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A full 3D Large Eddy Simulation (LES) of a four-stroke, four-cylinder engine, performed with the AVBP-LES code, is presented in this paper. The drive for substantial CO₂ reductions in gasoline engines in the light of the global energy crisis and environmental awareness has increased research into gasoline engines and increased fuel efficiencies. Precise prediction of aerodynamics, mixing, combustion and pollutant formation are required so that CFD may actively contribute to the improvement/optimization of combustion chamber, intake/exhaust ducts and manifold shapes and volumes which all contribute to the global performance and efficiency of an engine. One way to improve engine efficiency is to reduce the cycle-to-cycle variability, through an improved understanding of their sources and effects. The conventional RANS approach does not allow addressing non-cyclic phenomena as it aims to compute the average cycle.

The drive for substantial CO2 reductions in gasoline engines in the light of the Kyoto Protocol and higher fuel efficiencies has increased research on downsized, turbocharged engines. Via a higher intake air pressure, an increase in specific power output can be reached on a comparatively smaller sized engine, in order to ensure high torque capabilities, while allowing a fuel saving of about 20%. This fuel efficiency benefit includes the advantages of direct injection (DI) technology which avoids crossflow of fuel. This paper presents the capabilities of Computational Fluid Dynamics to aid in the development of such engines. Particularly, the IFP-C3D code offers several recently developed models which permit to estimate, with good accuracy, the evolution of the combustion under given working conditions. Moreover, the capability of the model to predict knock occurrence is very helpful for engine designers within the framework of development of new downsized turbocharged engines.