Higher thermal efficiency and reduced combustion gas temperature are essential requirements for improved fuel economy and reduced NOx emissions of the indirect injection (IDI) diesel engine for passenger car.
The authors have successfully developed a new combustion system, of which main elements are combustion chambers of new design, electronic EGR system and needle-roller rocker arms, and is currently incorporated in Mitsubishi 4D65 diesel engine (swirl chamber system and four cylinders of 80.6mm bore and 88mm stroke each).
The new combustion chamber has such design features as a refined jet-passage where the optimum air-discharge coefficient as well as improved diffusion and penetration of the jet into the main-chamber are available, high compression ratio, enlarged jet-passage area and redesigned piston cavity and has improved to get optimum EGR ratio at different driving condition. Also, needle-roller type rocker arms are used in the engine to reduce the friction loss.
The test results of the engine with the new systems have proven much improvements in terms of fuel economy, NOx and smoke emissions, etc.