Abstract: An engine control apparatus comprises a throttle sensor, a pressure sensor for detecting a pressure in the intake manifold of an engine as a value of the absolute pressure, an engine revolution speed detector, a zone detector for detecting the fact that a signal value indicating a degree of opening of a throttle valve and a signal value indicating an engine revolution speed fall in a predetermined atmospheric pressure detection zone and a processing unit to calculate a value of atmospheric pressure by adding a set value to a signal of pressure upon detecting said values being in the detection zone. A timer may be provided to detect the fact that the signal values of the degree of opening of the throttle valve and the engine revolution speed are continuously in the atmospheric pressure detection zone for a predetermined time.

Abstract: An engine control system in which the sensed intake manifold pressure is initially utilized as the atmospheric pressure, before engine rotation, and is thereafter calculated or updated on the basis of the throttle opening and engine revolution values falling within a detection zone for predetermined time.

Abstract: An engine control apparatus for controlling fuel injection on the basis of a pressure value relating to the intake pipe pressure of an engine. All variations in the engine load are monitored and a detection signal is output when any variation is equal to or larger than a predetermined value. A timer is operable for a predetermined time in response to such detection signals. Fuel injection is controlled in response to the pressure value during the period when the timer is operative and in response to a value obtained by performing low-pass filter processing of the pressure value during the period when the timer is inoperative.

Abstract: A fuel control apparatus for an engine uses an N-bit low-resolution A/D converter to convert the analog output of an air intake pressure sensor. The N-bit output of the converter is multiplied by a prescribed constant to obtain a signal having at least (N+1) bits. The (N+1) bit signal is subjected to low-pass digital filtering and is used by a controller to calculate the pulse width to be applied to a fuel injector. A high resolution can be obtained using an inexpensive N-bit A/D converter.

Abstract: An apparatus for controlling the operation of an engine based on the pressure in an intake manifold. If a change in the pressure in the intake manifold is equal to or less than a predetermined value during a predetermined period within the period from the time when a voltage source is turned on to the time when a starter is turned on, the pressure in the intake manifold is detected and stored. If the engine is not in the start mode, the rate of fuel supply is increased based on an atmospheric pressure detection value. Based on the comparison between the atmospheric pressure value and a predetermined value, a passage for bypassing a throttle valve is opened and closed to control the idling of the engine.

Abstract: The present invention is adapted for providing an idling speed control system of an internal combustion engine, which exhibits a good response for changes in an engine load, comprising: a throttle valve which controls the amount of intake air for the engine; an actuator which includes an electric motor for variably controlling the opening of the throttle valve; a rotation speed detector for detecting the rotation speed of the engine; an idling condition detector for detecting the idling condition of the engine; and a control, responsive to the detected output of the idling condition detector means, for generating feedback control pulses to intermittently drive said electric motor so that the detected rotation speed of the engine under the idling condition may converge into a target idling rotation speed while, responsive to the output of a detector that detects the operation condition of the engine load operated under the idling condition of the engine, or to the detected output of said rotation speed detecto