In result of the permanent endeavor to reduce fuel consumption of vehicle engines, nowadays the implementation of downsizing concepts is being enforced. Thereby the desired nominal engine power can be produced by an engine with lower displacement operating with correspondingly higher charging pressure. Mechanical supercharging as well as turbocharging can be considered as a suitable supercharging method.

This paper reports on experimental and simulation results regarding the stationary and transient operation of a four-stroke cycle SI passenger car engine supercharged by a new type of screw-type supercharger. In this manner the load control of the SI engine is performed by a supercharger internal slide valve system. Thus not only the throttling losses will be reduced noticeably, but also expansion work can be regained by this supercharger under certain operating conditions. The results obtained will be compared with those of the turbocharged reference engine.

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