Study on improvement of fuel economy and reduction in emissions for stoichiometric gasoline engines

This paper presents the experimental study results carried out on an electronically controlled fuel injection ‘stoichiometric gasoline engine’ by using cold EGR and increasing ‘compression ratio’ to improve fuel economy and reduce emissions. After the compression ratio of the engine is raised from 8 to 11.8, and EGR rate and air swirl ratio are optimized, the fuel economy is improved by 6.02%, and the NOx and (NOx + HC) emissions are decreased by 52.96% and 44.94%, respectively at full-load speed characteristics. The calculation results of heat release rates according to the measured indicator diagram show that the combustion process is remarkably improved.