JPS6218732B

PURPOSE:To assist in generating turbulent gas flow and improve combustion especially during low load, by providing in an exhaust system a means to generate turbulent flow by combustion gas flowing back to the combustion chamber and at the same time providing in an intake system a means to generate turbulence by intake gas. CONSTITUTION:In the beginning stage of a suction stroke already combusted gas flows back from an exhaust valve 13 that is not completely closed, and at the same time intake gas advances into the combustion chamber 4 from an intake valve 12. Guide walls 14 and 19 which generate rotating currents project from one section around an exhaust valve port 6 and intake valve port 5. The exhaust gas and intake gas gather in the same direction and become powerful rotating currents, because of the difference of fluid flow resistances through the passage in which the guide wall exists and the passage without it, and they flow in the combustion chamber 4. Accordingly, the combustion flame growth becomes strong and certain without changing air-fuel ratio, and combustion of all the suction gas mixture can be assured even when low load operation in which the proportion of new air-fuel mixture is small.