One new cam and three new pistons were designed for a turbocharged gasoline direct injection，(GDI) engine to realize high compression ratio Miller cycle. Moreover

exhaust gas recirculation(EGR) was adopted for the engine. The effects of the Miller cycle of different compression ratios and EGR on engine performance were investigated experimentally. The results show that there is a trade-off between high compression ratio and the Miller cycle in terms of knocking. The fuel consumption of the high compression ratio Miller cycle at low speeds with full load is slightly higher than that of the original engine; while low pressure cooled EGR can apparently improve engine fuel economy at full throttle characteristics conditions due to optimized combustion phase with its dilution and cooling effect. At part loads

the high compression ratio Miller cycle can lower fuel consumption by 6.3%. With low pressure cooled EGR fuel consumption can be further reduced by 3.1%. A conclusion can be drawn: The Miller cycle with a proper compression ratio and a low pressure cooled EGR can greatly improve engine fuel economy.