Development of Small Gasoline Engine with Electronic Variable Valve Timing Unit 2011-32-0579
This paper investigates influences of intake and exhaust valves overlap (at this duration, both of the intake valve and exhaust valve are open) on engine performance. An electric, variable cam phase mechanism (VVT, Variable Valve Timing unit) is installed in a small gasoline engine. The influences on the engine torque and BSFC, Brake Specific Fuel Consumption, are investigated on the engine bench. In addition, in case the overlaps exceeding the experimental range an engine simulator is used to predict the effects.
The experimental results indicate that the VVT system can adjust the target overlap with the accuracy of 1.5deg. in a range of engine speed from 3000rpm to 7000rpm. The response time of the VVT unit was observed at the engine speed of 3000rpm. The results show that the rotation direction of motor affects on the response time of the unit. The measurement of engine torque and BSFC is performed for several overlap values at each engine speed. As a result, by extending overlap using VVT unit, the engine torque can improve in whole range of controllable engine speed in the experiment. The simulation results also predict the possibility of further improvement on engine torque by extending cam overlap.