Abstract: An exhaust gas recirculating system for a combustion engine has at least one cylinder communicating with a source of combustible air-fuel mixture through at least one intake port adapted to be selectively closed and opened for effecting the interruption and admission of the supply of the combustible mixture into the combustion chamber, the cylinder also communicating with an exhaust system through first and second exhaust ports both adapted to be selectively opened and closed.

Abstract: A part of intake passages is made into an arcuate form extending around a surge tank. A rotatable drum is provided in the surge tank to change the length of the arcuate part of the passages. The rotatable drum is controlled by a control mechanism which is operated in accordance with the engine speed for example, so that the effective length of the intake passages may be changed to keep synchronization between the natural frequency of the intake system and the frequency of the pressure wave caused by the reciprocal motion of the piston of the engine.

Abstract: An internal combustion engine has an air-fuel ratio control system, an exhaust gas recirculation system and an ignition system. At least one of the systems is adjusted when the intake air temperature is very high so that fast combustion is suppressed. The adjustment is effective to prevent detonation or similar unusual combustion which may occur under a very high temperature of the intake air.

Abstract: An air intake system for a supercharged automobile engine comprises a supercharger disposed on an air intake passage, a primary throttle valve disposed in a primary passage downstream of the supercharger and operatively coupled to an accelerator pedal, a secondary throttle valve disposed in a secondary passage and adapted to be controlled in association with the primary throttle valve, an auxiliary throttle valve in the secondary passage upstream of the secondary throttle valve, and an actuator operable to maintain the secondary throttle valve in a full open position when and so long as the load on the engine is equal to or larger than a predetermined medium load and to gradually open the secondary throttle valve with increase of the suction pressure when and so long as the load on the engine is smaller than the predetermined medium load.

Abstract: An internal combustion engine has an exhaust gas recirculation system including a recirculation valve for controlling the amount of exhaust gas returned to the intake system. The position or opening of the valve is controlled to a desired position in accordance with a memory in a memory device storing desired valve positions under various combinations of the engine load and the engine speed. A device is provided for increasing the opening of the recirculation valve when the effective area of the recirculation passage is decreased due to carbon deposits.