Abstract: An internal combustion engine comprises a cylinder and an intake passageway opening into the cylinder. In order to secure sufficiently high volumetric efficiency at high speed under high load operating conditions, the intake passageway is so configured as to pass therethrough a sufficient volume required for the combustible charge to be drawn into the cylinder per unit time. The intake passageway is provided with swirl means for causing the combustible charge passing through the intake passageway to swirl in the cylinder. The swirl means comprises at least one flow restrictor means so arranged as to urge the combustible charge to enter into the cylinder in a tangent direction to the cylinder wall.

Abstract: An automotive internal combustion engine having main and auxiliary combustion chambers for each of the cylinders and combined with a carburetor is provided with an air-fuel mixture induction system which comprises an intake manifold providing communication between the carburetor and each of the main combustion chambers, characterized by passageways leading to the auxiliary combustion chambers and open into the intake manifold or the intake ports for the main combustion chambers through an opening in the main tube portion of the intake manifold, openings respectively formed in the runner portions of the intake manifold or openings formed in wall portions defining the intake ports for the main combustion chambers.