Performance and exhaust emissions of a two-stroke spark-ignition engine with a direct-injection system

A direct fuel-injection system has been adapted to a small two-stroke spark-ignition engine to prevent the charge from flowing through the cylinder during the scavenging process. The injection system consists of a jerk-type pump and a single-hole nozzle which supplies gasoline to the cylinder. Engine tests were carried out for comparison with the carbureteur version of the same engine. The results show that the direct-injection version can achieve greatly improved thermal efficiency and lower HC and CO emissions without intake throttling. In addition, NO_x can be reduced to a much lower level than that of the ordinary four-stroke engine. Heat release analysis and high-speed photography indicate that stratified charge combustion takes place in the direct-injection engine.