An intake system of an internal combustion engine.

摘要

An engine having a swirl control valve in the intake port. When the engine is operating at a low speed, a lean air-fuel mixture is fed into the engine cylinder, and a swirl control valve is closed in order to create a swirl motion in the combustion chamber. When a predetermined time elapses after the engine operating state is changed from the low speed- light load state to the low speed-heavy load state, the vacuum chamber of an actuator actuating the swirl control valve is opened to the outside air and, thereby, the swirl control valve is forced to open to the maximum extent. At the same time, the air-fuel mixture fed into the engine cylinder is changed to an air-fuel mixture of an approximately stoichiometric air-fuel ratio from the lean air-fuel mixture.