Ignition System: Description and Operation

EZ116K Ignition System










1 - Non-adjustable inductive speed- sensor
The system employs a non-adjustable inductive sensor to detect speed and top dead center (TDC), thereby ensuring extremely accurate timing. The sensor is mounted at the rear of the cylinder block above the flywheel.

The flywheel is provided with 60 markings. Fifty- eight of these consist of drilled holes which deliver speed signals to the control unit, while the remaining two (undrilled) are located 90° before TDC in the first and fourth cylinders respectively. These signals, together with information on other parameters such as load and temperature, are used to determine the instant of firing. As a result, the timing accuracy is of an extremely high order, while adjustment and checking of the function are permanently eliminated.








2 - Active knock control
This means that the timing in each individual cylinder is corrected if knock occurs. Under these conditions, the ignition is retarded successively in the cylinder affected. If this measure is not sufficient, the device transmits a signal to the fuel system control unit which enriches the fuel/air mixture to reduce the combustion temperature and suppress the tendency to knock.





3 - Power stage
Supplied with firing pulses by the control unit, the power stage acts as an electronic switch, maintaining a constant current in the ignition coil, regardless of battery voltage or speed, and ensuring a healthy spark. A standing current switch-off function prevents overheating of the coil if the ignition remains on while the engine is stopped.

4 - Ignition coil
The coil is of a special type with a low-resistance primary winding which enables extremely high voltages to be generated even when the battery voltage is low.

5 - Distributor
The sole function of the distributor is to supply high tension to the spark plugs.





6 - Spark plugs
The ignition leads are well protected inside a compartment in the valve cover.

A plug socket with a rubber retaining insert is used to remove the plugs.





7 - Diagnostic unit
The new ignition system incorporates a self diagnostic function and a functional lest system.

The diagnostic unit, which is common to both the fuel and ignition systems, is dealt with in a separate chapter.