Abstract
This paper describes a direct-injection S.I. engine newly developed by Nissan, which attains high power with low fuel consumption and exhaust emissions. The combination of swirl flow and eccentric round bowl-in-piston geometry generates a vertical vortex from the piston bowl to the spark plug, which transports the air-fuel mixture to the spark plug. Fuel consumption is reduced by more than 20%, power output is improved by approximately 10% and the cold-start unburned HC emission peak is completely suppressed. The mixture formation process and soot formation factors at WOT are also analyzed.