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Four ports which have slightly different shapes have been applied to 3-valve MPI SI engine to develop Axially Stratified Lean Combustion engine. The purpose of port modification test was to investigate the effects of swirl ratio and direction on engine performance and emissions. In the engine test injection characteristics, i.e. timing, flow rate, direction as well as port design significantly effected on the engine combustion. Especially, it was observed that injection timing was the most important factor for combustion stability, but its effect on performance has some differences in accordance with the port designs. To verify the relationship between port shape and injection timing, in-cylinder gas was sampled by high speed gas sampling device varing injection timing through whole intake and compression,. strokes at spark plug position and analyzed by gas chromatography.