Reliable ignition operation throughout the entire engine operating range is an essential factor for the efficient operation of the catalytic converter.
Ignition of a small cloud of finely dispersed fuel-air mixture by a spark is sufficient to initiate the entire ignition process.
The spark plug determines the length of the spark, which also depends on the type and design of the ignition system, as well as the conditions under which ignition occurs.
For a spark to occur, the voltage between the spark plug electrodes must increase sharply from zero to the voltage required to form an arc. After the spark discharge occurs, the voltage drops to the level required for the spark to propagate, causing the fuel-air mixture to ignite.
To obtain spark energy, an ignition coil is used, which operates on the principle of an autotransformer and accumulates ignition energy. When current is supplied to the primary winding of the ignition coil, the energy of the current is converted into the energy of the magnetic field until the moment the current supply is stopped, the magnetic field is sharply reduced, inducing in the secondary winding of the ignition coil.
Cars with 4-cylinder engine
The ignition system is integrated with the fuel injection system, and together they form an engine management system with a common electronic module.
The ignition system consists of a control unit (ignition coil unit) and the knock sensor.
The contactless ignition system does not have a mechanical ignition distributor. With each control current pulse supplied by the control unit, the ignition coil supplies a pulse to two spark plugs at once. One spark discharge ignites the fuel mixture at the end of the compression stroke, and the second occurs on the exhaust stroke, where the ignition spark has no effect on engine operation and is therefore wasted. After further rotation of the crankshaft, the ignition coil again sends an ignition pulse to both spark plugs at once, but this time, where previously the spark discharge occurred in the cylinder on the exhaust stroke, the end of the compression stroke occurs and the fuel mixture ignites, and vice versa.
A dual spark ignition coil is essentially two separate coils, each delivering the ignition pulse to one cylinder.
The electronic control unit uses signals from various sensors to calculate the required ignition timing and charging time for the ignition coils.
The knock sensor is installed on the cylinder block and notifies the electronic control unit of approaching detonation.
The sensor is sensitive to vibration and detects detonation that occurs at the moment of early ignition.
The knock sensor sends a signal to the engine control unit, which in turn reduces the ignition timing until detonation stops.
Cars with V6 engine
These engines have two knock sensors (one for each cylinder block), and the ignition control unit has six outputs and consists of three separate coils, each serving two cylinders.
Precautions when working with the ignition system:
- The legislation classifies ignition systems as systems that are an increased source of danger. Therefore, when working on ignition systems, you must comply with special safety regulations. Persons with a pacemaker are prohibited from working on the ignition system. To avoid exposing yourself to unnecessary danger, entrust work on ignition system components to a service center. You must also exercise extreme caution when performing maintenance work.
- Never touch live elements of the primary and secondary circuits of the ignition system when the ignition is on - this is life-threatening.
- Before carrying out any work on the ignition system, first turn off the ignition. This rule must also be observed when disconnecting and connecting electrical wires or connecting measuring instruments.
- With the ignition on, the rocking of the car is enough to cause a high voltage pulse. Therefore, when carrying out work in the engine compartment, you put your life at risk, and in addition, the main components of the ignition system may be damaged.
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