Timing for the distributorless ignition system is controlled by an electronic control unit or ECU. The ECU decides the best time to fire the spark plugs.
The ECU makes its decision on the best time to fire the spark plugs based on information received from sensors such as: the MAP sensor, the throttle position sensor, cam angle sensor, crank angle sensor, engine speed sensor and coolant temperature sensor.
Once the ECU has evaluated all the sensor information it makes a decision on when to fire the spark plugs. To do this, the ECU switches the power transistors that control the primary current for each coil pack.
When the primary current is switched the coil produces a high voltage to produce a spark.
The main sensors required to produce correct timing of the spark are the crank sensors. Identification of each pair of cylinders and a signal for their triggering is provided by a dual crank sensor fixed to the engine timing cover. This contains two Hall effect switches sharing a central magnet which forms two air gaps between them.
Two concentric interrupter rings, with a number of blades and windows and mounted on the rear of the crankshaft balancer, rotate through the gaps.
The voltage signals provided allow the ignition module to identify which pair of companion cylinders must be provided with ignition.
