Abstract: Exhaust gas temperature is raised after a cold engine start so as to rapidly activate a catalyst in an exhaust line by retarding an ignition timing at which an air-fuel mixture is fired in the engine to a point after top-dead-center during a certain time interval and promoting combustion of the air-fuel mixture, thereby accelerating the catalyst to attain its effective activation temperature after the cold engine start as quickly as possibly.

Abstract: An engine intake system includes a primary port for introducing intake gas throughout an entire engine operating condition. A secondary port is provided with a gate valve which is opened in a high engine load condition for introducing the intake gas. A ratio of a tumble flow to a swirl flow is gradually increased as the gate valve is operated from an entirely closed condition to a fully open condition. According to this invention, ignition and combustion characteristics can be improved.

Abstract: A fuel injection system of an internal combustion engine including air introducing passage device extending in one direction for introducing auxiliary air under pressure, annular fuel passage of a disc-like space extending radially outwardly from the air introducing means and substantially perpendicularly to the air introducing passage for introducing fuel for combustion, annular opening provided at inner end of the annular fuel passage for injecting the fuel into the auxiliary air flowing in the air introducing passage from position surrounding the auxiliary air flow at a right angle to the flowing direction of the auxiliary air so that the fuel is atomized to be mixed with the auxiliary air. The fuel from the fuel injecting means is substantially perpendicularly injected into the auxiliary air flow in the form of a thin membrane so that the atomization of the fuel can be effectively facilitated resulting in an improved combustion performance of the liquid fuel.

Abstract: An internal combustion engine is provided with a fuel injection valve in an intake passage communicated with a combustion chamber and a swirl controlling device for controlling a swirling motion to be given to intake air in a circumferential direction of the cylinder forming the combustion chamber. When the engine load is low, the fuel injection valve is controlled to inject fuel by an amount required for one power stroke a predetermined time after the intake valve is opened and during the intake stroke, and the swirl controlling device is controlled to give intake air a swirling motion. A correction device is provided, which, when the engine is cold, controls the fuel injection valve to start fuel injection before the intake valve is opened and also controls the swirl controlling device to suppress production of swirling motion of intake air.

Abstract: The air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine is determined on the basis of a smoothed amount of intake air and a smoothed throttle opening. The smoothed amount of intake air is reflected by a predetermined ratio of a former amount of intake air to the newest amount of intake air. The smoothed throttle opening is reflected by a ratio of a former throttle opening to the newest throttle opening substantially identical to said predetermined ratio.

Abstract: An intake system for an internal combustion engine comprises a first valve provided to open and close an intake passage leading to each combustion chamber, a bypass passage for introducing intake air into each combustion chamber bypassing the first valve, and a second valve provided to open and close each of the bypass passages. The first valves are operated to close the respective intake passages in a light load range and to open the same in a heavy load range. The second valve is operated to close the bypass passage in the middle of each intake stroke. The first valves are controlled so that the opening of the intake passages is increased as the engine load increases after exceeding a predetermined value, and the second valve is controlled to delay the time the bypass passage is closed with increase in the engine load so that the time the bypass passage is opened overlaps with the time the intake valve is opened when the engine load reaches the predetermined value.

Abstract: The combustion chamber for an internal combustion engine is formed by a main combustion chamber defined by a recess formed in a part of the lower face of a cylinder head and a squish zone which is a narrow space formed between the top surface of the piston in the top dead center and the substantially flat portion of the lower surface of the cylinder head around the recess. A spark plug is disposed in a position near the squish zone. A fuel injection valve is provided to inject fuel into an intake passage communicated with the combustion chamber by way of an intake valve. The fuel injection valve is controlled, at least when the engine load is low, to inject fuel by an amount required for one power stroke and to terminate fuel injection before the middle of the intake valve opening time at latest so that stratification of air and fuel can be obtained in which rich mixture is accumulated in the lower portion of the combustion chamber and lean mixture in the upper portion of the same.