Development of a Fuel Injected Two-Stroke Gasoline Engine 880170
AVL's development of a semi-direct injected two-stroke engine employed a carburetted 250cc production motorcycle engine as a baseline. Special emphasis vas placed on the investigation of fuel jet and scavenge flow interactions. To evaluate the scavenge flow pattern, a steady flow test procedure was developed and applied. The results of scavenging system optimization were confirmed by subsequent engine tests which showed significant gains in power output.
Completion of the first phase of the research program resulted in the development of a semi-direct injection system using currently available automotive low pressure manifold injection system components. Compared to the original carburetted engine, significant improvanents were demonstrated, including a 30% reduction of fuel consumption, a reduction of up to 60% in hydrocarbon emissions and up to 70% in carbon monoxide emission, averaged over the engine's speed and load range. Engine BMEP and power characteristics were maintained and improved. In addition, the critical idle operating conditions were improved significantly by stabilizing the combustion whith minimized cyclic variations.
The results of thermodynamic cycle analyses, based both on engine test measurements and on calculations, are presented.
Finally, the paper compares the semi-direct and direct injection systems and presents an outlook based on some of the results of the current phase of AVL's low emission two-stroke engine research program.