Analytical Evaluation of Engine and Vehicle Hardware Effects on Vehicle Response
To be published on April 2, 2019 by SAE International in United States
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.