Research on Reduction of Fuel Efficiency Based on Hydraulic Variable Valve Mechanism of Four-Cylinder Engine

A hydraulic variable valve mechanism based on four-cylinder gasoline engine is developed independently, which can realize continuous variable valve lift and closing time. From the perspective of the average turbulent kinetic energy in the cylinder, the pressure in the cylinder, the ignition delay period and the combustion duration, the fuel economy of the throttle control strategy (TH), the early intake valve closed control strategy (EIVC) and the intake valve and throttle synergy control strategy (IVTS) are analyzed. The results show that the fuel economy of EIVC control strategy is 9.4% lower than that of TH control strategy (original engine) at medium and small loads. With the increase of load, the improvement effect of EIVC fuel economy gradually decreases. Different cycle cylinder deactivation rates (20%, 40%, 50%) are suitable for use in medium and small load working ranges, and the greater the cylinder deactivation rate, the better the fuel economy improvement. The 50% cylinder deactivation rate can save fuel by 13.1% compared with the TH control strategy. In the case of large load, the EIVC control strategy is optimal. Under various operating conditions, the fuel economy of IVTS control strategy is between that of EIVC control strategy and TH control strategy.