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In the constant development process of modern gasoline engines, the focus is on reducing fuel consumption and pollutant emissions, as well as increasing efficiency. A promising approach is the application of stoichiometric operation in the entire characteristic map. In conventional operation, thermal limitations arise for the components in the exhaust system at high speeds and high specific outputs. At present, additional fuel is injected as a countermeasure because the enthalpy of vaporization leads to a reduction in exhaust gas temperature. This can be also achieved with water injection, together with the reduction of fuel consumption and emissions. The mixture formation with water is of special importance to achieve sufficient cooling and is, therefore, visualized by means of optical measuring technology.

This paper summarises the potential for the use of a gasoline direct injection engine for fuel economy benefits. Various engine technologies are compared for the greatest reduction in fuel consumption at the steady state point 2000rpm/2 bar. This is an important driving point in the EU cycle. The direct injection engine when used in an unthrottled lean stratified mode shows the greatest potential. Calculations show a fuel economy of a middle class vehicle can be increased by 12% using a DI over the EU cycle. The catalytic aftertreatment system is discussed and it is concluded that a close coupled pre-catalyst, a NOx trap and double injection are a good overall solution for the minimisation of exhaust gas emissions from a DI engine.