The effect of intake valve lift load control on gasoline engine fuel economy

The conventional SI engine with throttle-driven load control, has a disadvantage in fuel economy dominantly caused by its pumping loss. In the paper, throttle-free load control strategy, namely the application of valve lift adjustment and phase optimization, was employed to reduce the pumping loss and improve the fuel economy. Tests were carried out on a single-cylinder research engine equipped with 4WAS(4 Variable Valve Actuation System) cylinder head, which can independently control the intake and exhaust valve lifts and timings. Results show that pumping loss can be reduced 20~30% by using the valve lift load control, and a 3~12% of fuel consumption benefit can be obtained.