IGNITION SYSTEM
A conventional ignition system should provide sufficiently large voltage across the spark plug electrodes to affect the spark discharge.The ignition system consists of an ignition coil, distributor, distributor cap, rotor, plug wires and spark plugs. Older systems used a points-and-condenser system in the distributor, newer use an ECU, a little brain in a box, to control the spark and make slight changes in ignition timing.
Ignition System is used in SI engine. A given engine design, the optimum spark timing varies with engine speed, inlet manifold pressure and mixture composition.
As air is a poor conductor of electricity an air gap in an electric circuit acts as a high resistance. But when a high voltage is applied across the electrodes 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(SI System).
Ignition system are two types:-
Ignition coil
The ignition coil is the unit that takes your relatively weak battery power and turns it into a spark powerful enough to ignite fuel vapor. Inside a traditional ignition coil are two coils of wire on top of each other. These coils are called windings. One winding is called the primary winding, the other is the secondary. The primary winding gets the juice together to make a spark and the secondary sends it out the door to the distributor.
The Distributor, Distributor Cap, and Rotor
Once the coil generates that very powerful spark, it needs to send it someplace. That someplace takes the spark and sends it out to the spark plugs, and that someplace is the distributor.
The distributor is basically a very precise spinner. As it spins, it distributes the sparks to the individual spark plugs at exactly the right time. It distributes the sparks by taking the powerful spark that came in via the coil wire and sending it through a spinning electrical contact known as the rotor. The rotor spins because it's connected directly to the shaft of the distributor. As the rotor spins, it makes contact with a number of points (4, 6, 8 or 12 depending on how many cylinders your engine has) and sends the spark through that point to the plug wire on the other end.
Spark Plug and Wires
After the coil takes the weaker juice and makes a high powered spark and the distributor takes the powerful spark and spins it to the right outlet, we need a way to take the spark to the Spark plug. This is done through the Spark plug Wires. Each contact point on the distributor cap is connected to a plug wire that takes the spark to the spark plug.
The spark plugs are screwed into the cylinder head, which means that the end of the plug is sitting at the top of the cylinder where the action happens. At just the right time (thanks to the distributor), when the intake valves have let the right amount of fuel vapor and air into the cylinder, the spark plug makes a nice, blue, hot spark that ignites the mixture and creates combustion.
At this point, the ignition system has done its job, a job it can do thousands of times per minute.
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