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In the field of gasoline turbocharged engines, the improvement of combustion efficiency represents a critical point when increased engine torque and reduced fuel consumption are simultaneously expected. Though gasoline port fuel injection is a well known and wide spread technology for fuel delivery in spark-ignition engines, detailed information on the features of the liquid fuel spray and the wall film formation could significantly contribute, in terms of emission control, to the engine development. In this paper, air-fuel mixture formation and smoke emissions of a turbocharged port-fuel-injected gasoline engine have been investigated by using experimental and numerical analysis techniques. The objective of this activity is to properly choose the injection system and strategy aimed to optimize both engine performance and emission levels. 3-D CFD calculations have been performed in order to deeply investigate the complex phenomena occurring before the combustion process starts.

Optimized valve timing, according to engine load, may lead to significant improvements in pumping losses and internal EGR generation. Thus, VVT technology constitutes an effective way to reduce both fuel consumption and pollutant emissions. In this paper, the behavior of a small displacement, 2 valve, Spark-ignition engine, with variable valve timing, has been numerically and experimentally analyzed. The use of VVT allows obtaining combined internal EGR and Reverse Miller Cycle effects so to achieve a significant dethrottling at part load operation. High EGR rates require high turbulence intensity in order to accelerate the combustion rate. The engine performs an accurate combustion chamber design and a tangential intake port able to generate optimized swirl motion, according to the engine speed and load, during both the exhaust gas re-aspiration and the intake stroke. Engine performances at different cam phaser positions have been calculated by means of a 3-D computer code.