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The paper presents a GDI concept applied to a four-stroke four-valve single cylinder engine in base of the original “crevice-like” combustion chamber of the basic engine with external mixture formation. For such application both, an adapted shape of injection rate as well as a good correlation of location and timing between injection and spark is requested. The shape of injection rate is adapted in base of a pressure pulse injection system. The paper presents the special features of the system conceived for this aim, as well as the results for different locations of injector and spark plug. The best results in terms of bmep, bsfc and pollutant emissions are obtained with a twin spark configuration. The mixture formation and combustion particularities of this concept are analyzed going from the experimental results at the engine test bench for full and part-load in condition of widely unthrottled operation.

The spray characteristics are determining factors for the quality of mixture formation respectively for the combustion, when applying GDI. Their variation with load and speed is a basic criterion for the adaptability of an injection system type to an engine with known requirements. CFD models of the fluid flow dynamics, mixture formation and combustion are a determining condition for such adaptation. The paper presents the development results of a GDI four-stroke, four-valve, single cylinder engine. The pressure pulse injection system involved in this application is analyzed and presented from the fluid-dynamic behavior up to the obtained injection spray characteristics. The mixture formation and combustion processes are simulated for different load and speed values, respectively for favorable combinations of parameters, such as the injection system configuration, the opening pressure of the applied mechanical injector and the injection duration.