Exhaust gas recirculation boosted direct injection gasoline engines

Abstract: Downsizing is widely considered to be one promising method for improving the fuel consumption of the spark ignition engine. However, the associated rise in peak in-cylinder pressures and gas temperatures in a unit of high power density can result in an increased tendency to knock. The traditional method to avoid gasoline engine knock involves retarding the spark and/or cooling the mixture with excess fuel. While the regime of fuel enrichment is normally at loads higher than those encountered during existing drive cycle assessments, it is probable that full-load fuel economy targets and emissions legislation will emerge in future years. Various investigations have therefore been made into alternatives to fuel enrichment at high output, and the current chapter is concerned with the benefits and challenges of applying cooled exhaust gas recirculation under such higher loads.