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Research and development activities on high-performance S.I. engines for passenger car application are mainly concentrated on full load performance development as well as the development of combustion systems and engine structures in order to meet future market and legislation requirements. This paper presents results out of AVL's R&D work in the field of multi-valve S.I. engines. Variable Intake Systems of different design are compared to Variable Valve Timing devices with respect to overall engine performance. Engine and vehicle test results of a four-valve engine with the AVL developed C̱ontrolled Ḇurn Ṟate (CBR) combustion system are presented and analyzed. The control of charge stratification, charge motion and hence of the combustion pattern turns out as a major requirement for the investigated advanced combustion systems.

AVL's research work on advanced combustion systems for four-stroke gasoline engines has revealed a strong influence of charge motion and mixture preparation on engine performance, especially exhaust emissions and fuel economy. This paper presents the effects of mixture preparation and charge motion revealed in studies of AVL High Compression Fast Burn (HCFB) combustion systems. Major combustion parameters were investigated and optimized. Control of charge stratification emerged as one of the key elements of advanced combustion systems for both two-valve and four-valve engine configurations. Consequently, measures for charge stratification control are also presented.