Predictions of Combustion, Fuel Economy, and Emission Characteristics Influenced by the Gas Exchange Process of S. I. Engines

The conflicting problems of fuel economy and NO_x emissions in a spark ignition engines are discussed in relationship to the residual gas, volumetric efficiency and pumping loss as predicted by the gas exchange analysis which was described in a previous report (SAE P. 800535) . Predictions are made of : (1) the optimum valve timing for obtaining maximum volumetric efficiency; (2) the effect of valve timing on the residual gas and intake air charge and their relationships to the power output, fuel economy, and NO emissions; (3) the influence on combustibility and emissions of the main and auxiliary combustion chambers of a stratified charge engine; (4) the effects of the auxiliary intake valve air jet on the combustion of the lean combustion engine; (5) the effect on fuel economy of decreasing the pumping loss by adjusting valve timing and by adding EGR. These applications of the gas exchange calcualtions indicate the importance of the simulation model in evaluating combustibility, fuel economy, and emission characteristics.