The purpose of this study is to verify the effects of a port throttling and 1/4 diagonal port masking of an intake port of an SI engine. The fuel consumption rate increased with port throttling and masking under all operating conditions. However, the rapid combustion effect was increased in all operating conditions. It is consider that this is more influential on the suction resistance than the combustion efficiency increase through intake control. In addition, the increase in the burning velocity indicates that the flame propagation speed is increased by increasing the swirl moment during combustion.

This study was experimentally analyzed to search the swirl characteristics of helical intake port for the performance improvement in direct injection diesel engine. The intake port flow is important factor which has influence on the engine performance because the properties in the injected fuel depend on the combustion characteristics. In order to analyze the characteristics of swirl in the helical intake port of cylinder head, flow coefficient and swirl ratio were measured by an impulse swirl torque meter at position of 1.75 cylinder diameter for different valve lifts at the steady flow condition with intake port of the in-line and V type engine. Each intake ports were established swirl ratio 1.70, 2.13, 2.25, 2.38 and 2.43 by hand working. The results of steady flow test showed that flow coefficient and swirl intensity increased as valve lift increased, while the increase of swirl ratio according to the change of intake port geometry decreased mean flow coefficient and increased Gulf factor.