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Ignition system

Ignition system


General

The role of the ignition system is to provide the igniting spark. The ignition system consists of six inductive ignition coils - one for each cylinder - with integrated power amplifier.

The ignition coils are mounted on top of the spark plug of the respective cylinder and are secured with a screw. The coils can be replaced individually.

Function


General

The ignition system consists of six inductive ignition coils - one for each cylinder. The ignition coils are supplied B+ from the main relay (229) on pin 2 while pin 4 is connected to grounding point G7F for the front bank or G7R for the rear bank.

When the main relay is pulled, B+ is supplied to pin 2 of the ignition coils. When ECM supplies pin 1 of the respective ignition coil a pulse of 20 mA, a power transistor integrated in the ignition coil closes the primary circuit. The primary winding consists of relatively few coppar wire coils. A magnetic field gradually builds in the ignition coil. When the spare is to be fired, ECM stops supply B+ to pin 1 and induces (builds up) a high voltage across the ignition coil's secondary winding.

The time during which ECM supplies pin 1 with the pulse and the magnetic field is formed in the ignition coil depends on battery voltage and engine speed. See "charging times, ignition coils" for more information. The voltage on the secondary side is very high as there is a large number of copper windings. This voltage builds up until a spark crosses the spark plug gap. This takes place at approx. 5-30 kV depending on the prevailing conditions in the cylinder in question. The high pressure that arises from high loading of the engine requires a higher voltage compared to lighter operating conditions.

The ignition coils can generate voltages of up to 40 kV.

Four ignition trigger lines from ECM are connected to the ignition system as follows:


• Ignition coil 320a for cylinder 1 is connected to ECM pin 42(A)

• Ignition coil 320b for cylinder 2 is connected to ECM pin 26(A)

• Ignition coil 320c for cylinder 3 is connected to ECM pin 58(A)

• Ignition coil 320d for cylinder 4 is connected to ECM pin 9(A)

• Ignition coil 320e for cylinder 5 is connected to ECM pin 41(A)

• Ignition coil 320f for cylinder 6 is connected to ECM pin 25(A)


Charging time, ignition coils


Ignition coil changing time depends on system voltage and engine speed. To obtain the right energy/voltage in the spark, not more that would cause ignition coil wear or less that would cause misfires, charging time is compensated for battery voltage and engine speed.

The charging time is around 3 ms at normal system voltage.

A relatively low battery voltage requires a longer charging time to obtain the same spark energy/voltage.

Conversely, a relatively high battery voltage gives a shorter charging time in order to prevent unnecessary heating of the ignition coils and to reduce wear on the spark plug electrodes.