Comparison of fuel efficiency and economical speed for internal combustion engine vehicle and battery electric vehicle using backward-looking simulation

A vehicle system-level model is developed to predict economical speed and fuel efficiency of an Internal combustion engine vehicle (ICEV) and Battery electric vehicle (BEV) based on a backward-looking simulation approach. The modeled vehicles were chosen within the same commercial model line-up, sharing body panels and most interior and exterior components, to allow more relevant comparison between different powertrains. Numerical methods were applied to representative engine fuel consumption and standard motor efficiency maps in the process of grid construction and fuel efficiency calculation. The economical speed of each vehicle was obtained for constant speed based on fuel efficiency. Combined fuel efficiency was also predicted considering a 5-cycle calibration using the federal test procedure (FTP-75) and Highway fuel economy test (HWFET). It is found that the calculated vehicle economical speed differs between powertrain configurations. Model results were validated against the certified fuel economy of each vehicle model as well as with the on road driving test results. Parametric studies were performed for varying coefficients of drag force and rolling resistance, gear shifting criterion, and vehicle test weight to analyze economical speed characteristics and the effect of advanced vehicle technologies on overall fuel efficiency. It is shown that the BEVs were more suitable than ICEVs, particularly in low speed range situations, such as urban driving condition in terms of fuel efficiency, and were also more effective when fuel efficiency improving technologies reducing driving resistances were applied.