Audi Car ignition system electrical circuit diagram
Audi Kettering or CB points ignition system
Kettering ignition system or CB points ignition system was the very common and popular ignition system for the last 100 years. This system was developed or invented by scientist Charles Franklin Kettering in 1906. The Kettering ignition system uses a battery, CB points, capacitor, and distributor for ignition. Before the Kettering system vehicles were using magneto ignition system. In a magneto ignition system, there is no battery and the voltage for the ignition system is produced by a small permanent magnet generator known as a magneto. Magneto ignition system is still used on small engines and motorcycles. Both magneto ignition and Kettering ignition system have their own benefits and limitations. All petrol engines need a spark to combust the air-fuel mixture. For combustion, a spark plug is installed in the engine cylinder head. When the piston reaches the top dead center during combustion stroke, a spark is supplied by the ignition system to combust the air-fuel mixture and an explosion takes place inside the engine cylinder which produces the mechanical power or torque.
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| Kettering ignition system point ignition circuit |
Kettering ignition system working principle
- Refer to the circuit diagram, when the ignition switch is moved to a close position, electrical energy flows to the primary winding of the ignition coil through the fuse.
- When the contact breaker points close, the coil gets ground and current flows through the primary of the ignition coil. this flow of current creates a magnetic field around the primary coil.
- Next, when the points open, the magnetic field collapses, and the energy of the magnetic circuit releases in the secondary coil of the ignition coil. This energy is in the form of high voltage and low current. This is due to the very high number of secondary coil turns of fine wire.
- Those high voltages are enough to spark on the spark plug.
- The spark produced is directed to the corresponding cylinder by the distributor. As it is a must to perform the ignition at right time, the distributor performs this job.
- There is a need for spark advance. The reason for spark advance is needed at high engine rpm. At high engine rpm, the piston moves very fast inside the cylinder. This combustion of air-fuel mixture needs little time to take place. If the spark is applied at the top dead center at high rpm, there will be a delay due to air-fuel mixture combustion. This will degrade the engine performance at high rpm. To meed such a problem, a vacuum spark advancer is used which automatically advances the ignition timing at high engine rpm.
Audi Kettering ignition system and magneto ignition system advantages and disadvantages:
| Magneto Ignition System | |||
Advantages | Disadvantages | Advantages | Disadvantages |
| Magneto systems don't need a battery to operate. This system generates its own energy. It is suitable for most small engines. | The Kettering ignition system needs a battery to operate. Due to battery this system becomes expensive and needs to look after | ||
| As magneto is producing its own power. The generation is weak at startup due to less engine speed. This type of ignition has poor starting characteristics. | Due to the high power available from the battery during startup, the starting is better and smooth | ||
| In a magneto ignition system, few numbers of components are used which makes the system more reliable and low cost. | In Kettering ignition much more components are used which makes the system more complex and complicated. Due to the complexity of the circuit more problems and defects could come in systems and the cost of the system increases. | ||
| As the engine speed increases, the generated voltage by magneto also increases due to to which the system performance increases. | Kettering ignition system performance decreases with the high engine speed. | ||
| It needs multiple coil packs to fire in multiple cylinders for the Kettering ignition system | A single-coil pack with a distributor is enough to spark in multiple cylinders | ||
| Magneto systems are normally simple and reliable in construction. They need a permanent magnet, an ignition coil, a point or equivalent electronic switching arrangement to perform the job with simplicity and low cost. | Kettering ignition system is obsolete now and is replaced with the modern computer or ECU controlled ignition system which needs multiple coils to fire in multiple cylinders. | ||
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