A simulation analysis for VVA and idle control strategies for a gasoline engine

Automotive idle speed control is a critical issue in engine control fields. Essentially it is a highly nonlinear and time-varying problem. Its performance has a significant impact on fuel economy and emission levels. In this paper, the authors present a complete and coherent engine model, aimed at the challenging purpose of the analysis of the interaction between the idle speed control and variable valve actuation system. The model is based on an innovative approach for engine dynamics conceived mainly on the analogy with electric systems. Firstly, the behavior of a relatively simple and well known control, named Mid-Ranging scheme has been tested on a complete "in-cylinder" engine model, after a modified control is proposed, in order to test the modern engine performances improvement due to the synergy between variable valve actuation devices and idle speed control strategy.