Digital Ignition Timing Control: Operation

As the crankshaft rotates, the crankshaft sensor sends pulses to the computer control unit. From these pulses, the computer control unit determines engine speed and crankshaft (piston position) position. When the engine is running, the computer control unit receives information from the various engine sensors and determines the appropriate time to signal the ignition control unit. The ignition control unit makes and breaks the circuit to the coil, thus firing the spark plug. The computer control unit also controls idle speed, whenever accessories (A/C, lights, etc.) are turned on, by advancing or retarding the ignition timing. With this system, idle speed is adjusted using a timing light.

Fig 1: Porsche Digital Ignition Timing Control Showing Component Location

Courtesy of PORSCHE CARS NORTH AMERICA, INC.

Fig 2: Porsche Digital Ignition Timing Control Wiring Diagram

Courtesy of PORSCHE CARS NORTH AMERICA, INC.