An ignition system is a system for igniting a fuel-air mixture. It is best known in the field of internal combustion engines.

 When a high voltage is applied across the electrode of a spark plug it produces a spark across the gap. When such a spark is produced to ignite a homogeneous air fuel mixture in the combustion chamber of an engine it is called the spark ignition system.

 It should provide a good spark between the electrodes of the plugs at the correct timing.  It should function efficiently over the entire range of engine speed  It should be light and effective and reliable in service.  It should be compact and easy to maintain  It should be cheap and convenient to handle

The ignition systems are classified depending upon how the primary energy for operating the circuit is made available as:  Battery ignition system  Magneto ignition system

Most of the models spark ignition engine use battery ignition system. in this system the energy required for producing spark is obtained from 6 or 12V battery, the construction of the battery is depends upon the requirement of the engine. Battery ignition system mainly used in Passenger cars,light trucks,some motor cycles and large stationary engines.

Essential components:  Battery  Ignition switch  Ballast resistor  Ignition coil  Contact breaker  Capacitor  Distributor  Spark plug

The simplest form of spark ignition is that using a magneto. The engine spins a magnet inside a coil, and also operates a contact breaker, interrupting the current and causing the voltage to be increased sufficiently to jump a small gap. The spark plugs are connected directly from the magneto output. Magnetos were used on the small engine's ancestor, the stationary "hit or miss" engine

COMPARISON BETWEEN BATTERY & MAGNETO IGNITIONS SYSTEM Magneto ignition system Battery is necessary, difficult to start the engine when battery is discharged. Maintenance problem is more due to battery. A good spark is available at the spark plug even at low speed. Occupies more space Commonly employed in cars and light commercial vehicles No battery is needed. No maintenance problems. During starting, quality of spark in poor due to low speed. Occupies less space. Mainly used in racing cars and two wheelers. Battery ignition system

In modern automobiles the following two are coming into common use Transistorized coil ignition system (TCI) Capacitive discharge ignition system(CDI)

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