Advanced Valve ControlSubmitted for MAE 442 (sec 001) Dr. Klang May 4, 2007 Chris Dirito Taylor Hobgood Dawn Glover Outline Valve Basics Advantages of Variable Valve Control Operation Characteristics Types of Variable Valve Control Lift Duration Phase Manufacturers and Examples Future Possibilities Variable Valve Timeline VVT- Variable Valve Timing It can be seen that according to the trend VVT will reach ~ 90 percent of vehicles in 2010 (according to Prof. Dr. Peter Walzer) Throttle Position Broad torque curves are sacrificed . This systems Valvetrain characteristics cannot be changed once the engine is started Limitations: Fuel Economy and Power are only optimized at one particular RPM.Variable Valve Introduction Why Use Variable Valve Timing and Lift? Most basic form of a push rod valvetrain is shown in the adjacent picture. VVT Advantage It can be seen from the graph the increases in torque across the power range of the VVT engine . Maximum at the Cam Nose Typically Specified as Height Valve “Lifts” Away From Valve Seat .Variable Valve Types Valve Lift Specified Amount the Valve Opens to Allow Air and/or Fuel Air Mixture Into Combustion Chamber Controlled by Camshaft Lobe Height. Variable Valve Types Valve Duration Specified Time the Valve is Open Controlled By Camshaft Profile Geometry. Length of Lobe Measured in Degrees of Rotation. Either from Camshaft or Crankshaft . Typically attained by controlling an interface between the timing belt or chain. and the camshaft itself. . Allows for finer tuning of Combustion chamber cross flow.Variable Valve Types Valve Timing Changes Point at which Valve Opening begins with respect to crankshaft position. and coupled with variable ignition timing can be adjusted to increase Combustion Efficiency. .Operation Characteristics Intake Opening Intake valves are opened before TDC (~10-25degrees) Higher engine speed have shorter time for air/fuel ingestion Speeds decrease volumetric flow rate Time delay for valve to open fully At higher engine speeds intake valves must open earlier Higher Intake Closing closed after BDC (~40-50degrees) The intake flow momentum is greater than pressure created by upstroke of piston This momentum is greater at higher engine speeds thus at higher engine speeds intake valve will close later in cycle. .Operation Characteristics (con’t) Valve Overlap Definition: Valve overlap occurs when both intake and exhaust valves are opened At higher engine speeds exhaust from other cylinders in exhaust manifold will pull more air into cylinder Increased speeds valve overlap is desired at higher engine Decreased valve overlap at lower engine speeds increases effective compression ratio which in turn increases torque. Varies duration.Variable Valve Types and Common Manufacturers Valvetronic Offers continuously variable valve timing and valve lift on the intake cam only. BMW VTEC Utilizes two camshaft profiles and electronically selects between the profiles Honda VarioCam Varies intake timing by adjusting the tension of a cam chain Porche AVCS/AVLS AVCS . timing and lift by switching between two different sets of cam lobes Subaru Mitsubishi MIVEC – similar to AVLS . Relies on amount of valve lift to throttle engine BMW VANOS Varies the timing of the valves by moving the position of the camshafts in relation to the drive gear.varies timing (phase) with hydraulic pressure AVLS . Celica •Pontiac . RAV4.Variable Valve Types and Common Manufacturers VVT-i / VVTL-i VVT-i – varies timing of intake valves by adjusting the relationship between camshaft drive and intake camshaft VVTL-i – alters valve lift and timing •Toyota .jp .org/wiki/Image:VVTLi.Avalon. Camry.Vibe VVC Varies timing with eccentric disk Rover Toyota Schematic of VVTL-i http://en.wikipedia. Corolla. . thus high engine speeds are not able to be achieved.Valvetronic Variable Valve Control which uses variable valve Lift (lift can be altered in 300 milliseconds) Under During high loads valve lift will increases low load situations valve lift will decrease Advantages: Fuel consumption reduced by 10 % No need for throttle butterfly (increased throttle response) (Due to no throttle butterfly pumping loss is reduced ) No timing belt or chain required) (Belt/chain only required to spin cam shafts) Disadvantages: Low valve spring rates are required (stepper motor needs to be able to compress valve springs). Valvetronic Simplified Explanation: Valvetronic varies valve lift by adjusting the fulcrum point of the rocker arm. This will influence how much the cam can push down on the valve . The eccentric shaft is turned by an electric stepper motor which is controlled by the engine control unit. com/watch?vrEELtXVTymU .Valvetronic in Action http://youtube. The Mystical Vtec Explained Vtec Variable valve Timing and Electronic lift Control Variable in that two or more camshaft profiles can be utilzed Electronic due to the fact that an electronic solenoid controls the oil flow used to activate and deactivate the system Standard Vtec Varies Valve lift and/or duration by utilizing multiple camshaft profiles. Locking is accomplished with oil pressure and a sliding pin mechanism. System shown varies both valves the same. Advantages are better fuel economy and smoother engine operation at low speeds. while at higher speeds more aggressive camshaft profile allows more power to be utilized. A solenoid triggers at the specified kick-in speed and allows oil flow to the sliding pin mechanism. Desired cam profile is then locked together with the rocker arm controlling the valve on which desired effect is to take place. Both valves are either at low speed profile or high speed profile . Each cam lobe has its own rocker arm. Two Camshaft Profiles can be used. Vtec in Action . Allowing a lean mixture to be used through the one open valve. Interestingly the one closed valve is slightly opened to allow any residual fuel that may pool in the closed intake passage to be used. is purely for efficiency reasons. and decreased emissions. Lean mixture is swirled through the open valve creating a more efficient distribution of the fuel in the combustion chamber. And a standard cam profile is used for the other valve at low rpm and the standard cam profile is used for both valves at higher rpm speeds. Does not create more power. Example Head . but this lift is miniscule.Vtec-e Vtec-e Vtec system where a extremely low cam profile is used at low rpm for one valve. increased engine efficiency. Leads to increased fuel mileage. This effectively closes one valve on a 16 valve cylinder head. usually on the highest lift profile. In the illustration below the three significant camshaft profiles can be seen. is not attached to a valve so that the highest lift is only used when the system is in operational Vtec range. This system operates like Vtec-e closing one valve at low speeds and then opening both valves at a standard lift and duration at a midrange rpm. Utilizes 3 separate Camshaft Profiles.3 Stage Vtec 3 Stage Vtec Vtec system which combines the standard Vtec and Vtec-e concepts to create a high power. Like standard Vtec one rocker arm. fuel efficient valvetrain. And the sliding pins for each stage are shown as well . It then has a high rpm cam which opens both valves aggressively as in standard Vtec. Typical System Typically phase angle is adjusted with oil pressure radially.Vanos Valve Timing Control Method of adjusting cam sprocket relation to camshaft position. Allows for advanced or retarded valve timing to be used. Double Vanos controls both intake and exhaust camshafts . Most Japanese and American Manufacturers use this method. Vanos BMW utilizes Vanos which adjusts relation between camshaft and sprocket by using two concentric pitched gears. This allows for more precise movement. A oil fed cup pushes one sprocket through the other axially thereby adjusting their relative phase angle. Oil Flow is Controlled by electronic solenoid. and a more controllably linear motion as opposed to the radial motion of other systems. Usually only intake camshaft is adjusted. Angle is adjusted using oil pressure as in Vanos but is actuated in a rotational method.Other Phase Changers i-Vtec Utilizes Oil actuated cam sprocket and follower. as opposed to BMW’s linear actuation. Oil pressure controlled with electronic solenoid Typically Other manufacturers use similar technology . . This is housed in a rotating housing. allowing for camshaft lift to be mechanically adjusted from no lift to maximum lift.Japanese Continuous Lift Modification A-Vtec Stands For Advanced Vtec Utilises a Intermediate Rocker Arm between the Camshaft and the Valve Rocker. whatever You think is right. Not just what the Pros think is right. This allows for updates to be implemented without major tear down and rebuild. Either directly by solenoids or stators. In car capabilities A laptop with correct software can be used to continuously analyze engine performance.Aftermarket Adjustments Infinite Adjustability Almost all systems controlled electronically. Allows for changes to be made on site to experiment with the most useful settings without extensive R&D. Benefits Can readily change engine tuning from a useful efficient street setting to an aggressive racing setting at the push of a button. Personalized Engine performance. Ignition Timing and Phase Timing can be measured and changed to optimize performance. These electronic components can be tapped into and controlled by remappable software. Multi-stage systems such as Vtec can be changed to engage at different RPM settings. or by electronically actuated oil flow. . Future Pneumatic Valves The valve spring pocket is replaced with a chamber pressurized with a gas (usually nitrogen because it is less temperature-sensitive than O2) Still use traditional camshafts The system has been used in Formula 1 racing since 1980s Allows higher RPMs – valve springs have to be very stiff to allow high RPMs which creates more engine drag and slower valve timing . Solenoids accomplish this either directly or through electromechanical or electro-hydraulic connections.Future Electrical Solenoids Presently only used in the most modern systems Open and close valves without using valve springs as the main mode of valve closer. duration. and lift Drawback – large size of components may be impractical for some vehicles with standard 12-volt system Instead – can use 42-volt electrical system with smaller components which also eliminates camshafts and thus reduces engine friction and increases mechanical efficiency . Soft closings – less destructive force can allow for use of ceramic valves which can withstand higher temperatures Can potentially have infinite variability in controlling valve timing. Future Camless Valve Actuation . the magnetic field collapses and the spring expands and shuts the valve . the spring collapses and the valve opens 4. Current flows through the coil and a magnetic field forms around the coil 2.Future Solenoids – Camless Valve Actuation 1. The magnetic field attracts the armature toward the center of the coil 3. As the armature moves upward. When current stops flowing to the coil. htm •US Patent # 6.819 •Honda Worldwide. http://world. 1 May 2007 http://www.bmw. 4 May 2007. http://www.com/motorcycle-technology/vtec/img/p3_04. 1 May 2007. 1 May 2007.dk/teknisk/en_artikkel. USPTO.819. 2005.luk-korbmacher. 4 May 2007.honda. http://www. http://www.htm&r=1&f=G&l=50&s1=6.com/watch?v=rEELtXVTymU .org/technical_school/engine/vvt_2.jpg •VTEC. 2003.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1 &u=%2Fnetahtml%2FPTO%2Fsrchnum.819&RS=PN/6.autozine. 3 May 2007.de/Autos/Technik/vtec.968.asp?id=5 •Different Types of VVT.uspto. 1 May 2007. 2007.com/manufacturers/auto/powertrain/gas/valvetrain/vcp/ •VANOS.htm Valvetronic. http://youtube.968 .References: •Delphi Variable Cam Phasers.&OS=PN/6. 2007.968.delphi. 2006. http://patft. •BMW 2004.819.PN.968. Inc. 2004 •BMW World. 2002 http://www. 2 May 2007.fordmuscle. Dr.com/data/documents/spectrum20.gif > •Prof.bmwworld. 2007. 2005.References: •Hope A. Pulkrabek. Technology Highlights and R and D Activities.pdf .com/fundamentals/pistontovalve/images/overlap. Peter Walzer. Bolton and Jay M.<http://www. < http://www. Valvetrain System Design and Materials . OH. Larson.com/technology/valvetronic.htm > •Ford Muscle.fev. 2nd Edition.gif> •Honda Engines. Engineering Fundamentals of the Internal Combustion Engine. 2 May 2007. 1997 •Willard W. Pearson Education.com/en/images/249. NJ.honda-engineseu. <http://www. 2004. 1 May 2007. Materials Park. 2007.htm> Smart Valve Actuation: The Camless Engine Becomes a Reality.org/wiki/Variable_valve_timing> RACER MAGAZINE: F1 Engine Power Secrets. 2007.com/hydraulic/electric_solenoid_actuator. 2006.motorcycledaily. The Sportbike Engine of the Future: Other Valvetrain Options. 3 May 2007.com/12february06_valves. <http://en.valeo.engineersedge.References Wikipedia: Variable Valve Timing. 3 May 2007.com/ferrari/f1engine/> Motorcycle Daily. 1 May 2007.htm> . 2000. <http://www.com/automotive-supplier/Jahia/lang/en/pid/1317> Engineers Edge.wikipedia. 3 May 2007. <http://www. 2005. 3 May 2007. <http://www. <http://www.pureluckdesign.