Development of a Direct Injection Concept for Two Wheelers Equipped with Two Stroke Engines 1999-01-1248

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. Going from the advantageous spray characteristics of the system, a new combustion chamber has been designed. The engine results show that the engine torque remains in all of the speed range at least at the same level as for the base engines equipped with carburetors, while the bsfc decreases generally 35…45%. But the most important result is the reduction of pollution - with 80…94% for the HC Emissions and 90% for the CO Emissions respectively.