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The Two-Stroke engine revival is seen as a way to reduce the size and weight of engines. IFP has been one of the first engine research centres involved since the early eighties in this promising way of a new generation of highly efficient engines. Since this date, a large number of car manufacturers and research laboratories around the world have engaged research and development efforts in this new field. In these conditions, it was essential for IFP to examine the different research works, technological choices, and new ideas. The systematic study of the patents published since 1981 and their statistical analysis represent an interesting tool to follow the main trends of the research in this domain. More than 4200 patents were selected as relevant for this study.

The IAPAC Direct fuel Injection (DI) system, developed by IFP, has already well proven its capability to reduce pollutants emissions and fuel consumption of 2-stroke engine. This crankcase Compressed Air Assisted Fuel Injection Process allowing the introduction of the fuel separately from the scavenging air, minimizes the fuel short-circuiting. In earlier works, results of the implementation of the IAPAC system on cylinder displacement from 125 cc to 400 cc have been presented in various papers. These first prototypes were all using a camshaft to drive the IAPAC DI poppet valve, which was considered as a limitation for applying this system to small displacement 2-stroke engines. The new SCIP system is no more using a camshaft. The IAPAC poppet valve used for low pressure air assisted fuel atomization and in-cylinder injection, is here actuated by a diaphragm and the lift of the valve is controlled by pressures from the engine.