Ignition control is carried out by means of a common electronic ignition and injection control unit. This occurs alternately through the two ignition coil units.
The ignition timing is changed in accordance with the characteristics stored in the control unit memory and depends on the engine speed and load. Engines produced since mid-1995 use a characteristic ignition system with an inductive sensor, designated "EFZ-i". The control unit determines the position of the crankshaft using a signal from the flywheel sensor. Other factors that determine ignition timing include throttle position, coolant temperature, and intake air absolute pressure.
The flywheel has a special toothed rotor, the teeth of which are unevenly distributed. The two teeth are at a distance of 180° so that one of them determines the TDC, the other the BDC of the sensor. Information about this is transmitted to the control unit.
The ignition coil on older engine models or the ignition module on newer ones may be disconnected as described in the previous section. The same applies to the ignition distributor of other engines.
The ignition system installed on most engines consists of the following parts:
1. The sensor is installed in the flywheel housing.
The sensor provides the ignition module with information about the flywheel position at which a spark should be generated.
2. An electronic control unit that is also used to control the injection system.
3. Ignition module.
4. Ignition coils or ignition distributors.
5. Ignition distributor.
6. The 16V engine has a position sensor mounted on the cylinder head. It is tuned to a specific camshaft of the intake valves and recognizes the TDC of the first cylinder (once per working stroke, i.e. every two revolutions).
The ignition system determines the ignition timing in each cylinder in accordance with the data stored in the electronic memory. The memory receives data from individual sensors, namely from the flywheel sensor (engine speed and flywheel position), measuring the volume or mass of the intake air (engine load), air temperature (the sensor is located in the air volume or mass meter) and coolant temperature. The throttle potentiometer provides information on the throttle position during starting, idling, under load and in forced idle mode. The ignition spark signal is supplied from the injection/ignition control unit to the ignition module, which controls the ignition. When carrying out any work on the cables or connections of the ignition system and the associated injection system, the ignition must always be switched off. For safety, the battery must also be disconnected if any cable is disconnected. This eliminates the possibility of a short circuit.
For information on ignition timing, checking it, etc., see. Checking the ignition timing.
It is necessary to say a few words about the detonation control and the detonation sensor present in the M1.5.4 injection system.
Combustion accompanied by detonation knocks in the engine and resulting from early ignition is dangerous for the engine if it is running for a long time. It causes serious damage to the crankshaft bearings and pistons.
However, in modern cars the maximum possible, earliest ignition is installed. In order to correctly set the ignition timing during engine operation, without causing detonation, various factors are taken into account. For this purpose, detonation control is used.
The combustion process in the cylinders is controlled by a so-called knock sensor, i.e. an electrical sensor that detects sharp knocks - "detonation" - appearing in the cylinder. The sensor is screwed into the cylinder block. When uneven knocks appear in the cylinders, information about them is transmitted to the control unit, which processes it as follows:
1. As soon as the control unit receives a signal about the appearance of detonation knocks during combustion, it determines in which cylinder the knocks appear. The ignition timing of the identified cylinder shifts by 3 towards later ignition, while in the remaining cylinders the ignition timing does not change.
2. If the engine continues to run with knocks, the control unit again shifts the ignition timing back by 3. This can be repeated several times.
3. If knock-free operation of the cylinder is achieved in this way, the ignition timing is moved to an earlier position after some time. But this time by 0.5. Then, during the engine operation, for each stroke, the ignition timing shifts by 0.5 towards earlier ignition until the previous ignition timing is reached again. In between, knocking sounds may appear in other cylinders.
The diagram shown is a general detonation control diagram. For Opel engines, the above adjustment angles have their own values.
Visitor comments