The controller performs the following main functions:
- control of the fuel injection system;
- ignition system control and ignition timing control;
- cold engine start control;
- engine idle control;
- regulation of the frequency of rotation of the crankshaft;
- regulation of the oxygen content in the exhaust gases (on vehicles with an exhaust gas converter);
- self-diagnosis.
When starting a cold engine, the controller generates impulses for controlling the ignition timing and impulses for the duration of fuel injection by injectors, the ignition timing is determined based on the crankshaft speed and coolant temperature. The maximum ignition timing is entered at a coolant temperature of -30°C. The duration of fuel injection is determined depending on the intake air temperature, coolant temperature, battery voltage and engine speed. During a cold engine start, each ignition pulse corresponds to an injection duration pulse, i.e. fuel injection occurs four times for each stroke.
The idle speed of the crankshaft is maintained constant by the controller commands.
The values of the ignition timing stored in the memory of the controller are compared with the actual values and corrected accordingly, which makes it possible to exclude changes in the idle mode of the engine as a result of mechanical wear of parts, leaks or differences in friction resistance on different engines.
During acceleration, the controller ensures the enrichment of the combustible mixture as follows. If the signal from the air flow meter potentiometer exceeds the values stored in the controller's memory during acceleration, the controller increases the fuel injection time in such a way as to bring the engine to the required load mode as quickly as possible. As the speed of the crankshaft approaches the required speed, the duration of injection and, consequently, the amount of fuel injected by the injectors gradually decreases.
If the controller receives a signal from the idle contact of the throttle switch, and the engine speed exceeds 1080 rpm, the fuel supply is stopped. At the same time, the engine speed drops, and the intensity of this process depends on the operating conditions of the car. Before entering the idle mode, the controller checks the operation of the system when the fuel supply is cut off.
When the crankshaft speed reaches a certain value, the fuel supply is gradually resumed. In this case, the normal idle mode is set by the controller commands at a lower level than it was when the fuel supply was cut off. This avoids engine interruptions. The controller calculates the moments of stopping and resuming the supply of fuel based on information from the coolant temperature sensor. In addition, the controller has a special program for cutting off fuel supply at low engine load in the memory of the controller. This program starts to run only if the appropriate input parameter is supplied to the controller for some time, provided that the ignition timing is adjusted to the new engine operating conditions.
The self-diagnosis system detects malfunctions of the controller and system components «Motronic ML4.1» and enters them into the memory of the controller.
In the event of a malfunction of the coolant temperature sensors, intake air temperature, air flow meter potentiometer, the controller starts to work according to the default values (default is the program's choice of the value of a variable in the absence of an externally specified value). Once the controller returns to normal mode, the default values are no longer used. To facilitate troubleshooting, it is possible to request current parameters from the controller's memory and activate one or another element of the system by connecting a special device to the diagnostic block.
Visitor comments