Performance simulations of engine-gearbox combinations for lightweight passenger cars

Abstract

This paper compares the fuel consumption of lightweight passenger cars with three different types of engine (one low speed and one high speed naturally aspirated spark ignited, one turbo-charged compression ignited) and two different types of transmission [continuously variable transmission (CVT) and automated gear drive]. All fuel consumption results are obtained using a quasi-static driving cycle simulator. The implemented models are described in detail. The engines are represented through their eficiency maps, which are obtained by scaling published data. Effciency of the transmission (CVT or gear drive) is modelled in dependence on speed, torque and gear ratio. The simulations show that low fuel consumption can be achieved with all those concepts. CVTs show similar results to automated gear drives. The CVT's theoretical advantage of operating the engine at its most fuel-efficient points is compensated by the relatively low efficiency.