Air-fuel mixture control for automobile engine having fuel injection system

摘要

An air-fuel ratio control system for an automobile engine of a type having a fuel injection system wherein at least two of parameters including the engine speed, the opening of a throttle valve and the negative pressure developed inside a fuel intake passage are utilized to detect the rate of flow of incoming air to be mixed with an injected mist of fuel to form a combustible mixture. The fuel injection system includes a fuel adjusting device so designed as to provide, when the engine operates within a particular operating region, the combustible mixture of an air-fuel mixing ratio lower than that to be supplied to the engine when the latter operates within the other operating region than the particular operating region. The control system comprises a first EGR control device for controlling an EGR control valve according to a control value stored in a memory when the engine operates within the particular operating region and a second EGR control device operable when the engine operates within the other operating region for controlling the EGR control valve in dependence on the concentration of a component of exhaust gases sensed by a composition sensor.