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: An intake system utilizing an air-fuel control which is changed in accordance with the coolant temperature. When the coolant temperature is lower than the first coolant temperature, an open loop control is carried out in accordance with the coolant temperature so that a fluctuation of the air-fuel ratio can be restricted so as to obtain a stability. An air-fuel feedback control is carried out between the first and second coolant temperatures wherein the air-fuel ratio is maintained at the stoichiometric value so that an increase of NO.sub.X emitted from the engine can be suppressed. In the region in which the coolant temperature exceeds the second temperature, an air-fuel feedback control is carried out in the lean mixture side of the stoichiometric value in accordance with the coolant temperature to thereby improve the emission performance of the engine.

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: A throttle valve control system comprises an accelerator position sensor for detecting the amount of operation of the accelerator, a throttle valve opening degree determining circuit which receives the output of the accelerator position sensor and determines the opening degree of the throttle valve, and a throttle valve driving device which drives the throttle valve to the position corresponding to the opening degree determined by the throttle valve opening degree determining circuit. The throttle valve opening degree determining circuit is arranged to determine the opening degree of the throttle valve with respect to the amount of operation of the accelerator so that the change in the opening degree of the throttle valve for a given change in the amount of operation of the accelerator is relatively small when the amount of operation of the accelerator is in an intermediate range and is relatively large when the amount of operation of the accelerator is above or below the intermediate range.

Abstract: An automobile engine having a device for increasing the inkage air in idle operation when a load is applied to the engine from equipments associate with the engine. An alternator driven by the engine has a voltage regulator which controls the alternator output in response to a load condition on the alternator by controlling the field current. A control unit is provided to restrict an increase in the field current when an electric load is turned on for a time period required for having the engine output increased.

Abstract: A fuel supply control system for an automobile engine which comprises fuel increasing device operable in response to an output fed from an acceleration detector for increasing the quantity of fuel to be supplied, and a rate-of-increase adjusting device for adjusting the rate of increase of the fuel to be supplied. The rate of increase of the fuel to be supplied becomes high as the air-fuel ratio of the combustible air-fuel mixture detected shortly before the acceleration is high.

Abstract: An air-fuel ratio control system for an automobile engine including an intake passage having a throttle valve, and a fuel supply unit, which comprises an air detector for generating an air signal indicative of the quantity of air sucked to the engine through the intake passage, a throttle detector for generating a throttle signal indicative of the opening of the throttle valve, and a control unit operable in response to the signals from the air and throttle detectors for determining the air-fuel ratio of a combustible air-fuel mixture to be supplied to the engine in dependence on the amount of air sucked when a load on the engine is small, but on the opening of the throttle valve when the load on the engine is great.

Abstract: An engine air-fuel ratio control system in which the engine operating range is divided into a light load, medium load and heavy load regions. In the light load region, a control of the fuel supply is made so as to provide a mixture of leaner than the stoichiometric value. In the medium load region, a feedback control is made based on the signal from an O.sub.2 sensor and, in the heavy load region, a control is made to provide a richer mixture. In the transient between the light load and medium load regions, the air-fuel ratio is changed with a rate which changes in accordance with the rate of change in the engine load.