System Description

Ignition System:

This vehicle utilizes a distributorless ignition system (DIS) to create high secondary coil voltage to fire the spark plugs. The system is ECU controlled and referred to as Electronic Spark Advance (ESA). By calculating inputs from various sensors, the ECU provides precise ignition timing at any given moment under all operating conditions.

A key system component is the camshaft position sensor, consisting of 3 sensor rotors and pick-up coils. These generate a signal to the ECU in a manner similar to distributor electronic ignition systems. Pulses are generated when rotors interrupt magnetic fields surrounding each pick-up coil.

Together with input from other sensors, camshaft position sensor pulses are used by the ECU to calculate its control of the power transistor. This component (also referred to as an igniter) is an electronic switch which turns current flow to the coils "ON" and "OFF." When the power transistor is energized, it interrupts current flow through coil primary windings. High voltage is then induced from coil secondary windings to fire spark plugs.

The 6 cylinder engine uses three coils assembled as a coil pack unit. Each coil fires 2 plugs simultaneously. At firing, one cylinder is on its compression stroke and the other is nearing the end of its exhaust stroke. Due to circuit design, plugs are grounded to the engine and current flows to both in the same direction. Because there is greater electrical resistance in the cylinder on its compression stroke (containing unburned air/fuel mixture), the system directs more voltage to that plug than to the other being fired at the same time.