C-class gasoline engines have a high-voltage static ignition distributor, the so-called direct ignition. In such an ignition system, there are no moving parts and a traditional ignition distributor equipped with a runner. As a result, there is no more wear on these parts and the operational reliability is increased.
The actuation of the ignition sparks by means of the ignition coils is carried out directly by the engine control unit, which also controls the petrol injection system. On the 4-cylinder engine, the ignition coils are mounted on the engine block, and on the 6-cylinder engine, under the cover of the high voltage wires of the cylinder head cover. Every two cylinders receive their ignition sparks from one common ignition coil. In this case, one ignites the combustible mixture in the stroke of its intake into the corresponding cylinder. For starting reliability, when starting a cold engine, several igniting sparks are generated per piston stroke (so-called multi-spark ignition).
1. Ignition timing
2. Load
3. Speed
To determine the correct ignition timing, a regulating device is used, based on the ignition characteristic stored electronically. As a result, different operating conditions, such as different fuel grades, can be adjusted relatively easily.
The anti-knock control system for engines starting with a cylinder displacement of 2.2 liters contributes to the operation of vehicles with high compression and smoothes the use of fuels of various qualities. The 4-cylinder engine has one on the engine block, and the 6-cylinder engine has two knock sensors. They regulate the knock combustion in the engine and influence it with the help of appropriate impulses from the engine control device, changing the ignition timing towards the late one. This prevents engine knocking and malfunctions.
If the 1.8/2.0 liter engines predominantly use only low-quality gasoline, the ignition must be switched to a different characteristic using a matching plug in the engine compartment.
When repairing the electronic ignition system, safety regulations must be observed in order to avoid injury to persons involved in these works, or damage to the ignition system.