The ignition system is the system, which consists of devices that serve to create an electric spark of high voltage. The ignition system is generating a very high voltage (from 20 to 30 thousand volts) from the car’s 12Volt battery. This voltage is necessary to igniting the fuel-air mixture in the engine ‘s combustion chambers. The spark plugs are supplying a high voltage spark to the combustion chambers in determine time.
The main types of ignition systems:
- Contact point ignition system;
- Contactless ignition system;
- Microprocessor ignition system.
All types of ignition systems are designed for one thing – the creation of a high voltage tension, and differ only in the ways of creating a control pulse.
High voltage producing
The component that produces the high voltage is ignition coil. Ignition coil operation is to convert the low voltage current (from the battery) to high voltage current (when the distributor contacts open).
Ignition system components
The ignition distributor is used to distribute high-voltage electric ignition to the engine cylinders. The ignition distributor consists of bowl, contact-breaker, central shaft and distributor cam.
The contact-breaker points are located into the bowl. There are rotor arm and device for altering the ignition timing inside the bowl too. Distributor cap closes the bowl.
The central electrode is on the distributor cap, which is made of nonconductive plastic. The coil feds the high voltage current to the central electrode. There are segments inside the cap. These electrodes or segments are connect to sparkplug leads.
Forced ignition does not exist in diesel engines, there is spontaneous combustion.
The rotor arm and central electrode connected by a spring in the distributor cap. When the rotor arm revolves, the current enters to the each spark plug through the central electrode and the brush. As the rotor arm comes a segment, the contact-breaker points open. High voltage current passes to the relevant sparkplug lead through the rotor arm. The contact-breaker points act as a switch that cuts off and reconnects again the low-tension circuit to the coil (high-tension circuit).
Cams on the central shaft open the points (four-cylinder engine have four cams, so each full rotation of the shaft the points open four times), and then a spring arm closes them. As the points open, the magnetic field in the primary winding is fall down so the high voltage current is induced. Finally, the current is transferred to the sparkplugs through the distributor cap.
A spark is supplied to spark plugs at certain times.
If you need you can alter timing of the spark, you should adjust relation the position of the points and the distributor’s body in relation to the central shaft.
In modern cars, ignition systems have special microelectronics that ensure the optimum ignition timing adjusting, regardless engine speeds and engine load.
Ignition system circuit
The sparkplugs are mounted into the combustion chambers in the cylinder head of the engine.
High voltage current passing
Segment on the distributor cap – plug leads – plug caps – central electrode – nose of the plug.
The gap between side electrode and the central one usually is from 0.6 mm to 0.9 mm.