GDI with High-Performance 2-Stroke Application: Concepts, Experiences and Potential for the Future 2004-32-0043

Thanks to its unsurpassed power-to-weight ratio, its low package space and low-maintenance design, the loop-scavenged two-stroke engine with conventional mixture preparation is still being used in some sectors of vehicle engineering, such as boat drives, snow mobiles and motor scooters, as well as in hand-held applications.

To maintain the potential of the 2-stroke engine for the future it is necessary to take adequate steps against the system-dependent disadvantage of the simple 2-stroke engine, namely that of higher emissions compared to 4-stroke engines. One possible solution is gasoline direct injection. Its more frequent use will increase the production numbers, making it an interesting technology even in the above-mentioned cost-sensitive applications.

The current report presents various concepts of direct injection in 2-stroke engines, from air-assisted injection through to high-pressure direct injection, and compares them with traditional techniques of mixture formation. The report describes the experiences with different direct-injection systems, in particular in high-performance engines, from their development up to series application, presenting both simulation results and measurement data from tests for illustration. It also deals with the feasibility of exhaust aftertreatment and with the particularly critical subjective assessment of smoke and smell. In-depth investigations using 3D-CFD were made to develop and examine the different combustion methods and injection systems, including spray and combustion simulations with CFD codes specially adapted for two-stroke engines, taking the movement of the specific two-stroke charge into account. Flow investigations were made to evaluate the simulation and were compared with the tests and the simulations by means of measuring techniques specially adapted for two-stroke engines.

The report concludes with an outlook on the effects of gasoline direct injection on fleet emissions and with the evaluation of future gasoline direct-injection technologies as to their feasibility and potential.