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Variable Valve Timing

Variable Valve Timing. Investigation by Katie James Advised by Professor Bruno & Professor Krouglicof. Variable Valve Timing (VVT) Use In Internal Combustion Engines. Arising Constraints Impose New Standards The Evolving IC Engine Current Advancements and Developments

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Variable Valve Timing

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  1. Variable Valve Timing Investigation by Katie James Advised by Professor Bruno & Professor Krouglicof

  2. Variable Valve Timing (VVT) Use In Internal Combustion Engines • Arising Constraints Impose New Standards • The Evolving IC Engine • Current Advancements and Developments • Future Applications • Progressive Intellectual Capital at Union

  3. Spark-Ignition Focus Many factors have steered commercial market away from standard IC-engine with spark-ignition • Growing competition from alternative power sources • More efficient fuel consumption due to heightened emission restrictions • Individual company commitments toward higher performance demands and safety regulations without compromising comfort level or retail value

  4. Effects of Reduced Fuel Consumption • Pumping losses • Combustion efficiency • Minimal friction from Direct Injection • Downsizing • Higher pressure charging

  5. Thermodynamic Solutions • Thermodynamic conditions must operate at higher loads • Or reduce gas exchange/heat loss at part load • Supercharging • Turbo-charging • Fully Variable Valve Timing • Direct-Injection

  6. Current Design: Delphi Automotive Systems Cylinder Deactivation System Enables cut-out of half cylinder count to boost fuel economy. • Intake stroke of exhaust valves are disabled with target cylinders using oil pressure or electric solenoids • Simultaneously FI is cut off to target cylinders • “Forward-tumble Direct-Injection”- A/F mixture stabilized near ignition source zone • Produces 8 to 10% decrease in emission levels.

  7. Current Design: Motronic D-I System VW Golf 1.6L Direct-Injection SI Engine Generates pressure in full rail that supplies electromagnetically controlled injector with gasoline. Fuel quantity is controlled and adjusted to intake-air mass using information from wide-band oxygen sensor.

  8. Variable Valve Timing VVT avoids exchange losses due to charging. • Electromechanical valve train surpasses improvements made by port-fuel-injected gasoline engines because variability allows for precise air/fuel intake.

  9. Current VVT Design: Siemens VDO • Variable Valve Lift Control (LVC) • Elimination of throttle valve • Able to restore energy lost due to gas exchange work normally performed by throttle valve • Gas exchange directly controlled by intake valve • Variability provided using electromagnets • Allowing valve timing to be infinitely (fully) adjustable ** • Reducing fuel consumption up to 10%

  10. Current VVT Design: i-VTEC by Honda New “intelligent” valve control adding Variable Timing Control (VTC) • Continuously adjusts camshaft phase to both VVT and lift electronic control on intake valves • Varies lift and actuation time of intake opening: • Adjusts optimal cylinder filling in low rpm settings; staggered valve timing and asymmetrical lift • Impressive high rpm power output • Performs continuously variable camshaft “phasing” across entire engine band • VTC actuation controlled by cam position, ignition, exhaust and throttle position

  11. Additional VVT Design Highlights • BMW goes throttleless with Valvetronic • Infinitely adjusts intake valve lift • First production gasoline unit without throttle butterfly • 85kW engine consumes 1.8gal in 62mi (0.2gal reduction) • Transition from carburetors to fuel injection, from two to four valve technology, and mechanical to electrical engine management

  12. Additional VVT Design Highlights • Bugatti incorporates VVT into two V8 cylinder blocks • 64 valves operated by overhead camshafts cia electrohydraulic continuously variable control system • Coordination of engine handled by two interdependent computers per cylinder bank* • Quad-turbo 16 cylinder power plant yielding highest peak torque in production passenger car

  13. Movement towards Efficiency • Many companies have shifted away from throttle to improve efficiency • Hydraulic actuation and electronic control is incorporated • All available VVT advancements still involve camshaft or rocker arm

  14. One Step Ahead: Progressive Engine Research • Research Test Bed • Take throttleless design • Integrate camless actuation device • replace with electrohydraulic servomechanism • Hydraulic Power Unit • LVDT: Linear Displacement Transducer

  15. Any Questions?

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