Abstract
The performance of a spark ignited, direct fuel injection (DI) engine is investigated. We considered the injector layout, placing it in the center of the combustion chamber with the spark plug. Different combinations of injector and piston shapes were examined. The DI engine with a cavity piston, 2 valves, helical port, 4 strokes and 1 cylinder can get homogeneous and stratified charges by just changing the fuel injection timing and fuel amount. We measured the exhaust gas characteristics. The bigger the air-fuel ratio is, the lower the HC and NO emissions and the fuel consumption are. We also examined a DI engine with a flat piston, 4 valves, pent-roof chamber, 4 strokes and 4 cylinders. Its performance is close to that of the current port injected engine.