Influence of mixture preparation on HC emission of SI engine with high swirl ratio under cold conditions

Abstract This study investigates the effects of injection timing and fuel atomization on engine-out HC emission of an Sl engine with a high swirl ratio under cold conditions. To study the air-fuel mixture formation process inside the intake port and cylinder, laser visualization techniques were applied and their results were compared with the measured HC emission. Although the performance test indicated that the HC emission deteriorated in the case of one-intake-port operation, the HC emission was recovered by fuel atomization by an air-assisted injector and backflow from the cylinder into the intake port at the beginning of the intake stroke.