The ignition system consists of the following main elements:
- ignition coils
- spark plug
- ignition distributor with Hall sensor and runner
- ignition control unit (TSZ, VEZ, Digifant, Motronic)
Carburetor engines, like engines with the Mono-Jetronic injection system, are equipped with a transistorized ignition system (TSZ).
The 16-valve engine without a catalyst, designated KR, is equipped with a transistorized ignition system with an additional control unit. This system is called the electronic ignition system (VEZ).
In engines with the Digifant ignition and injection system developed by VW, the VEZ system is integrated into the injection system control unit and is supplemented by a knock control.
The BOSCH Motronic system, installed on 16-valve and 6-cylinder engines, has only one ignition and injection control unit.
TSZ-H system
Transistor ignition system (TSZ) is contactless. Instead of an interrupter, the ignition distributor is equipped with a maintenance-free Hall sensor (TSZ-H). A capacitor is not needed here. The Hall sensor consists of a non-contact magnetic guard and a rotary diaphragm fixed on the distributor shaft.
VEZ system
Electronic ignition system (VEZ) is a transistor system with an electronic control unit. The task of the ignition control unit is to regulate the ignition timing, based on the characteristic fields once stored in the memory device (management cards). In the TSZ system, ignition timing is controlled by a vacuum-controlled centrifugal governor.
Digifant ignition and injection system
In this system, electronic ignition and injection control are combined in one unit. This is a transistorized ignition system with a Hall sensor and an electronic ignition timing control unit. The ignition timing is controlled on the basis of the fields of ignition characteristics once stored in the memory. By design, the Digifant system basically corresponds to the VEZ ignition system. However, the ignition timing is additionally influenced by the signal from the knock sensor.
KE ignition and injection system - Motronic
The ignition distributor with a Hall sensor is similar in design to that used in the VEZ system. The ignition timing is also controlled on the basis of the ignition characteristic fields once stored in the memory. The ignition coil voltage output stage, comparable to the TSZ-H switch of other ignition systems, is located next to the ignition coil and is designed to control the current of the ignition coil based on signals from the control unit. Thanks to two knock sensors, the occurrence of knocking in each individual cylinder is detected and the ignition timing for that cylinder is automatically adjusted. Additionally, an inductive sensor is installed on the high voltage wire for cylinder 4, which, at the moment a spark occurs, supplies the control unit with a voltage signal that is necessary to use the signals from the knock sensors.
Motronic M2.7 / M2.9 system in a 6-cylinder engine
While the M2.7 system still has an ignition distributor, in vehicles with a chassis number from 31 ZNE 139 739 (around 9/92), a non-contact ignition system is used. The distribution of high voltage to the individual cylinders is carried out here by means of electronically controlled parts operating in a static mode, which have replaced the traditional mechanical distributor with a runner. The system has 3 ignition coils located in the same housing, which are mounted on the engine cylinder head. The synchronization of the ignition system is carried out using the signals that the Hall sensor sends to the control unit. The sensor is located on the side of the cylinder head and measures the camshaft speed.
Digifant and Motronic systems: self-diagnosis
The Digifant system of engines with a displacement of 2.0 liters from 8/92, like all Motronic systems, has the ability to self-diagnose. This means that faults that occur in the injection and ignition systems are stored in the memory of the control unit in the form of codes. These codes can be read in the VAG workshop, after which the identified malfunctions are purposefully eliminated.
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