. It is evident from Fig.7 that the variation in combustion efficiency (η) with 4 sburn time is small. The reason for this might be that as the L⋆ increases ,the residence time is increasedas the flow velocities in the port are reduced (dp increases). Also, the radial distance between the reaction zone which is close to fuel surface and the port axis increases. This is the distance that the hot product gases need to diffuse. Thus, the net effect is nearly the same as it was at the start of