The investigation was performed by testing into the effects of low pressure(LP) exhaust gas recirculation(EGR) or high pressure(HP) EGR on a gasoline direct injection(GDI) engine and its turbocharger. The behavior changes of the engine and turbocharger with LP EGR or HP EGR were compared at full and partial loads. The reasons of the changes were analyzed through some variations

including combustion

fuel consumption

as well as intake and exhaust. The results indicate that EGR can optimize the combustion of a turbocharged GDI engine

reduce the pumping mean effective pressure and lower the fuel consumption. At partial load

the thermal efficiency with LP EGR is higher than that with HP EGR. The mean reason is that with LP EGR more exhaust energy is applied to turbocharger and the temperature of exhaust gas entering cylinder is lower

thus optimizing combustion.