Advanced Downsized SI Engine Operation
Engine downsizing is widely adopted to improve the fuel economy of gasoline engine powered passenger cars, which involves the replacement of a naturally aspirated PFI gasoline engine with a smaller boosted DI gasoline engines. In order to maximize the fuel economy of a downsized engine, it is necessary to reduce further the pumping losses at part-load and minimise knocking or low-speed preignition at high load. This project investigate the application of Miller Cycle to the highly downsized direct injection (DI) gasoline engine. The effects of Miller cycle on the emissions, thermal efficiency and performance were carried out in a single cylinder DI gasoline engine of 120kW/l on a dedicated transient engine testbed with the boost pressure up to 5 bar provided by an external compressor. In addition the use of combined PFI and DI fuel injections on the engine performance and emissions are being studied.