Development, Modeling and Engine Adaptation of a Gasoline Direct Injection System for Scooter Engines 1999-01-3313

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. However, the very short duration of mixture formation after scavenging, as well as the maintenance of sufficient quality of the fuel spray in a wide load and speed range impose an extremely accurate adaptation of the injection system at the engine. For this reason, the possibility of modulation and adaptation of the injection law is of major importance. The paper presents the strategy for the adaptation of an injection system with high-pressure modulation, determining an appropriate injection law, to a compact high-speed two-stroke engine. The adaptation is based on the numerical simulation of the process within the injection system in correlation with the mixture formation process in the combustion chamber. The presentation is focussed on the modeling within the injection system, leading to the appropriate design and parameter combination. Engine tests confirm the effectiveness of this strategy.