Analysis of the combustion process of a spark ignition engine with a variable compression ratio

In the scope of a research program carried out jointly by Volkswagen AG Research, Wolfsburg, and FEV Motorentechnik, Aachen, an advanced engine concept has been developed on the basis of a conventional engine. This concept makes it possible to vary the compression ratio over a useful range by means of an additional chamber in the cylinder head. Extensive investigations were carried out on an engine dynamometer in order to optimize the combustion process. The combustion process was analysed to quantify the losses incurred by various engine and control parameters. This provided control criteria over the entire engine map, making it possible to adjust the compression ratio with respect to optimum efficiency and low emission levels.