pressure. So that the required fuel pressure is available for starting the engine. The fuel-pressure regula- directly into the combustion chamber tor maintains a defined pressure in the fuel (direct injection). pre- liminary filter. depending on the type of fuel-injec- must be supplied to the injectors at a tion system. the fuel pump is inside the fuel tank (“in-tank” pump). the electric fuel pump is located outside the fuel tank in the fuel line itself (so-called “in-line” pump). the fuel circuit. the following compo.g. Robert Bosch GmbH 36 Fuel supply An overview Fuel supply The injectors (injection valves) of a gasoline The electric fuel pump delivers fuel continu- injection system inject the fuel into the ously from the fuel tank and through the fil- intake manifold (manifold injection). The fuel
Electric fuel pump (2). case of gasoline direct injection. about 1 second. it stops again after Basically speaking. On more recent systems. the engine has been switched off. 1): To a great extent. Ex- from the fuel tank to the injectors or. . from the fuel tank to the high-pressure pump. On gasoline direct-injection en. sure circuit by the high-pressure pump. After the fuel pump has been switched off. the fuel pump system pressure for a certain period. and tank by preventing fuel returning to the
Fuel lines (6 and 7). It can also be combined with other components (e. the fuel is forced into the high-pres. system is provided with an integral non-re-
Fuel filter (3). in the cess fuel is returned to the tank. turn valve which decouples it from the fuel
Fuel-pressure regulator (4). In both cases. fuel-level sensor) in the tank in an in-tank unit. On older systems. If the engine is not started. the pressure generated by the fuel pump serves to prevent the forma-
Fuel tank (1). In order that the required fuel pressure can be maintained under all operating con- This chapter describes the components ditions. This forces the fuel to the injector (8) via the fuel prevents the formation of vapor bubbles in rail (5). the non-return valve maintains the With manifold injection. tion of vapor bubbles in the fuel. there are two systems for fuel supply sure and therefore also of cylinder charge. Versions There are a variety of different versions of Fuel-supply system with fuel return the fuel-supply system with return. injection It is independent of intake-manifold pres- Here. 8). 0.3 MPa (3 bar). The Excess fuel is that fuel which the injector standard version with fuel flowing through does not inject (Fig 1. There are also page. Robert Bosch GmbH Fuel supply Fuel supply for manifold injection 37 Fuel supply for manifold This has the advantage that the injected fuel quantity is a function of the injection time. 2a. 8 and Fig. Pos. so that there is The intake-manifold pressure is applied as no direct flow through the rail. Since the fuel-pressure regulator is situated System pressure very close to the manifold. Pos. it is possible here On present-day systems with fuel return. Using this reference pres- sure results in a constant difference between the fuel-system pressure and the intake- manifold pressure. 4 Fuel-pressure æ UMK1702-1Y regulator 5 Fuel rail 6 Fuel line 1 2 7 Fuel-return line 8 Injector . which differ according to the type of fuel re- turn. It is returned to the fuel tank versions on the market in which the fuel line (1) via the fuel-pressure regulator (4) which (6) in connected to the same end of the rail is usually located on the fuel rail (5). next the rail is shown in Fig. as the fuel-pressure regulator. the reference for system-pressure control. the to locate the reference connection directly system pressure is approx. 1 Fuel supply system for a manifold-injection engine (version with fuel return) 4 5 7 8 6 3 Figure 1 1 Fuel tank 2 Electric fuel pump (here integrated in the fuel tank). on the manifold. 3 Fuel filter. 2. sure regulator therefore regulates the system partment.. The
Fuel filter and pressure regulator both excess fuel delivered by the pump is re. and secondly the fact that the provide an manifold reference connection at fuel in the tank does not heat up since no the fuel-pressure regulator. the fuel tank. On returnless fuel systems the pressure is approx. integrated in the in-tank unit (fuel-supply turned directly to the tank via a short return module)... to the fuel tank can be dispensed with. line from the pressure regulator.5.4 MPa (3. Pos. tity is a function of the manifold pressure. and therefore referred to the surrounding/ambient pres- to reduced loading of the evaporative-emis. Robert Bosch GmbH 38 Fuel supply Fuel supply for manifold injection 2 Fuel-supply system for a manifold-injection engine (examples) b 5 a Figure 2 a With fuel return 6 4a 5 b Without fuel return 6 8 1 Fuel tank 2 Electric fuel pump 3 7 8 3 Fuel filter 4a Fuel-pressure regulator (intake. The fuel-pres- hot fuel is returned from the engine com. the fuel-return line from the fuel rail side the fuel tank.4 bar). 4b lator (surrounding 2 pressure used as 2 æ UMK1252-1Y reference) 5 Fuel rail 6 Fuel line 7 Fuel-return line 8 Injectors Returnless Fuel System Versions The fuel-pressure regulator (Fig. nent part of the in-tank unit. It can also be installed as a compo.. This fact is taken into account when calcu- lating the injection duration.
Fuel filter outside. sure. This means that the injected fuel quan- sions control system. . 0. pressure regulator in- tems. System pressure livered to the fuel rail. This leads to a reduction in the pressure to a constant pressure differential HC emissions at the fuel tank. Since it would be too far away from the in- This system has two advantages: Firstly take manifold it is practically impossible to lower costs. 4b) There are a number of different returnless for the Returnless Fuel System (RLFS) is fuel systems available: usually installed inside the fuel tank or in its
Fuel filter and pressure regulator outside vicinity. Only the fuel actually injected by the injectors is de. 3 7 manifold pressure 1 used as reference) 1 4b Fuel-pressure regu. 2b.0.35. On such sys. tween two different levels. the low-pressure circuits for nents against excess pressure. pump has been thoroughly flushed and cooled off far enough so that there is no Example of an installation longer any danger of vapor-bubble forma- Fig.3 MPa (3 bar). functions. the bubbles in the high-pressure pump (7) dur- fuel-supply system can be divided into the ing the starting phase and the subsequent hot-idle phase.. the high-pressure
Without fuel return (RLFS). and After 30. and sure is a suitable step. mary pressure to 0. This is a fuel system with return. the pressure in the low-pressure (pri. When located in the fuel tank. pressure to 0. the pres- Depending upon the vehicle manufacturer’s sure limiter not only protects the compo- requirements. measures must be gasoline direct injection taken to prevent the formation of vapor On the gasoline direct-injection system. Increasing the primary pres-
Low-pressure circuit.. Here. The shutoff valve opens.60 seconds. In this case. control function and adjusts the primary mary pressure) circuit can be switched be. Figure 1 Low-pressure (primary) circuit with 1 Fuel supply for a gasoline direct-injection system (example with fuel return and primary-pressure changeover) 1 Fuel tank 2 Electric fuel pump 11 with integral pres- 7 8 10 sure limiter and fuel filter 3 Shutoff valve 9 4 Pressure regulator 5 Fuel line 5 3 6 Fuel return line High-pressure circuit 4 6 with 7 High-pressure pump 8 Rail 1 9 High-pressure injectors æ UMK1775Y 10 Pressure-control 2 valve 11 Fuel-pressure sensor . sumes responsibility for pressure-control ably in design. the pressure regulator is lo- cated in the engine compartment.5 MPa (5 bar). the shutoff valve
High-pressure circuit. and the pres- return and primary-pressure changeover. Similar to the manifold injec. sure regulator (4) takes over the pressure- Here. there are also variants here Lower primary pressure
With fuel return. but also as- such injection systems can differ consider. (3) remains closed so that the pressure lim- iter integrated in the electric fuel pump (2) The high-pressure circuit is described in the comes into operation and adjusts the pri- Chapter “Gasoline Direct Injection”. 1 shows a fuel system featuring both fuel tion. tion system. Robert Bosch GmbH Fuel supply Low-pressure circuit for gasoline direct injection 39 Low-pressure circuit for Higher primary pressure When the fuel is hot.  In-tank unit: The complete unit for a returnless fuel system (RLFS) 4 5 1 2 1 Fuel filter 2 Electric fuel pump 3 6 3 Jet pump (closed- æ UMK1439-1Y loop controlled) 4 Fuel-pressure regulator 5 Fuel-level sensor 6 Preliminary filter . on the other hand. ply module. always installed in the fuel line (“in-line”) out. as the name implies. and  A special fuel reservoir for maintaining the fuel supply when cornering or in sharp bends. the electric fuel pump was electric fuel pump keep this reservoir full. Robert Bosch GmbH 40 Fuel supply Integration in the vehicle: In-tank unit
Integration in the vehicle: In-tank unit In the early years of electronically controlled Usually. a jet pump or a separate stage in the gasoline injection. The “in-tank” type and. are pressure-side fine fuel filter can also be lo- part of an “in-tank unit”.  Electric and hydraulic connections. lator (4). cated in the in-tank unit. This contains an increasing num- ber of other components. the fuel-pressure regu- side the fuel tank. module for triggering the electric fuel pump. the fuel-supply module will incorpo- rate further functions. devices for detecting tank leaks. Today. or the timing  A fuel-level sensor. is usually integrated in the in-tank unit the majority of electric fuel pumps are of the where it is responsible for the fuel return. On RLFS systems. for instance diagnosis  A preliminary filter. the so-called fuel-sup. for instance: In future. instance when driving up a hill in the For instance. As soon as the canister- purge valve opens the line (6) between the 1 carbon canister and the intake manifold. The activated carbon in the carbon canis. the activated carbon must be regener- sions control systems. together with the so-called canister-purge valve (5) which is connected to both the carbon canister and the intake manifold (8). fuel vapor escaping to the atmosphere from the fuel tank. In order to ensure that the car- evaporative hydrocarbon emissions. the engine must be Design and operating concept operated in the homogeneous mode until The evaporative-emissions control system the high concentrations of gasoline in the (Fig. if the canister-purge gas flow is mountains. uum in the intake manifold (caused by prac- due either to high surrrounding tempera. por. the fuel tank (1). for compared to homogeneous operation. Robert Bosch GmbH Fuel supply Evaporative-emissions control system 41 Evaporative-emissions The canister-purge gas quantity is controlled as a function of the working point and can control system be very finely metered using the canister- In order to comply with the legal limits for purge valve. The system control reduces the in. The ab. 2 sorbed fuel is then entrained with the fresh Figure 1 5 air (purging or regeneration of the activated 1 Fuel tank carbon) and burnt in the normal combustion 2 Fuel-tank venting 7 3 process. 1) comprises the carbon canister (3). inadequate for coping with high levels of gasoline evaporation. This system prevents ated at regular intervals. This compartment. the vacuum in the manifold causes fresh air to be 6 drawn through the activated carbon. vehicles bon canister is always able to absorb fuel va- are being equipped with evaporative-emis. the possibility under the following circumstances: of regenerating the carbon canister’s con- tents is limited due to the low level of vac-
When the fuel in the fuel tank warms up. tically 100 % “unthrottled” operation) and tures. Regeneration is 4 Fresh air æ UMK1706-1Y 5 Canister-purge valve a closed-loop control process. line jected fuel quantity by the amount returned 3 Carbon canister through canister-purge valve. or to the return to tank of excess the incomplete combustion of the homoge- fuel which has heated up in the engine neously distributed canister-purge gas. 8 Intake manifold . and results in reduced canister-purge gas flow
When the surrounding pressure drops. Gasoline direction injection: Special features Fuel-vapor generation During stratified-charge operation on gaso- More fuel vapor escapes from the fuel tank line direct-injection engines. canister-purge gas flow have dropped far into which is led the venting line (2) from enough. 1 Evaporative-emissions control system ter absorbs the fuel contained in the fuel va- por and thus permits only air to escape into the atmosphere. whereby the 8 6 6 Line to the intake fuel concentration in the canister-purge gas 4 manifold flow is continuously calculated based on the 7 Throttle valve changes it causes in the excess-air factor λ. at rated voltage. low as between 50 and 60 % of rated volt. Pressure pulsations. the EKP is increasingly be. Efficiency can be as high as 25 %. Figure 1 5 Whereas in electronic gasoline-injection sys- 1 Electric connections tems the positive-displacement pump has to B 2 Hydraulic connec. For the EKP. 1. A).. delivery-rate characteristic as a function of erations.5 bar). 2a. gear pumps or roller-cell pumps (Figs. The most important performance
Pump element (C). These feature a good low-voltage char- instance.
Pressure in the fuel system between 300 Types and 450 kPa (3. it has captured a new field of 4 Carbon brushes application as the presupply pump on 5 Permanent-magnet direct-injection systems wihich operate with æ UMK1280-3Y motor armature 6 C far higher fuel-pressures. Positive-displacement pumps
System-pressure buildup even down to as In this type of pump. positive- diesel and gasoline engines. the fuel is drawn in. can cause audible noise depending 1 Electric fuel pump: Design and construction upon the particular design details and in- using a turbine pump as an example stallation conditions. and for A this reason conventional positive-displace- 4 ment pumps are equipped with peripheral preliminary stages for degassing purposes. that is. they have a relatively flat sometimes required during hot-delivery op. incorporating spark- times deliver enough fuel to the engine at a suppression elements if required. compressed in a closed chamber by rotation age. a great extent been superseded by the tur- tions (fuel outlet) bine pump for the classical fuel-pump 3 Non-return valve requirements. and transported to the high-pressure side. see Section “Types”
Delivery quantity between 60 and 200 l/h below). which are unavoid- able. The fact that the deliv- ery rate can drop when the fuel is hot is 1 another disadvantage which can occur in 2 exceptional cases. 6 Turbine-pump impeller ring 7 Hydraulic connec. high enough pressure to permit efficient fuel
Electric motor (B). Robert Bosch GmbH 42 Fuel supply Electric fuel pump Electric fuel pump Design and construction The electric fuel pump is comprised of: Assignment The electric fuel pump (EKP) must at all
End plate (Fig. the operating voltage.4. of the pump element. designed as either demands made on the pump are: positive-displacement or turbine pump (for description. displacement pumps are particularly suit- On gasoline direct-injection systems for able. pressures of up to 700 kPa are acteristic. 7 tion (fuel inlet) . This is due to vapor bub- 3 bles being pumped instead of fuel. internal- Apart from this. ing used as the pre-supply pump for the 2b) are used. and injection. When high system pressures modern direct-injection systems used on are needed (400 kPa and above).. of the positive-displacement pumps. The degassing bore is not B B a Roller-cell pump needed with diesel applications. the 6 Impeller-ring blades two channels are located on each side of the 7 Passage impeller ring adjacent to the blades. Effi. clusively on newly designed gasoline-engine Construction though is far simpler than that automobiles. Robert Bosch GmbH Fuel supply Electric fuel pump 43 Turbine pumps 2 Principle of functioning of electric fuel pumps This type of pump comprises an impeller ring with numerous blades inserted in slots a 1 2 around its periphery (Fig. The “Stopper” between start and end of the passage pre- vents internal leakage. 6). A This. The impeller ring with blades rotates in a cham. For costs reasons. is at the cost of very slight in. This A Intake port leads to spiral-shaped rotation of the liquid B B Outlet volume trapped in the impeller ring and in 1 Slotted rotor the passages. B æ UMK0267-3Y A 5 Impeller ring ripheral”). b 3 4 take opening a small degassing bore has been provided which provides for the exit of A any gas bubbles which may be in the fuel. Figure 2 ternal leakage. each of which has a passage (7) adjacent to the blades which starts at the level of the in- take port (A) and terminates where the fuel B is forced out of the pump at system pressure B through the fuel outlet (B). . turbine pumps will also be suitable for the higher system pressures that will be needed for brief periods on highly supercharged en- gines and gasoline direct-injection engines. Single-stage pumps can generate system pressures of up to 450 kPa. At a given angle and distance from the in. although improving the hot-delivery characteristics. (peripheral) 8 “Stopper” Turbine pumps feature a low noise level since pressure buildup takes place continu. (RZP) b Inner-gear pump Pressure builds up along the passage (7) as a (IZP) result of the exchange of pulses between the c Peripheral pump c 8 5 6 7 7 5 7 6 (PP) ring blades and the liquid particles. In future. In the case of the peripheral (eccentric) A pump (Fig. quieter. Pos. and due to their being ously and is practically pulsation-free. On the side-channel pump. turbine pumps are used almost ex- ciency is between 10 % and about 20 %. 3 Inner drive wheel 4 Rotor pletely by the passage (hence the word “pe. 2c). A A ber formed from two fixed housing sections. the ring blades around the 2 Roller periphery of the ring are surrounded com. 2c. diffusion. Filter housings (2) are either steel. 3). 10 µm. Guaranteed mileages of 100.000 miles (250. Filters in the fuel circuit impregnated.000 km). plastic. or are integrated in the fuel that the velocity of the fuel flow through all tank as “lifetime” in-tank filters.000. 4 Filter efficiency depends on the throughflow direction. when a new filter is fitted the traces of cont- aminant remaining in the filter after manu- facture are an important factor: Metal. or plastic (100 % free from metal). alu- 3 minum. Depending upon the filter volume. it is imperative that the fuel is Pleated paper.500 and 55. and the ignition (SI) engines operate with extreme filter medium is matched to these factors. far finer filtering is needed for gaso- and blocking effects. speed of the contaminant particles. for gasoline direct injection. The filter wear. When replacing in-line filters. 1 Section through a fuel filter In addition. There are in-tank and in-line filters available for 2 use with gasoline direct-injection systems which feature service lives in excess of 150. or quick- connect type are used. and glass-fiber particles must not exceed 200 µm. which is sometimes specially efficiently cleaned. Pos. Such filters are either replaceable medium is arranged in the fuel circuit so in-line filters. Connections of the threaded.90. 1. the use- 1 ful life (guaranteed mileage) of the conven- tional in-line filter is somewhere between 37.. a number of different processes are applied Whereas on manifold-injection systems in order to remove the contaminants from the filter element has a mean pore size of the fuel. precision. ble.000 miles (60. Apart from sections of its surface is as uniform as possi- the filter’s purely straining or filtering effect. min- eral. Robert Bosch GmbH 44 Fuel supply Fuel filter Fuel filter The filtration efficiency of the individual ef- fects is a function of the size and the flow The injection systems for automobile spark. 1 Filter cover æ UMK1779Y 2 Filter housing 3 Filter element 4 Support plate . These include impact.. has come to the forefront as remove the solid particles which could cause the filter medium (Fig.000 km). it is imperative that the flow direction given by Figure 1 the arrow is observed.000 km) apply for in-tank filters. line direct-injection systems where up to 85 % of the particles larger than 5 µm must be reliably filtered out of the fuel. hose.000 miles (160. In order not to damage their pre- cision parts. the stainless-steel fuel rails are used. the spring (2) injection period and the difference between forces a movable valve plate against the valve the fuel pressure in the fuel rail and the seat so that the valve closes. back to the fuel tank that equilibrium of tween fuel pressure and manifold pressure at forces is achieved again at the diaphragm. and stant and must be taken into account when is an integral part of the high-pressure stage. The fuel rail pressure regulator is part of the in-tank unit can incorporate a diagnosis valve for work.
Storage of the fuel volume. Local nection 2 Spring fuel-pressure fluctuations caused by reso- 3 Valve holder æ UMK1781Y nance when the injectors open and closed. 7 6 Fuel inlet jected fuel quantity which can arise as a 7 Fuel return function of load and engine speed are avoided. 1) is of the Fuel-pressure regulator diaphragm-controlled overflow type. the valve opens sure is compensated for by a pressure regu. Through a valve holder (3) (injected fuel quantity) depends upon the integrated in the diaphragm. This Gasoline direct injection means that the difference between fuel-rail On gasoline DI systems. fuel-pressure regulator 45 Fuel rail 1 Fuel-pressure regulator DR2 Manifold injection The fuel rail has the following assignments: 1
Mounting and location of the injectors. sure regulator is normally located at the end Depending upon the particular require. irregularities in in. the injection duration is calculated. In order to ensure that the fuel rail is efficiently flushed. fuel exceeds the spring force. is 4 Diaphragm 6 6 prevented by careful selection of the fuel-rail 5 Valve dimensions. the rail is located pressure and manifold pressure is not con- downstream of the high-pressure pump. 3 4 In addition to the injectors. Robert Bosch GmbH Fuel supply Fuel rail. A rub- ber-fabric diaphragm (4) divides the pres- Manifold injection sure regulator into a fuel chamber and a The amount of fuel injected by the injector spring chamber. As soon as the counterpressure in the manifold. As a result. The fuel-rail pres- shop testing purposes. installed in the fuel tank. again and permits just enough fuel to flow lator which maintains the difference be. the influence of pres. Figure 1 ally accomodates the fuel-pressure regulator 5 1 Intake-manifold con- and possibly even a pressure damper. sure is maintained at a constant level with reference to the surrounding pressure. 2
Ensuring that fuel is distributed evenly to all injectors. of the rail which leads the fuel tank. The fuel-pressure regulator (Fig. the fuel rail usu. On fuel pressure applied to the diaphragm by the systems with return. the fuel-pres- . This pressure regulator per- mits just enough fuel to return to the tank so that the pressure drop across the injectors remains constant. ments of the vehicle in question. a constant level. plastic or On returnless fuel systems (RLFS). together with the periodic supply of of escaping fuel in case of an accident. As its name implies. fuel tank. with correct performance. Robert Bosch GmbH 46 Fuel supply Fuel-pressure damper. and lines. The fuel tank must be situated The repeated opening and closing of the in. fuel so that mechanical damage is avoided. not be used in the fuel-supply circuit. in or. it is corroding and must remain free of leaks at necessary to regulate the pressures in the up to twice working pressure. the spring cham- der that the manifold vacuum can be ap. Fuel lines lations. aphragm separates the fuel chamber from the air chamber. nected pneumatically to the intake manifold Similar to the fuel-pressure regulator. fuel which has evaporated or dripped as a These problems are alleviated by the use result of malfunctions cannot accumulate or of special-design mounting elements and ignite. manifold injection. on inclines. Gravity feed must sure regulator. In the diaphragm as at the injectors. no fuel may leak out Fuel-pressure damper through the filler cap or pressure-compensa- tion devices. fuel when electric positive-displacement fuel pumps are used. also be attached to the high-pressure pump. leads to fuel-pressure oscil. It must be non- On gasoline direct-injection systems. The spring force is selected such that the diaphragm lifts from its seat as soon as the fuel pressure reaches its working range.The fuel-pressure be protected against heat that could interfere damper is similar in design to the fuel-pres. jectors is solely a function of spring force and diaphragm surface area.3 bar) gauge pressure. and in case of shock or impact. ber can be provided with an intake-manifold plied to the spring chamber. whereby the same fuel-pressure regulators Openings or safety valves must be provided are used for the low-pressure stage as for for excess pressure to escape automatically. circumstances. but also releases fuel when the pressure drops. fuel lines On multipoint fuel-injection systems. It is even possible that under certain the fuel tank to the fuel-injection system. This the case of gasoline direct injection. connection. or up to at high-pressure and the low-pressure stage. it can means that the pressure drop across the in. this is con. and fuel pump. These can cause pressure resonances which adversely affect fuel-metering accu. a spring-loaded di. conditions at the manifold. least 0. the fuel tank is used as Gasoline direct injection the reservoir for the fuel.03 MPa (0. During cornering. and therefore Fuel tank remains constant. In order to always operate in the most favorable range when the absolute fuel pressure fluctuates due to . flexible metal conduit or fuel-re- oscillations being transferred to the fuel tank sistant hardly combustible material can be and the vehicle bodywork through the used for the fuel lines. All fuel-carrying components must fuel-pressure dampers. fuel-pressure damper can also be attached to There is therefore the same pressure ratio at the fuel rail or installed in the fuel line. the at a point downstream of the throttle plate. far enough from the engine to avoid ignition jectors. The fuel lines serve to carry the fuel from racy. This means that the fuel chamber is variable and not only absorbs fuel when pressure peaks occur. noise can be caused by these Seamless. These must be routed mounting elements of the fuel rail. Here too. Robert Bosch GmbH Fuel supply Fuel-supply systems 47 1 Development of fuel-supply systems (examples) a K-/KE-Jetronic 4a 6 with electric (in-line) fuel pump. Figure 1 1 Fuel tank 2 Electric fuel pump (EKP) 3 3 Fuel filter 4 Fuel rail 1 4a Fuel distributor (K-/KE-Jetronic) 5 Injector æ UMK1780E 2 6 Pressure regulator 7 Fuel accumulator (K-/KE-Jetronic) . 3 1 5 7 2 b L-Jetronic/Motronic 6 4 with electric (in-line) fuel pump. 3 5 1 2 c L-Jetronic/Motronic 6 4 with electric (in-tank) fuel pump. 3 5 1 2 d Mono-Jetronic 5 6 with electric (in-tank) fuel pump. Since they were ulations are being increasingly tightened so introduced to the market. This system injects the fuel intermittently. improved. it is also imperative that injection of the fuel takes place at exactly the right instant in time. which also operates with external A/F-mix. and individually. nor do the single-point (TBI) systems the latest state-of-the-art. these engines and that fuel-injection system development is their control systems have been vastly forced to keep pace. of the throttle valve. these technical stip- the combustion chamber. the elec- characteristics have enabled them to com. injector into the intake manifold upstream tion of the A/F mixture. tronically controlled multipoint fuel-injec- pletely supersede the carburetor engine tion system represents the state-of-the-art. for each cylinder directly onto its intake valve(s) (Fig. Their superior fuel-metering In the manifold-injection field. 1). Robert Bosch GmbH 48 Manifold fuel injection Overview Manifold fuel injection Manifold-injection engines generate the A/F As a direct result of increasingly severe emis- mixture in the intake manifold and not in sion-control legislation. Overview Mechanically controlled continuous-injec- Regarding smooth running and exhaust-gas tion multipoint systems no longer have any behaviour very high demands are made on significance for new developments in this modern-day vehicles which correspond to field. 1 Manifold injection 3 5 2 Figure 1 4 1 Cylinder with piston 6 2 Exhaust valves 3 Ignition coil with æ UMK1776Y spark plug 4 Intake valves 5 Injector 1 6 Intake manifold . cision metering of the injected fuel mass as a function of the air drawn in by the engine. Apart from the pre. ture formation. This leads to strict which inject intermittently through a single requirements with respect to the composi. The ECU then applies the allocated its own injector which injects in. data on intake air mass and the engine’s in- termittently into the intake manifold di. see “External points. As an al- ternative. this data is then used to calculate the jection at system pressure. Robert Bosch GmbH Manifold fuel injection Operating concept 49 Operating concept Provided the A/F mixture is stoichiometric Gasoline injection systems of the manifold. At the majority of their operating the intake manifold (Fig. or even three. manifold-injection engines are there- A/F-mixture formation”. be measured exactly. Since the injector is situated directly opposite the intake valve. finely atomized fuel evaporates to a great extent. and together with the intake air en. it is imperative that the mass stroke. two. the pollutants generated during the injection type are characterized by the fact combustion process can to a great extent be that they generate the A/F mixture outside removed using the three-way catalytic con- the combustion chamber. the fuel mass in the wall film must be kept to a minimum. . in other words. in verter. Together with The electric fuel pump delivers the fuel to the throttle-valve setting and the engine the injectors where it is then available for in. electric signal to the engine ECU. therefore. This is achieved by appropriate manifold design and fuel-spray geometry. In order that enough time is avail. For good dynamic engine response. and is a func- the fuel is best sprayed onto the closed tion of the injector’s opening cross section intake valve and “stored” there. speed. stantaneous operating mode to calculate the rectly onto the intake valve (6). (4) where together with the intake air it forms the A/F mixture which is then drawn Measuring the air mass into the cylinder (1) past the open intake In order that the A/F mixture can be pre- valves during the subsequent induction cisely adjusted. Each cylinder is intake-air mass. The thickness of the film is a func- tion of the manifold pressure and. 1). Injection duration tering via the throttle plate generates the A/F A given length of time is needed for the in- mixture. and the difference between the intake-mani- fold pressure and the pressure prevailing in Some of the fuel is deposited as a film on the the fuel-supply system. there are also systems on the mar- A/F-mixture formation ket which use a pressure sensor to measure Fuel injection the intake-manifold pressure. the wall- film effects with multipoint injection systems are far less serious than they were with the former TBI and carburetor systems. termed the injection duration. The injector (5) fore operated with this A/F mixture compo- sprays the fuel directly onto the intake valves sition. It engine’s fuel requirements are covered irre. This is able for the generation of the A/F mixture. Here the required fuel mass. of engine load. jection of the calculated fuel mass. (λ = 1). The air-mass meter is The intake valves are designed so that the situated upstream of the throttle valve. One. manifold walls in the vicinity of the intake valves. measures the air-mass flow entering the in- spective of operating conditions – at full take manifold and sends a corresponding load and at high engine revs. intake valves of the air which is used for combustion can can be used per cylinder. The seal ring (2) on the
The geometry of the fuel-exit area. The injector is inserted into the opening tion by a filter strainer (3) at the fuel input. fuel supply tially. from top to bottom (“top feed”). that time is determined by is. The spray pattern of fice plate (7). This has led to a variety of different injector designs. the precise metering of the quantity of fuel As soon as the solenoid is energised (excita- required by the engine. valve seat is due to the cone/ball sealing jector which come into contact with fuel. provided for it in the intake manifold. principle. the valve needle Essentially. Types of construction The injector is connected electrically to In the course of time. Robert Bosch GmbH 50 Manifold fuel injection Electromagnetic fuel injectors Electromagnetic fuel Injector operation With no voltage across the solenoid (sol- injectors enoid de-energised). and the the fuel leaving the injector is a function of
Spring (5). ment and fastening. The fuel
The fuel-supply system pressure. These holes (spray orifices) are
The coil for the electromagnet (4). As soon as the excitation Design and operating concept current is switched off. The fuel-supply manifold at system pressure. lated by the engine-management system. the injected fuel quantity per unit of to the injector is in the axial direction. hydraulic connection (1) seals off the injec- tor at the fuel rail. In order to ensure trouble-free operation. injected fuel quantity remains highly repro- enoid armature and sealing ball. line is fastened to the injector using a special
The counterpressure in the intake mani- clamp. stamped out of the plate and ensure that the
The movable valve needle (6) with sol. the electromagnetic injectors closes again due to spring force. and weight. the number of orifices and their configura- tion. They permit system is thus sealed off from the manifold. They are triggered tion current). Essen- On the injectors presently in use. this generates a magnetic field via ECU driver stages with the signal calcu. reliability. which pulls in the valve-needle armature. The sealing ball lifts off the valve seat and the fuel is injected. The highly efficient injector sealing at the stainless steel is used for the parts of the in. further and further developed to match them to the ever-increasing demands re- garding engineering. fold. (Fig. ber of holes. Retaining clips ensure reliable align. . ducible. The bottom seal ring provides the seal between Connections the injector and the intake manifold. the valve needle and Assignment sealing ball are pressed against the cone- The electromagnetic (solenoid-controlled) shaped valve seat by the spring and the force fuel injectors spray the fuel into the intake exerted by the fuel pressure. sitive to fuel deposits. the injectors have been the engine ECU. The injector is protected against contamina. quality. 1) are comprised of the following com- ponents: Fuel outlet The fuel is atomized by means of an injec-
The injector housing (9) with electrical tion-orifice plate in which there are a num- (8) and hydraulic (1) connections. The injection-orifice plate is insen-
The valve seat (10) with the injection-ori. ful life. Robert Bosch GmbH Manifold fuel injection Electromagnetic fuel injectors 51 EV6 injector ments for even better fuel atomization. It main highly reproducible over long periods is even more compact. tates its integration in the fuel rail. no fuel engine’s intake-manifold geometry. Thanks to wear-resisting surfaces. that is. This injector therefore already pro. lengths (compact. feature different lengths. That is. These with regard to its hot-fuel behaviour. suitable for use with fuels having an ethanol tates the use of RLFS fuel-supply systems in content of as much as 85 %. The EV6 injector is the standard injector for Finely vaporized fuel can be generated using today’s modern fuel-injection systems other methods: In future. The EV6 variant with “air shrouding” was developed especially to comply with require- 1 Design of the EV6 electromagnetic injector 2 Injector versions 1 b Figure 1 2 1 Hydraulic connec- 3 8 tion 2 Seal rings (O-rings) a 3 Filter strainer 4 Coil 4 9 5 Spring 5 6 Valve needle with armature and sealing ball 7 Injection-orifice plate 6 8 Electrical connec- 10 tion 9 Injector housing æ UMK1712-3Y 2 10 Valve seat æ UMK1786Y 7 Figure 2 a EV6 Standard b EV14 Compact . 2b) which is based on the EV6. There are a wide variety of injectors avail- In addition. It is characterized by its 4-hole injection-orifice plates. vapor escapes from them. Further injector development has led to the the fuel quantities injected by the EV6 re. used. a fact which facili- of time. and there is very little tendency for vapor-bubble electrical characteristics. 1 and 2a). This facili. Injectors equipped with these multi- vides one of the prerequisites for the design orifice plates generate a very fine fuel fog. and the injector features a long use. flow classes. the EV6 is also outstanding able for different areas of application. This these injectors fulfill all future requirements makes it possible to adapt individually to the regarding zero evaporation. standard. EV14 (Fig. which the fuel temperature in the injector is higher than with systems featuring fuel EV14 injector return. long). The EV14 is available in 3 different Thanks to their highly efficient sealing. of compact intake modules. in addition to (Figs. The EV6 is also formation when using hot fuel. multi-orifice small external dimensions and its low plates with between 10 and 12 holes will be weight. ture. a b Tapered spray further parameter which is important for c Dual spray optimisation of the fuel-consumption and d Spray offset angle c d exhaust-gas figures is the instant of injection α80: 80 % of the injected referred to the crankshaft angle. cylinder must be equipped with dual-spray cally eliminates the wetting of the manifold injectors. its A number of individual jets of fuel leave the fuel-spray shape. Each of these sprays can be The pencil-spray injector is only used in formed from a number of individual sprays isolated cases due to its low level of fuel (2 tapered sprays). that is. atomization. The spray offset angle Referred to the injector’s principle axis. cylinder. concentrated. Dual spray “Pencil” spray The dual-spray formation principle is often A thin. types of fuel injection Spray formation Tapered spray The injector’s spray formation. have a considerable influ. fuel jets. 3 shows the with 2 intake valves per cylinder. the fuel is within the possible variations are dependent upon the angle defined by α type of injection actually used (Fig. This form of spray practi. Here. Different versions of spray formation Although engines with only 1 intake valve are required in order to comply with the per cylinder typically use tapered-spray demands of individual intake-manifold and injectors. Such injectors are most suitable for use The holes in the injection-orifice plate are with narrow intake manifolds. fuel in a single spray is within the angle defined by β α50 γ: Spray offset angle . wall. the spray offset angle a b (γ). 1). and in instal. and highly-pulsed fuel applied on engines with 2 intake valves per spray results from using a single-hole injec. Injectors with this spray shape are mostly used when installation conditions are difficult. so arranged that two fuel sprays leave the lations in which the fuel has to travel long injector and impact against the respective distances between the point of injection and intake valve or against the web between the the intake valve. Fig. the 3 Fuel-spray shapes fuel spray in this case (single spray and dual spray) is at an angle. they are also suitable for engines cylinder-head geometries. and injection-orifice plate. Engines with 3 intake valves per tion-orifice plate. spray-dispersal angle. Robert Bosch GmbH 52 Manifold fuel injection Eletromagnetic fuel injectors. The tapered spray fuel-droplet size. cone results from the combination of these ence upon the generation of the A/F mix. intake valves. most important fuel-spray shapes. Types of fuel injection Figure 3 α80 α80 a Pencil spray In addition to the duration of injection. α50: 50 % of the injected The new injection systems provide for ei- fuel is within the ther sequential fuel injection or cylinder-in- angle defined by α dividual fuel injection (SEFI and CIFI re- β: 70 % of the injected β 7° æ UMK1774Y γ spectively). for instance with respect to cylinder charge. the dura- stored in front of the particular intake valve tion of injection and the start of injection but rather. the advantage that the duration of injection can be individually varied for each cylinder. Robert Bosch GmbH Manifold fuel injection Types of fuel injection 53 Simultaneous fuel injection operating point. the time available for the time which is available for fuel evaporation evaporation of fuel is different for each is different for each cylinder. 4 Cyl. pared to sequential fuel injection. 1 Manifold fuel injection: Types of fuel injection -360° 0° 360° 720° 1080° cks Firing sequence TDC cyl. and the fuel is fuel is injected into the open intake port. 1 a Simultaneous fuel Injection Cyl. Here too. 4 Cyl. This configuration enables the start of injec. and greatest degree of design freedom. the injectors being actuated one af- remainder in the next. 1 a Cyl. 1 Cyl. the fuel quantity needed for the Sequential fuel injection (SEFI) combustion is injected in two portions. the fuel for some of the cylinders is not sequence. The start of injection cannot be varied. In this form of injec. the are identical for all cylinders. Apart from this. 2 b Cyl. the un- All injectors open and close together in this desirable injection into open inlet ports is form of fuel injection. This means that the avoided. CIFI has jects. This permits compensation of irregularites. For one revolution of the crank. stored in front of each cylinder. 2 c Sequential fuel injec- tion (SEFI) and cylinder-individual fuel injection (CIFI) . Referred to piston TDC. Com- for the next revolution the second group in. 2 Figure 1 Intake valve open c Cyl. 3 injection Ignition Cyl. 1 Cyl. ter the other in the same order as the firing tion. 4 b Group fuel injection æ SMK1311-1E Cyl. Cylinder-individual fuel injection (CIFI) shaft. nevertheless obtain efficient A/F-mixture formation. one injector group injects the total This form of injection provides for the fuel quantity required for its cylinders. Start of injection is freely programmable and can be adapted to the engine’s operating Group injection state. In order to cylinder. the injectors are combined to form two groups. Half The fuel is injected individually for each in one revolution of the crankshaft and the cylinder. since the valve has opened. 3 Cyl. tion to be selected as a function of engine. 3 Cyl. Here. the “Gutbrod” was the first passenger car with a series-production me- chanical gasoline direct-injection engine. cou- pled with the requirement for reduced fuel consumption. 1 Gasoline direct injection: Components 1 2 3 4 6 5 Figure 1 8 7 1 High-pressure pump 2 Low-pressure connection 3 High-pressure line 4 Fuel rail 9 5 High-pressure injectors 6 High-pressure sensor æ UMK1783Y 7 Spark plug 8 Pressure-control valve 9 Piston . In 1952. Overview The demand for higher-power engines. These facts all contributed to it taking so long for gasoline direct injection to achieve its breakthrough. Robert Bosch GmbH 54 Gasoline direct injection: Overview Gasoline direct injection Gasoline direct-injection engines generate At that time. Moreover. The fuel is in. an engine with mechanical gasoline direct injection took to the air in an air- plane. this technology made combustion air flows past the open intake extreme demands on the materials used. During the induction stroke. designing and building a di- the A/F mixture in the combustion cham. rect-injection engine was a very complicated ber. were behind the “re-discov- ery” of gasoline direct injection. jected directly into the cylinders by special injectors. engine’s service life was a further problem. and in 1954 the “Mercedes 300 SL” followed. As far back as 1937. only the business. The valve and into the cylinder. as listed above are referred to as the engine’s terized by injecting the fuel directly into the operating modes. Depending moving the pollutants from the exhaust gas. which is opened wide. “unthrottling” also results in fuel The high-pressure injectors (5) are installed savings. The catalytic converter is responsible for re- ture in the combustion chamber. it forms the A/F mix. carbon dioxide and water by During stratified-charge operation. 1. levels of NOx emissions which are stored fied-charge A/F-mixture cloud (λ ≤ 1) is temporarily in an accumulator-type NOx formed around the spark plug (lean-burn catalytic converter. 1) at a pri. although not to the same extent as in the rail (also referred to as the “Common in stratified-charge operation.5 bar). . with the throttle tem pressure which forces the fuel.5 MPa (3.. the se- combustion chamber at high pressure. the bustion chambers. Together Exhaust treatment with the drawn-in air. functional requirements such as the regener- ation of the accumulator-type catalytic con- Generation of high-pressure verter. These are then reduced operation or stratified-charge operation). This measure reduces the now at high pressure. Simi. mainder of the cylinder is filled with either freshly drawn-in air. or a strati. the fuel In order to operate with maximum effi- is injected in such a manner that an A/F ciency.0. The electric fuel pump delivers fuel to the high-pressure pump (Fig. The overall A/F mixture then has ltotal λtotal > 1. The excess air permits “unthrottled” high-pressure pump then generates the sys. and on the other it depends upon A/F-mixture formation).. into the rail (4) where pumping (exhaust and refill) work. inject the fuel directly into the com. rail”) and. operation.. the torque. The injected fuel is finely atomized due to the very high injection pressure.. Robert Bosch GmbH Gasoline direct injection: Operating concept 55 Operating concept The various methods of running the engine Gasoline direct-injection systems are charac.. In homogeneous operation at λ ≤ 1. the 3-way catalytic converter needs a mixture with λ ≤ 1 is evenly distributed stoichiometric A/F mixture. is a function of engine speed and desired tion takes place inside the cylinder (internal torque. the re. gasoline direct-injection engine for the most part behaves the same as a manifold-injec- A/F-mixture formation tion engine. sumption. upon the engine’s operating mode. therefore also serves to lower the fuel con- The fuel pressure is measured by the high. Torque mary pressure of 0. when triggered by the engine ECU. to nitrogen. lection of the operating mode to be applied lar to the diesel engine. also at part load. Due to excess throughout the complete combustion cham. Pos. λ > 1 and homogeneous A/F-mixture distri- bution. On the one hand. A/F-mixture forma.3. air.12 MPa by the pressure-control In homogeneous and lean-burn operation at valve (8). or with a very lean A/F mixture. running the engine briefly with excess air. lean-burn operation results in increased ber (homogeneous operation). During stratified-charge operation. with inert gas returned to the cylinder by EGR. and it is stored until required for injection. the in- Depending on the engine operating point jected fuel mass is decisive for the generated (required torque and engine speed). pressure sensor (6) and adjusted to values between 5.. .0. injectors). nor at its In order to prevent the fuel mixing with an interfaces.. high-pressure pump Rail High-pressure pumps The rail stores the fuel delivered by the high. Assignment pressure pump and distributes it to the It is the job of the high-pressure pump high-pressure fuel injectors. weight etc. pressure-control flow pulsation means so that there is very valve. Design and con.) are specific to the engine and the system. (HDP) to compress the fuel delivered by the ume is sufficient to compensate for pressure electric fuel pump at a primary pressure of pulsations in the fuel circuit. The minimal level of pumping- (high-pressure pump. 1 Three-cylinder high-pressure pump HDP1 (axial section) 4 5 3 6 2 7 1 Figure 1 1 Eccenter cam 8 2 Sliding block 9 3 Pumping element with pump piston (hollow piston.3. The high The rail is provided with connections for a pressure is built up when the engine runs up number of the injection-system components to speed. The rail’s vol. high-pressure injection. oil lubricant. dimensions. the fuel is injected at the primary pressure.12 MPa) needed for the An aluminum rail is used. It must provide enough fuel at the pressure (5. 0.. high-pressure sensor. struction (volume. when starting the engine. Initially. Robert Bosch GmbH 56 Gasoline direct injection: Rail.5 MPa. the high-pressure pump is cooled and lubricated by fuel. fuel inlet) 13 4 Sealing ball 10 5 Outlet valve 6 Inlet valve 7 High-pressure con nection to the rail 8 Fuel inlet (low presure) 12 9 Eccenter ring 11 æ UMK1785Y 10 Axial face seal 11 Static seal 12 Driveshaft . high-pressure little pulsation in the rail.. Construction guarantees that there are no leaks in the rail itself. 1) 1 Eccenter cam 2 Sliding block 3 Pumping element æ UMK1784Y with pump piston 5 Outlet valve 6 Inlet valve 9 Eccenter ring Three-cylinder high-pressure pump The use of three pump cylinders at an angle HDP1 of 120° to each other results in very low lev- There are many different types of high-pres. When the piston moves fuel is forced out to the high-pressure con.0. When the piston HDP2 moves upward this volume of fuel is com. When the piston moves upwards this volume . The de- sure pumps available. Fig. The pressure-control valve releases cylinders. through the inlet valve and into the pump cylinder.5 MPa from the fuel line through the hollow pump piston and the inlet valve (6) Single-cylinder high-pressure pump into the pump cylinder. and Fig. of 0.. at maximum delivery driveshaft (12) rotates with the eccenter cam the high-pressure pump delivers slightly (1) which is responsible for the up and more fuel than the maximum needed by the down motion of the pistons (3) in their engine. the pressure of the excess fuel and then di- ward. fuel flows at the primary pressure nection (7). When the piston moves down. fuel flows at the primary pressure of rects this into the return line.3. So that there is always enough the HDP1 three-cylinder radial-piston fuel available..5 MPa from the fuel line. The HDP2 single-cylinder pump is a cam- pressed and when the rail pressure is driven radial-piston pump with variable de- reached the outlet valve (5) opens and the livery quantity.3.. Driven by the engine camshaft. the warm-up in the rail. downward. and in order to limit the fuel pump. Robert Bosch GmbH Gasoline direct injection: High-pressure pump 57 2 Three-cylinder high-pressure pump HDP 1 (cross-section) 2 cm 6 7 3 4 2 10 1 Figure 2 (Position numbers identical to Fig. 2 a cross section through tional speed.0. 1 shows an axial livery quantity is proportional to the rota- section. 0. els of residual pulsation in the rail.. The excess fuel deliv- back into the fuel inlet. The pressure-control valve is located be- gerable delivery-quantity control valve. This is a safety measure The maximum delivery quantity (l/h) is a to ensure adequate rail pressure in case of function of the rotational speed. incorporated to prevent excessive rail pres- ments by triggering the control valve ac. Robert Bosch GmbH 58 Gasoline direct injection: High-pressure pump. as the pressure-control valve in the three- cylinder HDP1 pump. sure which could otherwise damage the cordingly. pressure-control valve of fuel is compressed and forced into the rail as soon as it exceeds the rail pressure. Pressure-control valve The pump chamber and the fuel inlet are Assignment connected with each other through a trig. 3). It adjusts end of the delivery stoke. 1 Section through the pressure-control valve 1 2 3 Figure 1 1 Electrical connec- tion 4 2 Spring 3 Solenoid coil 4 Solenoid armature 5 Seal rings (O-rings) 5 6 Outlet passage 6 7 æ SMK1812Y 7 Valve ball 5 8 Valve seat 8 9 Inlet with inlet 9 strainer . the pressure in the the required pressure in the rail by changing pump chamber collapses and the fuel flows the flow cross-section. circuit. A pressure-limiting function is tity can be adjusted to comply with require. Pos. and the cam lift. Once the required rail pres- sure is reached the valve opens and prevents With no current flowing. components. been completed. If tween the rail and the low-pressure side of this valve is triggered and opens before the the HDP1 high-pressure pump. This means that the ered by the HDP1 flows into the low-pres- delivery-control valve has the same function sure circuit. the number malfunction in the electrical-triggering of cams. The non-return valve between the pump chamber and the rail prevents the rail pres- sure dropping when the delivery-quantity control valve opens. The valve ball (7) lifts from quantity control valve remains closed from the valve seat (8) and in doing so changes pump-cam BDC until a given stroke has the valve’s flow cross-section as required. the (Fig. The delivery quan. Design and operating concept The solenoid is triggered by a pwm signal In order to adjust the delivery quantity. 1. the pressure-con- further pressure increase in the rail. trol valve is closed. and noise. V Design and operating concept A steel diaphragm is at the heart of the rail- pressure sensor. 12 MPa (50 .5 æ UMK0719-2E As soon as the pressure to be measured is applied to one side of the diaphragm via the 0 pmax pressure connection (4) the deformation. the measuring accuracy is below 2% 2 of the measuring range.. 120 bar). Pressure dependent resistors change their values due . dependent resistors p 4 Pressure connection
Gasoline direct injection MED-Motronic 5 Mounting thread The working pressure in such a gasoline direct injection system is a function of the 2 Rail-pressure sensor: Charcteristic curve (example) torque and engine speed. 20 µm at 1500 bar). 80 mV output voltage signal The rail-pressure sensors used in the Com. This is then passed on to fuel reservoir (fuel rail). together with a ing the stipulated fuel pressure in the rail is stored characteristic curve. the ECU which uses it. 3). Precisely maintain. toxic emissions. It is 5 . and thinner ones for lower pres- sures). 1 Electrical connec- jection system tion (plug) 5 2 Evaluation circuit The maximum working pressure pmax æ UMK1576-1Y 3 Steel diaphragm (rated pressure) is 160 MPa with deformation- (1600 bar). By means of collecting Assignment leads. evaluation circuit (2) in the sensor and am- sure the fuel pressure in the high-pressure plified to 0 . Fuel pressure is controlled in a special 1 Rail-pressure sensor (design) control loop. generated by the bridge is transferred to an mon Rail and MED-Motronic systems mea.... 2) engine’s power output. Robert Bosch GmbH Gasoline direct injection: Rail-pressure sensors 59 Rail-pressure sensors to the bending of the diaphragm (approx. 1 Very tight tolerances apply to the rail-pres- sure sensors. Pos.. The sensor’s measuring range is a function of the diaphragm thick- ness (thicker diaphragms are used for higher pressures. 1 4
Common Rail diesel accumulator-type in. to calculate the of extreme importance with respect to the pressure (Fig. 1. the 0 .. Deformation-dependent 4. deviations from desired value being compensated for by an open-loop or 2 cm closed-loop pressure-control valve.5 measuring resistors are vapor deposited on Output voltage the diaphragm in the form of a bridge cir- cuit (Fig.. and in the main operating range. 0.. 5 V. 3 Rail-pressure sensors are used with the fol- lowing engine systems: Fig. the spring forces the needle back down against its seat and injection stops. or noid coil is energized (current flows). De. 5 improved precision of spray alignment. Excellent fuel atomisation is achieved thanks to the special nozzle geome- 2 try at the injector tip. 5 Injector housing 6 Nozzle needle with æ UMK1782Y solenoid armature 7 7 Valve seat 8 8 Injector outlet passage . gasoline direct injection can boast faster injection. the injected fuel quantity is therefore dependent upon the rail pressure. against the force of the spring and opens the injector outlet passage (8).
Nozzle needle with solenoid armature (6). and better formation of the fuel spray.
Solenoid (4). means of the fuel’s atomisation achieve con. Robert Bosch GmbH 60 Gasoline direct injection: High-pressure injector High-pressure injector Design and operating concept The high-pressure injector (Fig. 3 4 Compared to manifold injection. trolled mixing of the fuel and air in a spe. 1) com- Assignment prises the following components: The high-pressure injector represents the in- terface between the rail and the combustion
Injector housing (5). and the length of time the injector remains open. The injector opens very quickly. Taking a given opened cross-sec- tion. and by
Valve seat (7). and closes against the rail 1 pressure. the fuel is either concentrated in the vicinity A magnetic field is generated when the sole- of the spark plug (stratified charge). lifts the valve needle from the valve seat tion chamber (homogeneous distribution). and cific area of the combustion chamber. chamber. pending upon the required operating mode.
Spring (3). guaran- 1 High-pressure injector (HDEV): Design tees a constant opened cross-section during the time it is open. When the energising current is switched off. Figure 1 Technical requirements 1 Fuel inlet with fine Compared with manifold injection. the counter-pressure in the combustion cham- ber. Its job is to meter the fuel. gasoline strainer 2 Electrical direct injection differs mainly in its higher 6 connections fuel pressure and the far shorter time which 3 Spring is available for directly injecting the fuel into 4 Solenoid the combustion chamber. Fuel is then in- jected into the combustion chamber due to the difference between rail pressure and combustion-chamber pressure. This evenly distributed throughout the combus. The injector must be triggered with a highly 2 Comparison between gasoline direct injection and 3 Signal characteristic for triggering the HDEV manifold injection high-pressure injector Manifold injection Gasoline direct 1 a injection 0 Imax b Premagnetization Ivm. A special trigger- ing module uses this signal to generate the In the case of gasoline direct injection actual triggering signal (b) with which the though. only half a crankshaft rotation 50.000 min–1. With manifold injec. simply a digital signal (a). the in- (factor 1:12).5 5 20 c Needle lift Duration of injection in ms d Injected fuel quantity . this needle can lift off of the valve seat very corresponds to an injection duration of only quickly (c). With the is far lower than with manifold injection needle’s opened position constant. tion. HDEV driver stage triggers the injector.90 V trigger voltage which is high is available for the injection process. 0. considerably less time must suffice. Robert Bosch GmbH Gasoline direct injection High-pressure injector 61 Fig. enough to provide a high current at the start Referred to the same engine speed as with of the switch-on process so that the valve manifold injection (6. only a very low trig- For gasoline direct injection..4 ms. (Fig. jection duration (d). The initial triggering signal from fold. At idle. tvm Current Ivm Ih Injected fuel quantity WOT tvm c Needle lift Figure 2 Injected fuel quantity as a function of the duration 0 ton toff of injection d Injected quantity Figure 3 a Triggering signal fuel æ UMK1777E æ SMK1772E Idle b Injector current 0 Duration of injection characteristic 0.000 min–1).. the fuel gering current suffices to maintain the nee- requirement at idle referred to that at WOT dle at a constant opened position. 2 underlines the technical demands complex current characteristic in order to made on the injector. 3). At an engine speed of 6. The calculations for the duration of injec- Triggering the HDEV high-pressure tion take into account the premagnetisation injector time before the valve needle actually lifts. this the microcontroller in the engine ECU is corresponds to 20 ms. (maximum needle lift). During homogeneous operation. the fuel must be injected in the induction stroke. comply with the requirements for defined. jected fuel quantity is proportional to the in- tion duration of approx. Once the valve needle has lifted 5 ms. In A booster capacitor is used to generate the other words.4 3. two revolutions of the crankshaft are reproducible fuel-injection processes available for injecting the fuel into the mani. this results in an injec. In order to obtain the the spray direction is precisely aligned. Two basically different combustion Wall-guided combustion process processes are possible: In the case of the wall-guided process. Tumble air flow This process produces a cylindrical air flow. In order to be able to ignite the A/F tion chamber. flows of air are generated in the and injector are exactly positioned. Swirl air flow The air drawn by the piston through the open intake valve and into the cylinder gen- erates a turbulent flow (rotational air move- ment) along the cylinder wall (Fig. it is imperative that spark plug concerned. and that combustion chamber. the injector in. required charge stratification. This process is also designated “swirl combustion b process”. 1a). Robert Bosch GmbH 62 Gasoline direct injection Combustion process Combustion process Spray-guided combustion process The spray-guided process is characterised by The combustion process is defined as the the fuel being injected in the spark plug’s way in which A/F-mixture formation and immediate vicinity where it also evaporates energy conversion take place in the combus. (Fig. one differentiates between two possible flows of 1 Air-flow conditions for the various combustion air which are the result of specific intake- processes port and piston design. that it arrives there at the moment of ignition. c Figure 1 a Spray-guided b Wall-guided swirl air æ UMK1778Y flow c Wall-guided tumble air flow . The injector injects a into this air flow which transports the resulting A/F mixture to the spark plug in the form of a closed A/F-mixture cloud. the spark plug is sub- jects the fuel into the air flow in such a man. 1c). 1b). With this process. The since under certain circumstances the hot air flow then transports the A/F-mixture spark plug can be directly impacted by the cloud in the direction of the spark plug so relatively cold jet of injected fuel. or tumbling air flow. which in its movement from top to bottom is deflected by a pro- nounced piston recess so that it then moves upwards in the direction of the spark plug (Fig. mixture at the correct moment in time (ig- Depending upon the combustion process nition point). jected to considerable thermal stressing ner that it evaporates in a defined area. The ignition point is a combustion chamber. . function of injection pressure and combus- All fuel must have evaporated before a gas tion-chamber pressure. then vaporize quicker. Taking a constant ence this process: combustion-chamber pressure. an A/F wall. function of the engine speed and the charge operation on the other hand. Since gasoline cannot evaporate point. and the injector to the combustion-chamber combustion-chamber geometry. sive for the stratified-charge mode. mixture is only homogeneous within a re- stricted area. this means all. The penetra-
Fuel-droplet size. the so-called penetration depth increases along with
Combustion-chamber temperature. or it is incomplete. this A/F mixture is distributed the combustion chamber. A number of factors influ. This is why the fuel is injected during the compres- Technical requirements sion stroke so that a cloud of A/F mixture is In the “homogeneous” mode of operation generated which can be transported to the (homogeneous λ ≤ 1 and homogeneous vicinity of the spark plug by the air flows in lean-burn). The intake air can then assist in achieving rapid evaporation of the fuel and efficient ho- mogenisation of the A/F mixture. and tion depth is defined as the distance trav-
The time which is available for fuel evapo.. while the remaining areas of Penetration depth the combustion chamber are filled with in. During stratified. vaporizes completely. Robert Bosch GmbH Gasoline direct injection A/F-mixture formation 63 A/F-mixture formation A/F-mixture formation in the stratified- charge mode Assignment The configuration of the combustible A/F- It is the job of the A/F-mixture formation to mixture cloud which is in the vicinity of the provide a combustible A/F mixture which is spark plug at the instant of ignition is deci- to be as homogeneous as possible. that under these conditions more fuel must be injected in order to obtain a combustible A/F mixture. pressure. The cylinder wall or the piston will be Influencing factors wetted with fuel if the distance needed for Temperature influence full vaporization exceeds the distance from Depending upon temperature.. increasing injection pressure. The fuel-droplet size in the injected fuel is a ert gas or fresh air. the A/F required torque.6.1. either no combustion takes place at completely at low temperatures. If the fuel on the cylinder wall and pis- mixture (air/gasoline) is combustible at ton has not vaporized before the ignition λ = 0. This is why the fuel is injected in the induction stroke during homogeneous operation. and by the piston homogeneously throughout the whole of the as it moves upwards. Higher injection mixture or gas-vapor mixture can be termed pressures result in smaller droplets which homogeneous.6. A/F-mixture formation in the homogeneous operation mode The fuel is injected as soon as possible so that the maximum length of time is avail- able for formation of the A/F mixture. elled by the individual fuel droplet before it ration. engine is operated in the homogeneous operating ranges tor injects the fuel during the compression mode λ = 1 (in exceptional cases with λ < 1) B Lean-burn or homo. During actual driving. the recirculated exhaust gas reduces the sible adaptation for each and every engine combustion temperature and. tween operating modes since these take place without torque surge. so that λ = 1 with EGR. and when accelerating gently charge stratification and efficient transport (slight changes in torque with increasing en. the lowers the temperature-dependent NOx driver does not notice the change-overs be. stratified-charge mode. level is high.
Homogeneous mode. emissions. In this operating mode. in exceptional cases. In the case of excessive when accelerating strongly (pronounced torque. Due to the late injection point. operating state. Operating modes A with dual injection: Since the whole of the combustion cham- ce ber is utilised. this operating mode there is sufficient time for the A/F mixture is possible in area C 1 Operating-mode characteristic curves for gasoline to be distributed throughout the whole of direct injection and area D the combustion chamber. Here. engine speed). instead of in the stratified-charge mode. the homogeneous mode is re- Acceleration C Stratified-charge/ D B istan ves res r quired when high levels of torque are de- Torque M cat-heating mode. If engine speed is too high. 3000 min–1. In this operating mode. the injec. has E slightly excessive fuel (λ ≤ 1). The untreated NOx
Homogeneous/anti-knock. chamber. Referred to the combustion chamber as a
Homogeneous and lean-burn. 1) show “Torque” define the limits for stratified- which operating modes are passed through charge operation. whole. During the brief period before the ignition jection starts in the induction stroke. . . cu C ad same area as Ro manded. soot is generated due to zones of lo- changes in torque with at first unchanged cal rich-mixture. emissions stratified-charge of untreated exhaust gas are also low due to operation with EGR the stoichiometric A/F mixture. there is gasoline direct injection (Fig. D Homogeneous and æ SMK1773E In homogeneous operation. as a result. the A/F mixture is very lean in the
Homogeneous and stratified-charge. Homogeneous mode this operating mode prox. The parameters “Engine speed” and The lines in the diagram (Fig. In the lower torque range at speeds up to ap. longer be maintained due to excessive tur- bulence. of the A/F mixture to the spark plug can no gine speed). The injected fuel C Stratified-charge mass is such that the A/F mixture ratio is operation with EGR stoichiometric or. Figure 1 Stratified-charge mode A Homogeneous operation with λ = 1. combustion stratified-charge E Homogeneous/anti- to a great extent corresponds to the combus- Engine speed n knock tion for manifold injection. 1): not sufficient time to distribute the A/F mix- ture throughout the complete combustion
Stratified-charge mode. whereby These operating modes permit the best-pos. the engine is operated in For high torques and high engine speeds the is possible in all the stratified-charge mode. In- geneous operation. the best remedy is to use a high EGR rate. emissions are very high when the excess-air
Stratified-charge/cat-heating. Robert Bosch GmbH 64 Gasoline direct injection Operating modes Operating modes point the air flow in the combustion cham- ber transports the A/F mixture to the spark There are six operating modes in use with plug. stroke shortly before the ignition point. and then leads to a richer zone forming in the area of again in the combustion (power) cycle the spark plug. Here. avoid “knock”. mixture is generated by injecting a small therefore. in stratified-charge operation with quantity of fuel during the induction stroke. converter. once in the compression stroke (similar to tion) during the compression stroke. mode with λ ≤ 1. jection is approx. ing up of the NOx catalytic converter to tem- charge and homogeneous mode. This stratified charge is easily whereby the fuel injected here combusts ignitable and then ignites the rest of the ho. temperature. the NOx emissions heating methods the high temperature are also reduced. although this must be optimized with a homogeneous lean A/F mixture. In this operating mode. The homogeneous and stratified-charge mode is activated for a number of cycles A further important application is for heat- during the transition between stratified. Stratified-charge/cat-heating Homogeneous and stratified-charge Another form of dual injection makes it mode possible to quickly heat up the exhaust-gas The complete combustion chamber is filled system. At the geneous and lean-burn mode. Here. peratures in excess of 650 °C as needed to ables the engine management system to bet. in the homo. can be dispensed with. Since the pumping losses are gle shift in the retard direction as needed to lower due to “non-throttling”. . high levels of excess air. That is. as well as lowering fuel consumption com- pared to homogeneous operation. same time. the use of dual can be run with a homogeneous lean A/F injection at WOT. Robert Bosch GmbH Gasoline direct injection Operating modes 65 Homogeneous and lean-burn mode Homogeneous/anti-knock mode In the transitional range between stratified. it is imperative that dual Due to the conversion to energy of the very injection is used since with conventional lean A/F mixture λ > 2. injection takes place Fuel is injected a second time (dual injec. fuel con. which is required here cannot always be The distribution factor between each in. reached in all operating modes. This before this solution can be applied. initiate the desulphurization of the catalytic ter adjust the torque during the transition. Steady-state operation using dual injec- tion at low engine speeds in the transitional range between stratified-charge and homo- geneous mode reduces the soot emissions compared to stratified-charge operation. the engine stratification hinders knock. together with ignition-an- mixture (λ>1). 75 % of the fuel is injected in the first injection which is responsible for the homogeneous basic A/F mixture. very late and thus heats up the exhaust side mogeneous mixture in the remainder of the and the exhaust system to a very high combustion chamber. since the charge charge and homogeneous mode. This en. the favorable ignition point also sumption is lower than in the homogeneous leads to higher torque. This the “stratified-charge mode”). 75 %. Inductive ignition systems Conventional coil ignition (CI) Transistorized ignition (TI) Electronic ignition (EI) Distributorless æ UMZ0307E semiconductor ignition Mechanical Electronic . but also for triggering the ignition spark at exactly the right in. It defines the ignition point and there. the ignition energy is temporarily stored in the ignition Survey coil’s magnetic field and after having been transformed to a high enough voltage it is The most important characteristic values for transferred to the A/F mixture at the igni- the ignition of the A/F mixture are: tion point. energy storage are available for use with rac- ing and high-performance engines. A given voltage across the spark-plug elec- combustion engine with spark ignition (SI). Following the spark discharge. this spark discharge. must be ex- An ignition spark is used to ignite the com. Here. ing on the engine’s operating point and the The ignition spark is in the form of a spark condition of the spark plug. This was. fore the inflammation or burning of the A/F mixture. ceeded in order to generate the ignition pressed A/F mixture in the combustion spark in the combustion chamber. In this form of ignition. there has been no letup in ignition-system devel- opment. and Ignition systems with capacitive high-power
Ignition energy. voltages as high discharge between the spark-plug electrodes as 30. Depend- chamber and thus initiate its combustion. needed. 1). to the forefront in passenger-car applica- tions. the The ignition system is not only responsible spark energy is transferred to the A/F mix- for generating the high voltage needed for ture and initiates the combustion process. and is. electronics is continuing to (timing) play a more and more important role αz (Fig. the ignition voltage. Inductive (coil) ignition systems have come stant in time. field of a capacitor. It also has considerable influence Ignition systems: on the gasoline engine’s output power and Development its exhaust-gas emissions. Robert Bosch GmbH 66 Ignition: An overview Survey.000 V (turbocharged engine) are which extend into the combustion chamber. These The ignition angle is referred to crankshaft store the ignition energy in the magnetic TDC.
Ignition angle. the result of the 1 The development of the ignition system ever-increasing demands made for higher engine outputs and improved exhaust-gas Switch ignition. Since they first came onto the market.Ignition-angle High-voltage coil current adjustment distribution emissions. trodes. ignition-systems development Ignition: An overview The Otto-cycle engine is a gasoline internal. Robert Bosch GmbH Ignition: An overview Ignition-systems development 67 Conventional coil ignition (CI) Electronic ignition (EI) (1934 . the ignition system no longer contains any tor mounted in a transistorized trigger box. Fig. 2 Section through a 4-cylinder engine with gasoline direct injection and distributorless semiconductor ignition 1 2 æ UMM0561Y Figure 2 1 Spark-plug ignition coil 2 Spark plug . the mechanical ignition timing through the ignition coil (charge coil and ig. voltage distribu- Transistorized ignition (TI) tion is no longer mechanical. with microcontroller is needed for triggering A mechanical rotor which rotates inside and control. components which are subject to wear. 1998) With this ignition system. is dispensed with. 2). The transistor is triggered by an inductive or As from 1998. 1998) Mechanical breaker points in the ignition Although high-voltage distribution is still distributor control the flow of current mechanical. Engine speed and load are nition).. put variables for an ignition map stored in a nition angle as a function of engine speed semiconductor memory.. The use of a transistor for have been equipped with an engine ECU switching means that the disadvantages due which combines distributorless semiconduc- to wear at the mechanical breaker points are tor ignition and gasoline injection avoided.. This means that placed here by a non-wearing power transis. 1986) (1983 . (static voltage distribution). 1993) formed electronically by the ignition ECU The mechanical breaker points were re. (1983 ... the ignition distributor is responsible for distributing the high voltage to the spark Distributorless semiconductor ignition plugs (rotating high-voltage distribution). (Motronic... but is per- (1965 . all newly designed engines Hall sensor.. A mechanical (flyweight) advance measured electronically and used as the in- mechanism and a vacuum unit define the ig. An ignition ECU and load (mechanical ignition timing). 1. Fig. Robert Bosch GmbH 68 Coil ignition Survey. of current in case of fault (e. Ignition driver stage tion system is responsible for the spark dis- charge at the spark-plug electrodes. Pos. Due to the costs in- volved. age distribution and double-ended ignition coil as an example. lithically in the driver stage and serve to pro-
Ignition coil (2).
Spark plug (4). 1 shows the basic design of the common for the driver stages to be incorpo- ignition circuit rated in the ignition coil. tect the ignition components against over-
High-voltage distributor. Fig. 1 Using a coil ignition system with static voltage In addition. and for Assignment the provision of enough energy for a power. short circuit). outside temperatures are high. It is the job of the ignition driver stage to ful spark. and the latter are located in their own housing outside the engine ECU.4a terminal æ UMZ0308Y designations Triggering for the ignition driver stage .g. it is becoming increasingly distribution and double-ended ignition coils as an example. Survey Design and operating concept These driver stages are mostly in the form of The ignition circuit of the coil ignition com.4. are available. ignition driver stage Coil ignition The gasoline engine’s (inductive) coil igni. external driver stages are no longer used on new developments. Primary-cur- rent limitation is only needed for limitation Using a coil ignition system with static volt. 1). it is necessary that appropriate measures are Modern ignition systems with static voltage taken to ensure that the power loss is reliably distribution are no longer equipped with dissipated to the surroundings even when high-voltage distributors. the permissible operating temperatures. The former are integrated on the engine ECU printed-circuit board. and During operation. 12V 15 3 4 2 Figure 1 1 Ignition driver stage 2 Ignition coil 3 EFU diode (EFU = Switch-on spark 1 4a 4 suppression) 1 4 Spark plug 15. The “primary- prises the following components: current limitation” and “primary-voltage limitation” functions are integrated mono-
Ignition driver stage (Fig. switch the ignition-coil current. load. In order not to exceed suppressors.1. 1 shows the principle Internal and external ignition-driver stages design of the ignition circuit. a 3-stage power transistor. driver stage and igni-
Connecting devices and interference tion coil both heat up. ment and location of the primary and sec. The design and construction of the ignition coil are adapted to the application in question. Today’s state-of-the-art ignition coils are comprised of two magnetically-coupled High-voltage generation copper windings (primary and secondary On modern ignition systems. while the other end is directly spark flashover at the ignition point. Depending upon design. 4a) is connected energy and generates the high voltage for the to ground. driver stage for the calculated dwell period. 15 15 4a 15 4a Figure 2 For rotating high-voltage On the single-ended ignition coils for sys- distribution: tems with rotating high-voltage distribution. So as to ensure efficient insulation be- tween primary and secondary winding. primary and sec- ondary windings are not connected. signed as a disc or chamber winding. The energy stored in the pri- mary winding’s magnetic field is transferred 2 Ignition coils: Schematic representations to the secondary winding by magnetic in- duction. Depending upon the turns ratio. The secondary winding’s other connec. The arrange. the core can be of during which the coil’s primary current in- either the closed type (compact coil). The distribution other end of the secondary winding is con. connected to the spark plug. an iron core assembled from management ECU switches on the ignition sheet-metal laminations. a Single-ended one of the primary-winding terminals is ignition coil connected to one of the secondary-winding A B terminals and then to Terminal 15 of the For static high-voltage driving switch (economy connection). On the Assignment double-ended ignition coil. In order to increase the insulation re. are decisive for the energy sistance. each secondary-winding Design terminal is connected to a spark plug. the engine- windings). or of creases to its desired value and in the process the rod type (rod-type coil). On the double-ended and dual-spark A Primary winding ignition coils used on ignition systems with B Secondary winding . one end of the The ignition coil stores the required ignition secondary winding (Term. b Double-ended 1 4 1 4 1 4b ignition coil nected to the ignition driver stage (Terminal æ UMZ0257-2Y c Dual-spark ignition 1). The magnitude of the primary current. Operating concept The ignition coil functions according to Faraday’s Law. coil tion goes to the ignition distributor (Termi- nal 4). and a plastic case. generates a magnetic field. a b c voltage and current are transferred from the primary to the secondary winding (Fig. Robert Bosch GmbH Coil ignition Ignition coil 69 Ignition coil static voltage distribution. the secondary winding can be de. On the dual- spark ignition coil. the case is filled with epoxy resin. 2). ondary windings depends upon the coil’s together with the ignition coil’s primary shape. inductance. stored in this magnetic field. and between the windings and the case. Pos. This is of opposite polarity to the high voltage. Fig. 3a. the coil’s turns ratio. the switch-on spark is effec- tively suppressed by the upstream distribu- 1 2 tor-rotor spark gap. the high voltage in- coil’s secondary winding. On systems with rotating high-voltage distribution. In the case of static volt- age distribution with double-ended ignition 3 4 coils.. the voltage generated by a single ignition coil The secondary voltage must in any case ex. There must be adequate spark energy available to ignite the This form of distribution no longer has any A/F mixture even when follow-up sparks are significance for modern engine-manage- generated. a diode (EFU diode. Rotating high-voltage distribution ver stage. voltage distribution.400 V self-induced voltage is generated 2 Ignition coiI 2 in the secondary winding. (required ignition voltage). 1. 2b) in the high-voltage circuit stops the switch-on spark. (Fig. the Figure 3 switch-on spark is effectively suppressd by a Rotating high-volt- the high flashover voltage required for the age distribution b Static high-voltage series connection of two spark plugs. Spark discharge at the spark plug (switch-on spark) must be 3 Principle of high-voltage distribution avoided at all costs at this point. the plug.. The resulting change in magnetic Assignment field induces the secondary voltage in the At the ignition point. when 7 6 5 dual-spark ignition coils are used. Addi- distribution with tional measures need not be taken. This is the responsibility of the high- winding capacitance. When the primary current is switched on. 2) is mechanically distributed ceed the voltage level required for the to the individual spark plugs (5) by an igni- flashover between the spark-plug electrodes tion distributor (3).2 kV is induced in the secondary winding (switch- on voltage). an undesirable voltage of approx. The maximum duced in the ignition coil must be available possible secondary voltage is a function of across the electrodes of the correct spark the energy stored in the ignition coil. In this form of high-voltage distribution. high-voltage distribution At the moment of ignition (ignition point) High-voltage distribution the ignition driver stage interrupts the cur- rent flow. double-ended 1 ignition coils When the primary current is switched off.. spark is diverted by mixture turbulence and “breaks off ” as a result. With static voltage distribution.. and the pri- mary-voltage limitation of the ignition dri. 3 Ignition distributor æ UMZ0309Y 4 Ignition cable 7 6 5 5 Spark plug 6 ECU 7 Battery . Robert Bosch GmbH 70 Coil ignition Ignition coil. These occur when the ignition ment systems. a 1 Ignition lock 200. the secondary load (spark plug). a Installations with dual-spark ignition coils One ignition driver stage and one coil are allocated to two cylinders. It is provided Installations with double-ended ignition with a ground electrode (2) and a center coils electrode (1). Each cylinder is allocated its own spark-plug ignition coil and ignition driver stage. When the ignition coils can be designed to be very ground electrode(s) is/are located to the side small. The cylin. surface-gap spark plug (d). Spark discharge takes place at each 1 Center electrode spark plug at the moment of ignition (igni. If this is accordance with the firing sequence. gastight high-voltage lead-through into the combustion chamber. these of an air-gap spark plug (a). EA Spark gap . 2 Ground electrode tion point). Robert Bosch GmbH Coil ignition Voltage distribution. Design and operating concept There are two versions of this form of volt. although 4 Spark plug (partial section) and spark gap this system must also be synchronized to the camshaft by means of a camshaft sensor. There are no limitations on the ignition-timing adjustment range. Although d side electrode 1 c Surface air-gap this precautionary measure leads to a limita- æ UMZ0129-1Y (air spark or surface tion in the the ignition-timing adjustment spark possible) range. they are mounted directly of the center electrode. lated. opposite to the center electrode one speaks Since there are no distributor losses. spark plugs 71 Static voltage distribution Spark plugs Mechanical components are dispensed with on distributorless (electronic or static) high. versally irrespective of the number of engine cylinders. 4) is a ceramic-insu- age distribution. The ends of the secondary winding are each connected to a spark plug in different cylinders. Preferably. the ignition-coil primary side. Assignment voltage distribution (Fig. Care must be taken that the a Air spark gap with spark which takes place during the exhaust front electrode stroke does not ignite residual gas or fresh b Air spark gap with gas which has just been drawn in. electrode air-gap spark plug (b) or in the The static voltage distribution with dou. The ignition The spark plug generates a spark which coils are connected directly to the spark ignites the A/F mixture in the combustion plugs and voltage distribution takes place at chamber. it is not necessary to synchronize the EA d Surface spark gap 2 system to the camshaft. This permits wear-free and loss-free voltage distribution. this results in a side- above the spark plug. b ders have been chosen so that when one cylinder is in the compression stroke the other is in the exhaust stroke (applies only for engines with an even number of cylin- c Figure 4 ders). The spark plug (Fig. The The type of spark is determined by the posi- engine ECU triggers the driver stage in tion of the ground electrode(s). surface air-gap spark plug (c) or the purely ble-ended ignition coils can be applied uni. 3b). Increasing the secondary-cir- S cuit resistance. Electrical connection and the spark gap between center and ground interference-suppressor electrode becomes conductive. the interference resistors are in- tegrated in the spark-plug connectors. every spark flashover at spark plug or igni- age increases as a result. electrodes. the spark. As soon as the required ignition voltage is exceeded. voltage distribution) is a source of interfer- ence. shielding the combustion chamber. age. though. The capaci- tances in the secondary circuit which have devices charged up to ignition voltage (spark plug. . 5) to the ignition voltage. In order to minimise the inter- ference radiation from the high-voltage cir- cuit.. the ignition cables must be kept as short plug electrodes are subject to wear as a result as possible. up until the end of the pre. The residual energy in the ignition coil nition coils which are not mounted directly then decays completely in a post-oscillation on the spark plug. high-voltage-proof of 1.0 3. Since. of the erosion stemming from the spark cur- rent and corrosion due to the hot gases in Interference suppressors. when high-voltage distribution is used.0 ms K Spark head Time Interference radiation can be even further S Spark tail reduced by partially or completely screening tF Spark duration the ignition system. for the ignition system. plastic-insulated. Figure 5 0 1. Fig. Ignition cable ignition cable.0 2. Within a typical spark duration Special. Independent of the tion distributor (in the case of rotating high- operating mode. leads to increased 0 energy losses in the ignition circuit and Approx 30 s therefore to lower levels of spark energy at æ UMZ0044E the spark plug. each high- voltage line represents a capacitive load Spark-plug wear which reduces the available secondary volt- During normal engine operation.2 ms. Robert Bosch GmbH 72 Coil ignition Spark plug. 30 µs. and ignition coil) discharge The high voltage generated in the ignition abruptly in the form of a spark across the coil must be delivered to the spark plug. the there must always be adequate secondary voltage in the ignition coil’s secondary voltage available from the ignition system to winding increases very rapidly (approx. the suppression resistors should be in- kV stalled as close as possible to the interference source. 15 Normally. in the distributor rotor. moment of ignition (ignition point). in the K plugs at the other end of the ignition cable 10 tF and. This wear enlarges The pulse-shaped discharge which occurs at the spark gap and the required ignition volt. are used with ig- tail). Interference suppression resistors in the high-voltage circuit limit the discharge 5 Voltage curve at the spark-plug electrodes peak current. reliably provide for this ignition voltage. the energy stored in the ignition cables with special plugs for contacting the coil is converted in a glow discharge (spark high-voltage components. Spark plugs are also Voltage 5 available which feature an integral suppres- sion resistor. electrical connection and interference-suppressor devices After interrupting the primary current at the scribed spark-plug replacement interval.. phase. capacitive discharge Energy E 30 20 Spark tail. It depends upon a place high demands on the ignition system. Ignition voltage U and a secondary induc- tance of 15 H. process bustion chamber. and in- provides the required ignition voltage irre. levels of toxic emissions. and therefore also the ignition point. Robert Bosch GmbH Coil ignition Ignition voltage. These requirements charge between them. ignition energy 73 Ignition voltage ignition of the mixture. mance engine operation coupled with low plug electrodes required to cause spark dis. Good A/F-mixture ignition is the prerequisite for high-perfor- This is the level of voltage across the spark. The energy stored in the ignition coil is re-
Composition of the A/F mixture (excess. number of factors: Energy balance of a single ignition
Density of the A/F mixture in the com. . inductive discharge Figure 6 10 The energy values apply for an imaginary ignition system with an ignition- æ SMZ0310E coil capacity of 35 pF. The energy E which is stored in the ignition circuit’s secondary-side capacity C. Fig. This energy is divided into two differ-
Flow velocity and turbulence. 6 therefore shows a square-law curve. ent sections.
Electrode material. leased as soon as the ignition spark is initi- air factor. creases as the square of the applied voltage U spective of operating conditions. ated. The igni- tion energy has a decisive influence upon the 6 Energy balance of an ignition process without shunt. Spark head
Electrode gap.
Electrode geometry. an 0 5 10 15 20 25 30 35 40 kV external load of 25 pF. resistance and Zener losses mJ Available energy 40 Spark head. (E = 1/2 CU2). Lambda value). Ignition energy The breaking current and the ignition-coil parameters define the energy stored by the ignition coil and then made available as ig- nition energy in the ignition spark. is re- Care must be taken that the ignition system leased abruptly at the ignition point. for each individual ignition energy stored in the ignition coil. Fig. tances which can be caused by contamina- tion at the high-voltage connections. Further en- Further increases in the required voltage ergy is required to compensate for losses. provided that the coil (inductive share) is then released. 0. Under such conditions. A and ignition lines. re-ignite a needed to generate the high-voltage spark flame that has been extinguished. 6 on the previous page shows a simpli. and in order to maintain the suffices to generate a spark discharge and spark for a given period of time. the stratified-charge mode with gasoline di- tions. . lead to the misfire limit being reached. the energy stored in spark. as well The more air there is in a lean A/F mixture. or lean mixtures need more than 3 mJ.. discharge at the ignition point. must also be provided by the ignition coil. This fact spark plug projecting into the combustion leads to a particularly high level of energy chamber. On conventional ignition systems. as by deposits and soot on the parts of the the more difficult it is to ignite it. cause losses which are number of follow-up sparks are then needed then not available as ignition energy. as long as necessary. homogeneous and energy is the difference between the total stoichiometric. nition voltage. the larger is the proportion of total energy in the spark head. These re- decays away as a damped oscillation quirements amount to ignition energies of (ignition misfire). Robert Bosch GmbH 74 Coil ignition Ignition energy Spark tail Igniting the A/F mixture The rest of the energy stored in the ignition Under ideal conditions. and this energy Further losses result from shunt resis. rect injection.. when the required igni. when high break-down voltages are con- pletely burn an already ignited A/F mixture cerned. The energy that is actually required to ignite In certain cases. by means of follow-up sparks. quired to ignite the mixture by means of electric spark. the A/F mixture does not ignite and this leads to combustion misses. to ignite the A/F mixture. If insufficient energy is available. the higher are the currents which are lost through shunt resistances. The suppression resistors themselves. energies in excess of 15 mJ are or.2 mJ is re- energy released by capacitive discharge. rich This means that the higher the required ig. and the process an energy of approx. A/F-mixture turbulences such as occur in fied representation of the existing condi.. at least 30. can divert the ignition spark and the ohmic resistances in the ignition coil to such an extent that it extinguishes. The due for instance to contamination shunts at available energy in the spark head no longer the spark plugs. This A/F mixture is stationary. being needed on the one hand to cover the The severity of the shunt losses depends higher ignition-voltage requirements. the A/F mixture (the ignition energy) is only tion voltage is very high due for instance to a fraction of the total energy in the ignition badly worn spark plugs.120 mJ Shunt losses stored in the ignition coil. a figure which corre- sponds to an energy level of 60. The on the other to ensure that spark duration is higher the voltage applied to the spark plug. the spark tail no longer suffices to com. and upon the required ignition voltage.50 mJ.. creasing engine speed. 40 1 2 20 Za 3 Zc Figure 7 Zb 1 Ignition Za at the 0 right moment in time æ UMZ0001E 75° 50° 25° 0° -25° -50° -75° 2 Ignition Zb too early Ignition angle α Z (combustion knock) 3 Ignition Zc too late . and a wide electrode lag so that the ignition point has to be ad- gap. ignition point 75 These facts mean that enough ignition en. 60 BTDC ATDC Combustion-chamber pressure verter can also be damaged. of injection and the time needed for A/F- posits) during the time in which the high mixture formation during the compresion voltage is being built up. as do an extended spark accordingly. In such cases. and with it the rapid and complete taken that the engine does not knock combustion of all the A/F mixture. ignition must also take place at an earlier and earlier point re- Influences on the ignition characteristic ferred to the crankshaft angle. If the spark plugs are rect injection). These figures apply as the spark plug can suffice to initiate ignition long as the A/F mixture composition re- and combustion of the rest of the A/F mix. Therefore. This reduces the stroke. Turbulence supports rapid the peak pressure. high voltage. Mixture turbulence can also be an ad. igniting a moment the ignition spark is generated and small A/F-mixture cloud in the vicinity of complete combustion. Ignition point ergy must be made available so that the A/F mixture ignites reliably even under the most About two milliseconds elapse between the adverse conditions. The catalytic con. vanced even further. 7 Pressure curve in the combustion chamber for different ignition angles (ignition points) tion misfire if the spark plugs are badly con- taminated or wet. mixture’s ignition characteristic deteriorates tion characteristic. Ignition misfire leads to combustion miss bar which increases both fuel consumption and exhaust-gas emissions. 7). In extreme cases. shortens the spark duration. and with it be needed. Robert Bosch GmbH Coil ignition Ignition energy. the range for the variation of very dirty. In the stratified-charge mode (gasoline di- erable importance. and has a negative effect upon the exhaust gas. (Fig. along with in- ture in the cylinder. the ignition angle must be for follow-up ignition sparks should these chosen so that main combustion. mains unchanged. a long spark. this can lead to igni. takes place after Top Dead flame-front distribution in the combustion Center (TDC). Efficient mixture formation and ease of ac. Spark-plug contamination is also of consid. whereby care should be chamber. This leads to increased ignition duration. For the best-possible vantage provided enough energy is available torque output. energy flows from the ignition the ignition point is limited due to the end coil and through the spark-plug shunt (de. Poor cylinder charge means that the A/F cess to the ignition spark improve the igni. Lambda oxygen sensors (2. Inside the converter. work at maximum efficiency. Overview The oxygen needed for the burning process is already present in the case of a lean A/F Before leaving the exhaust pipe. These measured the USA at that time. 1. The oxidation converter cannot convert the Pos. the exhaust mixture (λ > 1) or by blowing air into the gas flows through the catalytic converter in. 3). A number of different catalytic-converter concepts were applied in the past years. special coatings oxides of nitrogen (NOx). Today. the hydro- haust gas is necessary in order to comply carbons and the carbon monoxide in the ex- with these limits. ensure that the toxic agents in the exhaust gas are chemically converted to harmless Oxidation-type catalytic converters were substances. catalytic con- values are then applied in adjusting the A/F verters which operate exclusively with oxida- mixture so that the catalytic converter can tion principles are used only very rarely. The three-way catalytic converter represents the state-of-the-art for engines with homoge- neous A/F mixture distribution and opera- tion at λ = 1. oxidation-type catalytic converter Catalytic emissions control Emission-control legislation defines the Oxidation-type catalytic limits for the toxic agents generated during the combustion process in the spark-igni- converter tion engine. Catalytic treatment of the ex. 1 Exhaust-gas tract with Lambda oxygen sensors and a three-way catalytic converter installed in the immediate vicinity of the engine Figure 1 1 Engine 2 Lambda oxygen sensor upstream of the catalytic con- verter (two-step sen- sor or broad-band 1 3 4 sensor depending upon system) 3 Three-way catalytic converter 4 Two-step lambda oxygen sensor downstreaam of the catalytic converter æ UMA0029Y 2 (only on systems with lambda two- sensor control) . stalled in the exhaust-gas tract (Fig. exhaust-gas tract upstream of the converter. 4) first introduced in 1975 in order to comply are used to measure the residual-oxygen with the exhaust-gas legislation in force in content in the exhaust gas. In this type of catalytic converter. Robert Bosch GmbH 76 Catalytic emissions control Overview. haust gas are converted by oxidation (burn- ing) into water vapor and carbon dioxide. Engines which run with a lean A/F mixture also require a NOx accumula- tor-type catalytic converter. G. CO creasing excess-air factor (Fig.025 1. for the A/F mixture ratio l is necessarily very ing the combustion of the A/F mixture: HC restricted.05 c Voltage characteris- nitrogen reduction and causes a sharp in. (2) 2 C2H6 + 7 O2 ➞ 4 CO2 + 6 H2O Operating concept (3) 2 NO + 2 CO ➞ N2 + 2 CO2 The toxic components are converted in two (4) 2 NO2 + 2 CO ➞ N2 + 2 CO2 + O2 phases: Firstly. Robert Bosch GmbH Catalytic emissions control Three-way catalytic converter 77 Three-way catalytic converter In order to maintain the three-way catalytic The three-way catalytic converter is installed converter’s conversion level for all three in the exhaust-emission control systems of toxic substances at as high a level as possible. or it is taken from the oxides of nitro- gen whereby these reduce as a result NOX (Fig. the concen- tration of these toxic components remains at c this low level. It is the job of circuit. Lambda control range Lambda-Regelbereich (catalytic-converter (Katalysatorfenster)window) tion. 2a). With high excess-air factors (λ > 1). Lambda sensor .0 1. The oxygen 2 Toxic components in the exhaust gas needed for the oxidation process is available in the exhaust gas in the form of the residual a oxygen resulting from incomplete combus. the con. Rich Excess-air factor λ Lean tic of the two-step crease in its concentration. This means that the A/F mixture composition must have a stoichio- Assignment metric ratio of λ = 1. Figure 2 Conversion of the oxides of nitrogen a Before catalytic (NOx) is good in the rich range (λ < 1) . A/F mixture formation must be (hydrocarbons). CO2 (carbon dioxide). G Reaction equations in the three-way catalytic ucts which result from this converion are converter H2O (water vapor). For carbon monoxide and hydrocarbons (HC). in the exhaust gas.975 1. The aftertreatment lowest levels of NOx are present during stoi. HC nents in the untreated exhaust gas. the carbon monoxide and the hydrocarbons are converted by oxidation (Fig. b version level increases steadily along with in. At λ = 1. CO (carbon monoxide). manifold-injection engines and gasoline these must be present in a chemical balance direct-injection engines. controlled by a Lambda closed-loop control and oxides of nitrogen (NOx). Equations 1 and 2). so that the “window” Three toxic components are generated dur. (1) 2 CO + O2 ➞ 2 CO2 and N2 (nitrogen). Equations 3 and 4). The concentration of the toxic substances in HC the untreated exhaust gas is a function of the CO excess-air factor λ (Fig. Even a small Uλ æ UMK0876-3E b After catalytic after- increase in the exhaust-gas oxygen content treatment as caused by operation at λ > 1 impedes the 0. the three-way catalytic converter to convert these into harmless components. (untreated exhaust gas) chiometric operation (λ = 1). The prod. 2b). NOX there is only a very low level of toxic compo. G. Rhodium accelerates the reduc- tion of the oxides of nitrogen (NOx). a catalytic converter contains about 1. and/or palladium. ing serves to increase the converter’s effec- ing by means of mineral swell matting (2) tive surface area by a factor of around 7000. verter) is an alternative to the ceramic tive catalytic noble-metal coating (4). the so-called “Washcoat” (4).3 g of noble metal. This coat- tension. and the ac. containing thousands of narrow passages through which the exhaust gas flows.. a substrate (5). 0.. Platinum most commonly used catalyst substrates. Depending upon the engine’s displace- ment. The Coating ceramic is a high-temperature-resistant The ceramic and metallic monoliths require magnesium-aluminum silicate. and palladium accelerate the oxidation of the hydrocarbons (HC) and of the carbon monoxide. At fective catalytic coating applied to the sub- the same time the matting also ensures a strate contains the noble metals platinum 100 % gas seal. which means less resistance to exhaust-gas flow. 3 Three-way catalytic converter with Lambda oxygen sensor 1 2 3 Figure 3 1 Lambda oxygen sensor 2 Swell matting 4 3 Thermally insulated double shell 5 O2 4 Washcoat (Al2O3 +N + CO substrate coating) HC æ UMA0027-1Y with noble-metal coating 6 5 Substrate (monolith) 6 Housing . a Ceramic monoliths fact which is important in the case of high- These ceramic monoliths are ceramic bodies performance engines. more passages can forefront be accomodated inside the same area. The mono. 3) comprises a The metallic monolith (metal catalytic con- steel casing (6). which expands the first time it is heated up On the oxidation catalytic converter. Two substrate systems have come to the Thanks to its thin walls. monolith. It is made of finely corrugated. is fastened inside a sheet-steel hous. an aluminum oxide (Al2O3) substrate coat- lith. Robert Bosch GmbH 78 Catalytic emissions control Three-way catalytic converter Design and construction Metallic monoliths The catalytic converter (Fig.05 mm thin metal foil which is wound and Substrates soldered in a high-temperature process. the ef- and firmly fixes the monolith in position. which is highly sensitive to mechanical ing. rhodium is also applied. On the three-way con- Ceramic monoliths are at present the verter. . Using Unleaded fuel the three-way catalytic converter. Residues from the engine oil can also distribution and at stoichiometric A/F ratio. one can still presume an aver- Installation point age pollutants reduction of more than 98 %. λ = 1. it is imperative that the Effectiveness ignition system is highly reliable and main. near the engine followed by a second (main) thermal aging is accelerated due to the sin. the pollu- Another prerequisite for long-term opera. Robert Bosch GmbH Catalytic emissions control Three-way catalytic converter 79 Operating conditions in the “retard” direction). needed for a high conversion level make it no worthwhile conversion of toxic sub.. shift of the timing . Lambda closed-loop control which monitors the composition of the A/F mixture. and this leads to a reduction engine demand that their coating techniques of the effective surface. Underfloor converters on the above 1000 °C thermal aging increases dras. installed close to the engine. The temperature conditions Considering a three-way catalytic converter. and oxides of nitrogen can be prac- lead compounds are deposited in the pores tically eliminated provided the engine oper- of the active surface and reduce their num. lation point. other hand.. Otherwise.. peratures melt the substrate and completely destroy the catalyst. verter. Since such tem. underfloor catalytic converter has come to tering of the noble metals and of the Al2O3 the forefront. tant emissions of carbon monoxide. Engine malfunction (ignition misfire) can An alternative is available with just one cause the temperature inside the catalytic “overall” catalytic converter which is then converter to exceed 1400 °C. The catalytic converter’s installation point is de- termined by such concepts (for instance. carbons. secondary-air injection. and in such cases interrupt the using a three-way catalytic converter is at fuel injection to the cylinder concerned so present the most effective emission-control that unburned A/F mixture cannot enter the method. For a spark-ignition engine with homoge- tenance-free. temperature) and good NOx conversion characteristics.1000 °C is of vital importance. The time spent at be optimized to provide for high-tempera- 800. and ture stability. 300 °C.800 °C is ideal with regard to In the case of the three-way catalytic con- high conversion levels and a long service life. Included in this system is the exhaust-gas tract. catalytic treatment of the exhaust gas bustion miss. Catalytic converters near the substrate layer. ates with homogeneous A/F-mixture ber. require optimisation in the so- tically and leads to the catalytic converter called “low light-off ” direction (low start-up becoming practically 100 % ineffective. Modern engine-management neous mixture distribution operating at systems are able to detect ignition and com.. Operation within a temperature range of 400. hydro- tion is the use of unleaded fuel. The three-way cat- Operating temperature alytic converter’s sensitivity regarding oper- The catalytic converter’s temperature plays a ating temperature limits the choice of instal- decisive role in emission-control efficiency.. absolutely imperative that the three-way stances takes place until temperature exceeds converter is installed close to the engine.1000 °C. a configuration featuring a “pre-cat” At temperatures between 800. possible to comply fully with these operating requirements. “poison” the catalyst and damage it so far Notwithstanding the fact that it is not always that it becomes ineffective. Strict emissions-control legislation demands special concepts for heating the catalytic converter when the engine is started. residual oxygen in the exhaust gas. with carbon monoxide (CO) as the reducing 2. lanthanum. Re- and the carbon monoxide. NOx release takes place as follows. it is impossible The NO2 then reacts with the special oxides for the three-way catalytic converter to com.
An NOx sensor (6) downstream of the tives which are capable of accumulating ox. zirconium. gen that is needed for the oxidation of the Equation 1). This enables the NOx converter carbon monoxide and of the hydrocarbons to accumulate the oxides of nitrogen which is not split off from the oxides of nitrogen have been generated during engine opera- but instead is taken from the high level of tion with excess air.8). Conversion. The more NOx that is stored.g. NOx concentration in the exhaust gas. This leads to the generation of carbon dioxide (CO2) and nitrogen monoxide (NO) (Fig. During lean-burn operation.
Taking the catalyst temperature into ac- verter is similar in design to the conven. barium nitrate Ba(NO3)2 to an ox- ide (e. G. 4). . NOx removal and conversion ium. way converter. Typical accumulator ma. NOx accumulation (storage). In addition to method calculates the quantity of stored the platinum and rhodium coatings. Equa- tion 2). This means that regeneration must on a common substrate. trate (e. Robert Bosch GmbH 80 Catalytic emissions control NOx accumulator-type catalytic converter NOx accumulator-type NOx accumulation (storage) On the surface of the platinum coating. NOx converter continually measures the ides of nitrogen. on the catalyst surface and with oxygen (O2) pletely convert all the oxides of nitrogen to form nitrates. barium oxide BaO). NOx release. the oxy. the engine is run briefly NOx converter operates the same as a three. take place as soon as a given level is ex- ceeded. whereby the following description applies 1. NOx converter is provided with special addi. ous process as it is with the hydrocarbons HC. count (Fig. G. to form barium nitrate (NO3)2 (Fig. the model-based tional three-way converter. Pos. In lean exhaust gases though The processes for releasing the NOx and it also converts the non-reduced oxides of converting it to nitrogen and carbon dioxide nitrogen. For instance. the catalytic converter oxides of nitrogen (NOx) are oxidized cat- Assignment alytically to form nitrogen dioxide (NO2). and agent: The carbon monoxide reduces the ni- 3. due to the noble-metal coating the verted. The NOx accumulator catalytic converter reduces the There are two methods in use to determine oxides of nitrogen in a different manner. H2. and bar. but instead takes duction is slowest with HC and most rapid place in three distinct phases: with H2. 1. NO2 com- (NOx) which have been generated during bines chemically with barium oxide (BaO) combustion. in the rich homogeneous mode (λ < 0. and CO are used as reducing agents.g. when the NOx converter is full and the accu- mulation phase has finished: Design and special coating The NOx accumulator-type catalytic con. the NOx. in other words the accumulated ox- Operating concept ides of nitrogen must be released and con- At λ = 1. This conversion is not a continu. take place separately from each other. the less the The coating for NOx accumulation and for ability to chemically bind further nitrogens the 3-way catalytic converter can be applied of oxide. To this end. terials are the oxides of potassium. In such cases namely. calcium. strontium. over time. the engine can store NOx is highly dependent upon temper. The result is that. 1. phate. therefore. 3). Equation 3). catalytic converter The sulphur in gasoline presents the accu- There are two different methods for deter. (CO). removal phase (2). op- tionally available with integral NOx sensor . 1. Accumulation reaches its maximum mode”. Robert Bosch GmbH Catalytic emissions control NOx accumulator-type catalytic converter 81 between 300 and 400 °C. 6) for NOx accumulation diminishes. G. For instance.a three-way pre- (3) 2 NO + 2 CO ➞ N2 + 2 CO2 cat near the engine (Fig. Barium downstream of the converter measures sulphate is extremely resistant to high tem- the exhaust-gas oxygen concentration and peratures. Pos. and downstream NOX accumulator-type converter and Lambda oxygen sensors Figure 1 1 Engine with EGR 5 6 system 2 Lambda oxygen sen- sor upstream of the catalytic converter 1 3 Three-way catalytic 3 4 converter (pre-cat) 4 Temperature sensor 5 NOx accumulator- type catalytic con- verter (main cat) æ UMA0030Y 2 6 Two-step Lambda oxygen sensor.05) 1 Exhaust-gas system with three-way catalyic converter as pre-cat. the rhodium coating reduces the NOx to nitrogen and carbon dioxide (CO2) Sulphur in the NOx accumulator-type (Fig. For catalytic emissions con- (1) 2 BaO + 4 NO2 + O2 ➞ 2 Ba(NO3)2 trol. eration. The sulphur contained in the ex- haust gas reacts with the barium oxide (ac-
The model-based method calculates the cumulator material) to form barium sul- quantity of NOx still held by the con. which means that G Reaction equations for the NOx accumulation the favorable operating-temperature range is phase (1). be run in the “stratified-charge/cat-heating ature.95) and lean (λ = 1. the verter. When sulphurized gasoline is used therefore. and an NOx accumulator-type main converter (5) Subsequently. and for this reason is only de- outputs a voltage jump from “lean” to graded to a slight degree during NOx regen- “rich” when conversion has finished. Here. selective measures point are applied to heat the converter to between The NOx converter’s ability to accumulate/ 600 and 650 °C. and conversion phase (3) much lower than that of the three-way cat- alytic converter. mulator-type catalytic converter with a mining the end of the NOx-release phase: problem. amount of accumulator material available
A Lambda oxygen sensor (Fig. Rich (λ = 0. two separate catalytic con- (2) Ba(NO3)2 + 3 CO ➞ 3 CO2 + BaO + 2 NO verters must be installed . desulphurization must be carried Operating temperature and installation at regular intervals. Pos. using the carbon monoxide remote from the engine (underfloor cat). on gasoline direct injection with integral NOx sensor) Air Exhaust gas 4 Pre-cat (three-way 1 2 4 5 catalytic converter) 5 Main cat (On mani. the 3b Two-step Lambda located upstream of the pre-cat (4). or Design and construction and low in the lean range (λ > 1). form of control is known as two-sensor con- der that the conversion level for all three trol. This is a measure for the loop control of fuel metering is not accurate composition of the A/F mixture supplied to enough. Pos. Operating concept ture composition with λ = 1. This is always a two-step sensor. the pollutants and it delivers the sensor signal USb. Closed-loop control can also be The sensor voltage USa generated by the two- sensor upstream of used on these systems. This necessitates a stoichiometric A/F-mix. Lambda sensor (two-step control) or a broad-band Lambda sensor (continuous-ac- Lambda control loop tion Lambda control) must be used. two-step Lambda oxygen ensor can only dif- sensor downstream ferentiate between rich and lean A/F mixtures. pollutant constituents is as high as possible. 3a 3b fold injection: three- VE way converter. The barium sulphate (7). on Fuel gasoline direct injec. deviations that the “window” in which the A/F ratio from a specific A/F-ratio can be detected must be located is very narrow. 6 tion: NOx accumula- tor-type converter) 6 Injectors 7 Engine ECU UV USa USb 8 Input signals æ UMK1642-1E US Sensor voltage 7 UV Injector-triggering voltage VE Injected fuel quantity 8 . Since the broad-band Lambda sensor) A Lambda oxygen sensor (Fig. either a two-step reduces to barium oxide as a result. the engine (2). Two-step control 3a Lambda oxygen chiometric. Open. Robert Bosch GmbH 82 Catalytic emissions control Lambda control loop exhaust gases are then passed through the sor signal USa is inputted to the engine ECU cat one after the other. The control principle is based lution is to apply closed-loop control to the on the measurement of the residual oxygen adjustment of the A/F mixture ratio. Figure 1 1 Air-mass meter Direct-injection gasoline engines are run 2 Engine with A/F mixtures which deviate from stoi. The only so. The sen. 1.0. and corrected. in the exhaust gas. 3a) is sensor voltage jumps abruptly at λ = 1. three-way catalytic converter. A fur- ther Lamda oxygen sensor (3b) can be situ- Assignment ated downstream of the main catalytic con- For systems which operate with only a single verter (5). of the main catalytic converter 1 Functional diagram of the Lambda closed-loop control (only if required. In order to do so. step Lambda oxygen sensor upstream of the the pre-cat (two-step pre-cat (4) is high in the rich range (λ < 1) Lambda sensor. which means Using the Lambda control loop. This must be in a state of chemical balance in or. 7. This change is first of all very “sluggish” due to the exhaust gases taking so abrupt.. CO oxidation must take place. such A/F mixtures can also be controlled. the react more quickly to an A/F mixture devia. a stable three-way function is Continuous-action Lambda control needed which provides for a minimum level The broad-band Lambda sensor outputs a of oxygen-accumulation. NOx accumulation and tion (rich/lean shift). λ = 1.3. lean-burn operation. Lambda closed-loop control of gasoline di- Shaping the manipulated variable’s char. Robert Bosch GmbH Catalytic emissions control Lambda control loop 83 The sensor output signal is converted to a Two-sensor control binary signal in the engine ECU and used as When it is situated upstream of the pre-cat. rection changes with each jump of the sen- sor voltage. This means The Lambda sensor upstream of the cat- that not only the Lambda area (rich or lean) alytic converter monitors the stoichiometric can be measured. . from λ = 1 so that the Lambda control can Together with the integrated NOx sensor. while direction. mixture to be closed-loop controlled to val- ues around λ = 1. and this leads to limitations in A/F mixture formation and sets the correct accuracy. The principle of two-sensor high sensor voltage (“rich” A/F mixture). two-step Lambda sensor downstream of the tion. and its control di. part in the two-sensor control but also mon- itors the behaviour of the combination O2 The broad-band Lambda oxygen sensor can and NOx accumulator (detection of the end measure A/F mixtures which deviate from of the NOx release phase). are considerably reduced. The manipulated variable comprises a converter (3b) means that these influences step change and a ramp. With a long to reach it. the control relies upon the upstream sensor manipulated variable adjusts in the “lean” controlling the “lean” and “rich” shift. On the other hand. In addition. sensor downstream of the main catalytic tity. the input signal for the Lambda closed-loop the Lambda oxygen sensor (3a) is heavily control as implemented using software. The control range covers λ = 0. This means that (in contrast to the two-step control). During caused by variations in A/F mixture forma. This leads to better control behaviour NOx accumulator converter not only takes with highly improved dynamic response..0 so that continuous Lambda control is suitable for the “rich” and “lean” operation of engines with gasoline direct in- jection. corrective closed control loop responsible This so-called two-step control enables A/F for additive changes. at λ = 1. rect injection acteristic curve asymmetrically compensates The NOx accumulator-type catalytic con- for the Lambda sensor’s typical false signal verter has two different functions. and for a low sensor voltage the downstream sensor is part of a “slow” (“lean” A/F mixture) in the “rich” direction. In other words. locating the A/F ratio by adapting the injected fuel quan. The stressed by high temperatures and untreated Lambda control has a direct influence on the exhaust gas. but also the deviation composition of the A/F mixture. a jump of the The only problem here though is that a sin- manipulated variable causes the A/F mixture gle downstream sensor would be far too to change. and then it follows a ramp. continuous voltage signal USa. the oxygen required for this afterburning process is available in the In line with present state-of-the-art. the secondary-air pump used for manifold injection can be dis- 2 pensed with. that in those cases in ppm which conventional measures (adjust igni- tion timing in the”retard” direction) do not 300 HC emissions suffice for complying with the stipulated ex- 200 1 haust-gas limits. One method is to adjust the ignition heats up the catalytic converter so that it timing towards “retard”. secondary-air pumps are used for sec- With “rich” A/F mixtures. it is On the one hand. and During the warm-up phase. “lean” A/F mixtures. afterburning also ble. electric exhaust gas in the form of residual oxygen. In the “stratified-charge/cat-heating” operating mode. sions in the first seconds of an emissions ture still present in the exhaust gas are burnt test. quickly reaches its operating temperature. extra air (secondary Ignition timing towards “retard” air) is injected into the exhaust-gas passage In order to keep the pollutant concentration to speed-up the catalytic-converter heating. Robert Bosch GmbH 84 Catalytic emissions control Catalytic-converter heating Catalytic-converter heating for an engine which has not yet reached op- erating temperature. 1 shows the curves of the Secondary-air injection hydrocarbon and carbon monoxide emis- The unburnt components of the A/F mix. an- other method can be used for quickly bring- ing the catalytic converter up to tempera- ppm ture. With tion. This fuel is combusted 2 late and causes considerable heat-up of the 1000 engine’s exhaust side and of the exhaust 0 manifold. this exothermic reaction necessary that the catalytic converter reaches reduces the hydrocarbons and the carbon its operating temperature as soon as possi. Fig. This step lowers the engine efficiency. in the exhaust gas down to a minimum. On the other. with and without secondary-air injec- in the thermal afterburning process. as often needed ondary-air injection. 100 0 km/h Figure 1 50 υ 1 Without secondary- æ UMK1711-1E air injection 0 2 With secondary-air 0 40 80 120 s injection Time n Vehicle speed . This means. that the catalytic converter is quickly ready for operation. monoxide. this process in doing so leads to hotter exhaust gases considerably increases the conversion rate so which then heat-up the converter. during stratified-charge 3000 CO emissions operation with high levels of excess air a sec- ond injection of fuel takes place during the 2000 1 engine’s power cycle. 1 Influence of secondary-air injection on CO and HC Post injection (POI) emissions On gasoline direct-injection engines. 8 Ignition angle. 18 Air charge. 77 Fuel consumption. 67 Ignition driver stage. 36 L Combustion knock. Homogeneous/anti-knock mode. 6 Fuel-supply system. 6 Electronic throttle control (EGAS). 22 Follow-up spark. 62 Fuel-pressure damper. 5 Inductive (coil) ignition system. 36. 72. 26 Camshaft changeover. 44 K Catalytic emissions control. 25 Dual spray. 6 Compression stroke. 4. 49 41 Ignition timing. 65 Homogeneous and stratified-charge NOx emissions. 82 Compression ratio. 25 Injection-orifice plate. 9 Internal EGR. 53 Manifold fuel injection. 66 Inner-gear pump. 73 Air bypass actuator. 77 Displacement-type compressor. 13 Bottom Dead Center (BDC). 56 D High-voltage distribution. 41 Four-stroke principle. 30 Infinitely-variable valve timing. 29 G Low-pressure circuit. 6 Electric fuel pump. 40 Canister-purge valve. 77 Dwell angle. 74 In-tank unit. 39 Continuous-action Lambda control. 75 Air-mass meter. 76 Ignition map. 25 Ignition cable. 24 Broad-band Lambda oxygen sensor. 84 Auto-ignition. 70 N Delivery-quantity control valve. 12 Interference-suppression resistor. Exhaust-gas turbocharging. 46 Lambda closed-loop control. 56 High-voltage generation. NOx accumulator-type catalytic con- Down-sizing. 78 53 High-pressure injectors. 15 Compressor. 33 Carbon canister. 69 Hydrocarbons (HC). 54 M Conversion of toxic components. 26 . 45 Centrifugal turbo-compressor. 29 Exhaust-gas recirculation (EGR). 76 Fuel filter. 27 Homogeneous mode. 15 Electromagnetic fuel injectors. 4 Intercooling. 20 Emission-control legislation. 77 Frictional losses. 76. 46 Knock control. 76 Fuel lines. 36. 42 C Intake manifold. 50 Ignition distributor. 83 Gas-exchange valves. 12 Evaporative-emissions control system. 18. 21 Ignition energy. 55 Fuel-pressure regulator. 45 Lambda oxygen sensor. 48 Cylinder (engine). 5 Induction stroke. 19 Fuel tank. 23 Carbon monoxide. 29 Fuel supply. 14. 73 Exhaust stroke. 36. 25 Catalytic converters. 49 83 External EGR. 30 Injection valves. 19 Excess-air factor (Lambda). 26 Cylinder charge. 67 Gasoline direct injection. 63 Electronic ignition. 58 65 Homogeneous and lean-burn mode. 25 Inert gas. 4 Exhaust-gas turbine. 69 Nitrogen. 50 Externally supplied ignition. 36. 68 A/F-mixture distribution. 65 Non-return valve. 33 65 verter. 18 A EGR valve. 80 Dual injection. 49 Camshaft phase adjustment. 4 Mechanical supercharging. 37. 16. H Monoliths (catalytic converter). 4 Lean-burn limit. 41 Fresh gas. 68 Boost pressure. 19 Dynamic supercharging. 36. 72 Carbon dioxide. 4 B Exhaust valve. 42 Ignition coil. 6 Ignition voltage. 77 Ground electrode (spark plug). 69 A/F ratio. 12 Group fuel injection. 70. Ignition point. 4 Conventional coil ignition (CI). 19 Center electrode (spark plug). 52 mode. 29 Cylinder-individual fuel injection (CIFI). 64 Noble-metal coating. 65 Dual-spark ignition coil. 83 Combustion process. 78 Distributorless semiconductor ignition. 60 Multipoint fuel-injection systems. 71 Manifold chamber. 70 A/F-mixture cloud. 46 Lambda control loop. Robert Bosch GmbH Index of technical terms 85 Index of technical terms Technical terms E I Efficiency. 82 Common Rail. 34 High-pressure pumps. 23 F Intake valve. 37 Lambda. 71 Fuel rail. 72 A/F mixture. 76 Stratified-charge/cat-heating mode. 71 Spark-plug ignition coil. 14 Shunt losses. 42 Torque. 52 Peripheral pump. 52 . 42 Underfloor catalytic converter. 69 Transistorized ignition (TI). 55. 62 Pumping losses. 79 Throttling losses. 59 Two-step Lambda oxygen sensor. 81 76 Swirl air flow. 20 Pre-cat. 52 Tapered spray. 15. 53 Volumetric efficiency. Sulphur charge. 84 Throttle device. 17 Primary winding (ignition coil). 37 P Palladium. 14 S Valve timing. 77 Post injection (POI). 32 Side-channel pump. 33 R Two-sensor control. 17 Single-point injection (TBI). 16 Stoichiometric ratio. 74 Spiral-type supercharger. 74 VST supercharrger. 31 Spark head. 82 Rail-pressure sensor. 56 Two-step control. 6 Overrun. 4 Presupply pump. 7. W 57 Wall film. 78 Three-cylinder high-pressure pump. 64 Static voltage distribution. 57 Positive-displacement pump. 27 Sequential fuel injection. 78 Spark duration. 22 Pressure-control valve. 29 Rotating high-voltage distribution. 52 Operating modes. 64 Oxidation. 62 System pressure. 58 Top Dead Center (TDC). 7 Primary pressure. 69 Spark tail. 75 Spark plug. 70 V Valve overlap. 55. Robert Bosch GmbH 86 Index of technical terms O Spray offset angle. 4 Throttle valve. 83 Ram-tube supercharging. 31 Simultaneous fuel injection. 53 Residual exhaust gas. 53 Single-cylinder high-pressure pump. 9 Tuned-intake-tube charging. 13 Rhodium. 76 65 Oxydation-type catalytic converter. 29 Spray formation. 8 Turbine pump. 17 Stratified-charge mode. 35 Wall wetting. 67 Primary-current limitation. 42 Three-way catalytic converter. 21 Power (combustion) stroke. 83 Rail. 84 Variable intake-manifold geometry. 69 Variable valve timing. 69 Washcoat. 9 Platinum. 78 T Pencil spray. 73 Spark length. 27 p-V diagram. Oxides of nitrogen (NOx). 5 Secondary winding (ignition coil). 79 Rotary-screw supercharger. 43 VTG supercharger. 22 Secondary-air injection. 71 Output power. 78 U Roller-cell pump. 82 Overrun fuel cutoff. 43 Thermal losses. 26 Types of injection. 75 Wastegate supercharger. 17 Stratified charge. 17 Single-spark ignition coil. 76. 56 Trailing throttle. 43 Turbo flat spot. 68 Tumble air flow. Robert Bosch GmbH Index of technical terms Abbreviations 87 Abbreviations R PP: Peripheral Pump A RLFS: Returnless Fuel System ATL: Exhaust-gas turbocharger ROV: Rotating high-voltage distribution B RUV: Static voltage distribution BDC: Bottom Dead Center RZP: Roller-cell pump BPS: Boost-Pressure Sensor S C SEFI: Sequential Fuel Injection CI: Coil Ignition SI: Spark Ignition CIFI: Cylinder-Individual Fuel Injection SRE: Manifold fuel injection CO: Carbon monoxide CO2: Carbon dioxide T TBI: Throttle-Body Injection D TDC: Top Dead Center DI: Direct Injection TI: Transistorized Ignition DR: Pressure regulator V E VST: Variable Sleeve Turbine ECU: Electronic Control Unit VTG: Variable Turbine Geometry EGAS: = ETC VZ: Distributorless ignition EGR: Exhaust-Gas Recirculation EI: Electronic Ignition Z EKP: Electric fuel pump ZP: Inner-gear pump ETC: Electronic Throttle Control EI: Electronic Ignition H HC: Hydrocarbons HDEV: High-pressure injector HDP: High-pressure pump I IV: Intake Valve L LML: Lean Misfire Limit M MPI: Multi-Point Injection MSV: Delivery-quantity control valve N NOx: Oxides of nitrogen P POI: Post injection .