Ignition Coil: Description and Operation

Ignition Coils:

PURPOSE
Separate ignition coils are used for each spark plug to ensure rapid voltage rise and extremely high ignition voltage.

Electrical Diagram:

OPERATION
The four Direct Ignition System (DIS) coils, use the principle of mutual induction to step up battery voltage (low), to ignition voltage (high). The Ignition Coil contains two sets of copper wire windings around a soft iron core and a threshold release type zener diode. The primary and secondary windings of the coils are uncoupled and the secondary winding has a separate ground. This helps prevent short circuits and suppress high induced voltages back into the primary. The primary winding is made of a hundred or so turns of a heavy gage wire. It is connected to the battery via the ignition switch so that current flows through it creating a magnetic field. When the primary circuit is interrupted by the Digital Motor Electronic (DME) control unit, the magnetic field collapses, and the movement of the magnetic field induces current in the secondary winding of the coil. Since there are many more turns of wire in the secondary winding than there are in the primary winding, the battery voltage is increased to the voltage necessary to ignite the combustion mixture.