Abstract: An internal combustion engine comprising a combustion chamber, an injection chamber connected thereto through an injection port, a secondary inlet passage opening to the injection chamber, and a secondary inlet valve for opening and closing the secondary inlet passage. A spark plug extends into the combustion chamber with the spark gap of the plug close to the injection port. At the suction stroke of the engine, air in the injection chamber is injected near to the spark gap through the injection port to blow away the combustion gas around the gap and also to generate a strong swirl and turbulence of the mixture in the combustion chamber, thereby improving firing and combustion of the lean mixture in the combustion chamber to reduce the discharge of noxious components in the exhaust gas and to improve the fuel consumption.

Abstract: An internal combustion engine comprising a combustion chamber, an injection chamber connected thereto through an injection port, a secondary inlet passage opening to the injection chamber, and a secondary inlet valve for opening and closing the secondary inlet passage. A spark plug is extended into the combustion chamber so as to dispose a spark gap of the plug close to the injection port. At the suction stroke of the engine, air in the injection chamber is injected near to the spark gap through the injection port to blow away the combustion gas around the gap and also to generate a strong swirl and turbulence of the mixture in the combustion chamber, thereby improving firing and combustion of the lean mixture in the combustion chamber to reduce the discharge of noxious components in the exhaust gas and improve the fuel consumption.

Abstract: An internal combustion engine has a combustion chamber which communicates via an injection port with an injection chamber whose volume is 0.5 cc.about.1.5 cc. During the intake stroke, air-fuel mixture is introduced from an intake port into the combustion chamber, and at the same time, under the influence of high vacuum produced in the combustion chamber, a jet stream of exhaust gas, air or air-fuel mixture is violently injected from the injection port into the combustion chamber via an auxiliary intake passage communicates with the injection chamber through an auxiliary intake valve, so that the jet stream enhances the ignitability by scavenging burned gases from around a spark gap and also generates strong swirl and turbulence of air-fuel mixture in the combustion chamber.

Abstract: In an internal combustion engine, an injection hole is provided in the cylinder head to inject narrow streams of air towards the spark gap, particularly during idling and low load running conditions. The injected air is 5 to 30% by weight of the intake fuel-air mixture provided via the intake manifold and creates a swirl or turbulence thereby increasing combustibility. The hole is connected via a sub intake passage to the main air intake passage upstream of the venturi in the carburetor or between the venturi and throttle valve.

Abstract: A crank chamber in a multicylinder-engine is divided by division walls into a plurality of spaces each of which contains one set of cranks fixed to a crankshaft, and in which varying air pressure is developed. The air under such pressure flows into a pressure chamber of an air-pump, as power source to drive the pump; suitably compressed air is produced in a pump chest of this air-pump. This air can be supplied to an exhaust gas passage for recombustion of incompletely oxidized combustive gas in the exhaust gas.