The application of direct-injection stratified-charge (DISC) engines has been limited by the unsatisfactory atomization performance of existing fuel injectors, although if has great possibilities for improved fuel economy and low emissions through lean combustion. it two-phase injector for DISC engines was developed, which produced a good-quality spray. Injector performance was checked to investigate the spray structure and the optimal conditions in terms of design variables and operating parameters. This air-assisted injector exhibited stable behavior at speeds up to 6000 rpm and produced a finely atomized spray of 14.9 mu m in Sauter mean diameter.