Efficiency scaling method of gasoline engines for different geometries and the application in hybrid vehicle simulation

This work presents a scalable model of a naturally aspirated gasoline engine forecasting the effective efficiency map for varying cylinder displacements. Engine test bench measurements and a global nonlinear hybrid optimization method were used to calibrate the engine model. The validation showed a good prediction of engine efficiency by the scaling model with a mean error of 2% compared with the measurements. A pure scaling of the cylinder displacement led to overall small changes in the effective engine efficiency map. In addition to the development of a scalable engine model, a forward-looking hybrid vehicle simulation model was used in order to evaluate the impact of different engine cylinder displacements on fuel consumption. For this purpose, simulations for varying cylinder displacements were performed in a series–parallel hybrid drivetrain of an A-class vehicle in two driving cycles. The simulation results showed a small influence of different engine cylinder displacements on fuel consumption for the given configuration.