Internal combustion engine with dual induction system

Abstract

A spark ignition reciprocatory internal combustion engine with dual induction system is provided which has within a cylinder head a primary induction passage or a primary intake port passage to direct fluid charge into a cylinder to swirl therein and a secondary induction passage or a secondary intake port passage to direct fluid charge into the cylinder in such a direction as to impeded and reduce the swirling motion of the first fluid charge to provide a low 'swirl ratio' within the cylinder, thereby to maintain the volumetric efficiency of the engine at a sufficiently high level. A primary throttle valve is provided to control the quantity of fluid charge entering into the primary induction passage and a secondary throttle valve is provided to control the quantity of fluid charge entering into the secondary induction passage. The secondary throttle valve is coordinated with the primary throttle valve so that the secondary throttle valve will remain closed until the primary throttle valve opens wider than a predetermined opening degree. Under engine operating conditions when only the primary throttle valve opens, fluid charge from the primary induction passage will swirl at a high 'swirl ratio' in the range of 1.5 to 6, while, under engine operating conditions when both the primary and secondary throttle valves open, fluid charge from the secondary induction passage will impede swirling motion of fluid charge from the primary induction passage to provide a low 'swirl ratio' in the range of 0.5 to 1 within the cylinder, and to maintain a high volumetric efficiency of the engine.