Engine warm-up phase: the temperature sensor reports the rising coolant temperature to the control unit. It orders the idle speed stabilization valve to close, and the fuel delivery time by the injectors is reduced to normal.
Idle speed: The control unit recognizes from the messages of the throttle potentiometer and the potentiometer on the air flow meter when the engine is idling. If the idle speed drops, the control unit changes the ignition timing; at the same time, the idle speed stabilization valve opens its air channel, thereby increasing the amount of injected fuel.
Normal operation does not require any special devices. The duration of opening of the injection nozzles is determined by the position of the throttle valve and the valve shutter in the air flow meter.
Acceleration: The control unit recognizes rapid opening of the throttle valve from the throttle valve potentiometer as acceleration. Accordingly, the injection duration is increased for a short time.
Lambda regulation: the catalytic converter needs a constant change of rich or lean mixture for perfect operation. The residual oxygen content at a given time lambda probe (located in the catalytic converter) transmits it to the control unit, which in a split second gives the injection nozzles a command for a shorter or longer injection time and, therefore, the amount of fuel.
Fuel cut-off in forced idle mode: information about the foot being removed from the accelerator pedal is again sent via the throttle potentiometer to the control unit. If the coolant temperature sensor simultaneously reports that the engine has reached its operating temperature and the Hall sensor in the distributor reports that the engine speed is over 1500 rpm, the control unit does not issue a command to open the injection nozzles.
Full load: To develop full power with the accelerator pedal fully depressed, the engine requires more fuel. Based on the "full throttle" message from the throttle potentiometer in combination with the fully open valve flap, the control unit recognizes the "full load" condition and increases the injection duration of the injectors, while ignoring the signal from the lambda probe.
Speed limitation: To protect against exceeding the maximum permissible engine shaft speed, the control unit switches off the injection nozzles if the Hall sensor reports a speed of 6400-6500 rpm.
Operation in an emergency: if the signal from one of the information providers does not arrive at all or has a meaningless value, the Digifant injection system does not stop working normally even under these conditions. The control unit selects the so-called reserve value, which is already stored in the memory. Of course, it cannot take into account many operating conditions, but the car still remains on the move. The driver can recognize the absence of a signal from the sensor by insufficient power or poor starting properties.
(This article was previously published on the resource: AUDIMANUAL)