Development of Gasoline Direct Injection Engine 970541
The major problems of the various mixture formation concepts for direct injection gasoline engines that have been proposed up to the present were caused by the difficulties of preparing the mixture with adequate strength at spark plug in wide range of engine operating conditions. Novel combustion control technologies proposed by Mitsubishi is one of the solution for these problems. By adopting upright straight intake ports to generate air tumble, an electromagnetic swirl injector to realize optimized spray dispersion and atomization and a compact piston cavity to maintain charge stratification, it has become possible to achieve super-lean stratified combustion for higher thermal efficiency under partial loads as well as homogeneous combustion to realize higher performance at full loads.
GDI™ (Gasoline Direct Injection) engine adopting these technologies is developed. At partial loads, fuel economy improvement exceeding 30 % is realized. At higher loads, since air cooling by the latent heat of vaporization increases volumetric efficiency and reduces the octane number requirement, a high compression ratio of 12 to 1 can be adopted. As a result, 10% increase in performance is realized. NOx emission had been considered as one of the most significant issues of lean burn engines. This problem is solved by using the inherent characteristics of stratified combustion of high EGR tolerance and by the newly developed lean-NOx catalyst.