Abstract: Dynamic control and optimization for the engine with the CVVL system is studied in this paper to solve the problem of acceleration jerk, even engine stall and deceleration speed overshoot after the engine with CVVL is equipped on the vehicle. Engine tests reveal that the root cause of acceleration jerk and deceleration speed overshoot is the different dynamic control behaviors of CVVL system, throttle valve and variable valve timing (VVT) while intake air mass flow of the engine is the dynamic superposition result of the 3 control mechanism. During acceleration, CVVL responses quickly while VVT shows response delay. As a result, the intake air mass flow rises suddenly first and then drops, leading to intake fluctuation and engine jerk. During deceleration, CVVL acts slower than VVT. Intake air mass flow rises suddenly first when VVT is switched and then drops when CVVL goes back to a smaller lift. However, engine jerk during deceleration is not as obvious as acceleration. The problems have been effectively solved and smooth and fast switching at engine dynamic conditions is realized through the introduction of a time filter for CVVL and VVT response speed and the cooperative control of CVVL, VVT and throttle opening angle.

Key words: engine, CVVL system, dynamic operations, control optimization