Ignition Systems

Ignition Basics

Once you understand the basic principle of an internal combustion engine, it is easy to see why an ignition system plays a crucial role.

For those readers who might need a brief  refresher on what happens inside their engine's cylinders, all modern engine run in a four cylinder of four stroke mode. Let's start with the intake stroke. Here the piston is traveling down in the cylinder, creating a suction that draws the air fuel mixture in through the open intake valve. When the piston reaches the bottom of its stroke, it starts back up again, starting the compression stroke, in which the valves close and the piston compresses the air fuel mixture. This makes the air fuel mixture very dense and capable of releasing a lot of energy when the mixture is ignited. Just before the piston reaches the top of its stroke, the spark plug ignites the mixture, beginning the power stroke, in which the rapidly-expanding gases from the burning mixture raise the cylinder pressure dramatically and this pushes the piston down the bore. The force on the crankshaft each time a power stroke pushes down is what makes the engine go. By the time The piston reaches the bottom of this stroke, the energy in the cylinder has gone and the piston starts back up again, on the exhaust stroke. The cylinder contains the mostly-inert residual gases left from combustion, and when the exhaust valve opens during this stroke, these gases are pushed out of the cylinder and past the exhaust valve as the piston rises.