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The startability of SI engines, especially of DISI engines, is the greatest challenge when using ethanol blended fuels. The development of a suitable injection strategy is therefore the main engineering target when developing an ethanol engine with direct injection. In order to limit the test efforts of such a program, a vaporization model has been created that provides the quantity of vaporized fuel depending on pressure and on start and end, respectively number and split relation of injections. This model takes account of the most relevant fuel properties such as density, surface tension and viscosity. It also considers the interaction of the spray with cylinder liner, cylinder head and piston. A comparison with test results shows the current status and the need for action of this simulation model.

This paper describes the operation and performance of two direct fuel injection strategies, namely a ram-tuned injection system (single fluid) and an air-assisted injection system (twin fluid). The injection systems are tested on a 500 cm3 single-cylinder cross scavenged two-stroke cycle engine during part load operation at 1600 rev/min. Particle sizing tests are presented for each injection system, in conjunction with specific emissions and performance results for firing engine tests.