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This paper deals with an investigation of the scavenging and power performances of a two-stroke cycle gasoline engine having poppet valves in the cylinder head but no cylinder ports. In a previous experiment, a model test apparatus was used to carry out the experimental analysis of scavenging performance. We found as a result of this analysis that better scavenging efficiency could be obtained by improving the flow pattern of scavenging gas in the cylinder by means of scavenging valves with shroud than by perfect diffusion scavenging. The present experimental study using a real engine was conducted according to this finding. The basic engine is a four-stroke motorcycle engine, one cylinder, 250 cm3, twin-cam, four-valve. The engine was modified into a two-stroke cycle engine by altering the camshafts so as to have twice the engine speed of the four-stroke cycle engine, and the valve timings were adjusted by a pin that connected the camshaft and sprocket.

This paper analyzes quantitatively mechanisms and its effects of reducing simultaneously NOx/fuel-consumption taking the focus on torch-jet lean combustion control modeling in a pre-chamber type stratified-charge approach with actual Honda CVCC engine test examples. For analyzing the NO x /fuel consumption reduction mechanism and effects, so-called phenomenological modeling centering around torch-flame-jet behavior are examined with varying the design factors such as auxiliary chamber volume/torch nozzle area. Then, main physical features and those characteristics of torch-flame-jet such as the combustion pressure rise histories in pre-chamber, penetration length/volume/speed of torch-jet in lean mixture of main chamber, lean mixture shear-flow entrainment and turbulence enhancing effects induced by torch-jet are computed with numerical methods and those various effects for the lean ignition/combustion are examined.