Ignition Coils

Ignition Coils





The V8 engine is fitted with eight plug-top coils that are driven directly by the ECM (engine control module). This means that the ECM (engine control module), at the point where sufficient charge has built up, switches the primary circuit of each coil and a spark is produced in the spark plug. The positive supply to the coil is fed from a common fuse. Each coil contains a power stage to trigger the primary current. The ECM (engine control module) sends a signal to each of the coils power stage to trigger the power stage switching. Each bank has a feedback signal that is connected to each power stage. If the coil power stage has a failure the feedback signal is not sent, causing the ECM (engine control module) to store a fault code appropriate to the failure.

The ECM (engine control module) calculates the dwell time depending on battery voltage and engine speed to ensure constant secondary energy. This ensures sufficient secondary (spark) energy is always available, without excessive primary current flow thus avoiding overheating or damage to the coils.

The individual cylinder spark timing is calculated from a variety of inputs:
^ Engine speed and load.
^ Engine temperature.
^ Knock control.
^ Auto gearbox shift control.
^ Idle speed control.