Internal combustion engine cylinder head variable swirl siamese type intake port structure, with auxiliary straight passage, pointing at spark plug, leading from mixture intake to downstream end of straight intake port

Abstract

A variable swirl siamese type intake port structure for an internal combustion engine cylinder head includes a first generally straight intake passage which leads to a first intake port and a second generally helical intake passage which leads to a second intake port which is formed with a helical end vortex portion. A control valve is fitted in the first generally straight intake passage at an upstream portion thereof so as to control its flow resistance. A substantially straight auxiliary passage, opening from a point upstream of the control valve to a point near the downstream end of the first intake port and bypassing the control valve, points through the first intake port, when open, generally at the ignition point of the engine spark plug. Thereby, when the control valve is closed, even then an air-fuel mixture stream is directed straight at the spark plug, and this prevents local weakening of mixture due to centrifugal effects. Thus good ignition characteristics are obtained, the limit for weakening the air-fuel mixture can be extended, and the engine volumetric efficiency and the maximum attainable engine output power are increased.

Dependencies are inferred from the claim text.