Diagram showing operation of ignition

The ignition coil is made up two primary windings, connected to the control unit (A) by terminals 1 and 19, supplied by the battery voltage and two high tension secondary windings whose outlets are connected directly to the spark plugs for cylinders 1-4 and 3-2.

The high tension reaches the pair of spark plugs each time the circulation of the current in the primary winding is interrupted by the power module. The static distribution of the high tension takes advantage of the different pressure conditions which exist at the same time in the pairs of cylinders 1-4 and 3-2. If in these conditions the voltages necessary to strike the spark between the spark plug electrodes are examined, it will be seen that during the compression stroke the voltage is very high (10-15 kV), whilst during the cross over the voltage is greatly reduced (in the order of 500 V).

The secondary circuit for each coil is therefore closed by two sparks; one with around 500 V also known as the lost spark because it occurs in the cylinder during the exhaust stroke, the other between 10-15 and more kV in the cylinder in the compression/explosion stroke suitable for burning the mixture in the actual cylinder.

Diagram showing operation of ignition

1. Rpm and TDC sensor
2. Flywheel
3. Signal from flywheel (60 - 2 teeth)
4. Order of rectangular wave signals
5. Ignition power module (internal)
6. Ignition
7. Spark plugs

NOTE The numbers indicate the corresponding terminals of the control unit.