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The extremely advantageous power-to-weight, respectively power-to-bulk ratio of two-stroke engines in comparison with four-stroke engines are determining arguments for their further application in light powered two-wheelers. On the other hand, the disadvantages of actual two-stroke engines regarding high pollutant emission, respectively high bsfc - in conditions of the drastic limitation of the pollutant level in the next years - will hinder such applications, if a new quality of the two-stroke process cannot be achieved. As demonstrates in numerous research works, the scavenging improvement of a two-stroke engine can lead to a restricted amelioration of these values, but not to another level. The gasoline direct injection is considered to have the highest potential for such development.

The hydrocarbon emission of a two-stroke engine can be partially decreased by scavenging improvement, but emission levels of a four-stroke engine can be achieved only by changing the mixture formation concept, specifically excluding the fuel from the scavenging process. Numerous research projects of gasoline direct injection - from liquid injection to air assisted systems - have been concentrated on two-stroke engines, determining the selection of the concepts which are suitable for series applications. This paper presents such a concept, based on the ram tuned injection: The system is characterized by a pressure modulation which can be adapted for an appropriate injection law, determining a suitable mixture formation for an engine with specific features. This electronically controlled injection system has been developed as a compact low cost unit for application to two-stroke engines with swept volumes of 50 cm3 and 125 cm3 which equip the two-wheeled vehicles.