Ignition coils

IGNITION COILS

The ignition circuit is the inductive discharge, static advance type where the high tension is provided from two twin outlet coils fitted at the side of the cylinder head.

The coils used are the closed magnetic circuit type with the windings in a plastic container immersed in epoxide resin. Each coil is connected to the two spark plugs by means of high tension leads with dielectric properties.

In this type of coil the current in the secondary winding (discharge current) always has the same polarity: therefore one end of the circuit has a positive potential and the other a negative potential.

This implies that the discharge current in the secondary winding always flows in the same direction and therefore the sparks for the two cylinders connected to the coil strike in the opposite way:

• in the spark plug with the positive centre electrode the spark strikes from the earth electrode towards the centre one;
• in the spark plug with the negative centre electrode the spark strikes from the centre electrode towards the earth one.

As a result the wear of the electrodes between the two spark plugs in question is different.

Since the intensity of the spark depends on the resistance between the electrodes (dielectric), whilst the spark in the cylinder in the cross-over stage is weak (lost spark), at alsmot atmospheric pressure in the cylinder at the end of the compression stroke, the spark is intense (working spark) by virtue of the high pressure in the chamber.

Wiring connector