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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.