Ignition System - BOSCH Electronic: Operation

Inputs from engine speed, engine load, detonation, throttle position and battery voltage are supplied to the micoprocessor within the ignition module to determine spark advance. Only the engine load and engine speed input signal values are used to determine the timing signal entered in the memory of the microprocessor. The microprocessor, after analyzing the parameters of engine operation, will adjust timing accordingly.

The ECU output signals provide control for the amplifier module, whose final transistor will make or break the primary coil circuit. The output signals also control the full load enrichening circuit of the injection ECU and the LED knock indicator.

The cartographic ignition ECU with detonation sensor on the Peugeot models, uses a microprocessor associated with a memory where all the criteria to determine spark advance has been programmed. The cartography consists of 16 engine speed reference points and 8 engine load reference points. This gives a total of 128 points of programmed advance settings.

The ECU with knock sensor will reduce the timing advance after analyzing the signal from the knock sensor. Detonation sensing is done cylinder by cylinder. Timing correction is applied to 2 cylinders at a time. If detonation persists, the timing correction will continue until a maximum retard of 22 degrees is reached.