Simulation of a transient torque response for engine performance in a spark ignition engine

In the present study, a mean torque predictive model has been proposed and experimentally validated. It includes an inducted air mass model, a fuel delivery model and a mean torque production model. The inducted air mass model and fuel delivery model, considering the dynamic behaviours of air induction and fuel delivery, were proposed to predict the air-fuel ratio excursions under transient conditions. The mean torque production model reflects thermal efficiency, volumetric efficiency, friction and the effect of spark timing. In the spark timing model, knock limit and acceleration retardation are considered. Experiments were carried out to validate the simulation model for step changes of the throttle at constant engine speed. The results show reasonable agreements between simulation and experiment at fully warmed conditions. Using this model, fuelling strategies were varied with open fast throttle while air-fuel ratio excursion and indicated mean effective pressure were predicted.