Analytical Evaluation of Engine and Vehicle Hardware Effects on Vehicle Response 2019-01-1283
As the proliferation of downsized boosted engines continues, it becomes increasingly important to understand how engine hardware impacts vehicle transient response. Currently, a constant speed load step is used to evaluate the transient response of an engine. This load step is sufficient for A to B hardware comparisons and can help guide transient response in the right direction, but it does not represent a real vehicle condition and can potentially lead to focusing on the wrong hardware to optimize vehicle transient response. The next evolution of predicting engine transient response is to transition to a system level analysis by coupling a detailed engine model, utilizing crank angle resolve calculations, with a simple vehicle model. This allows for the evaluation of engine hardware effects on vehicle acceleration and the rate of change of vehicle acceleration, or jerk, and the trade-offs that can be made with vehicle hardware. By completing this evaluation for several different hardware sets, it can be shown that the best hardware set for a constant speed load step does not necessarily translate to the best hardware set for vehicle transient response. From this system level analysis a greater understanding of engine hardware effects on vehicle transient response can be gained, which allows for improved optimization of vehicle level response, performance and fuel economy.