Ignition System: Description and Operation

MPI Engine Management System:

The MPI engine management system is a fully electronic fuel injection and ignition control system. The system is similar to the Bosch LH-jetronic system and combines fuel injection and ignition control functions into a single electronic control unit (ECU). The ECU monitors various engine sensors and uses this information, compared with information stored in its memory, to precisely control the fuel and ignition systems for lower exhaust emissions, better fuel economy and better engine performance, under all operating conditions.
Ignition control is managed by the computer, through signals to a power switching transistor (power output stage) that operates the ignition coil. The signal timing (ignition timing) and duration (dwell) is determined by inputs from the coolant temperature sensor, hall sensor, air mass sensor, crankshaft position (reference) sensor, engine speed sensor, and knock sensors mounted on the engine.
Only the output devices and secondary ignition components are covered in this section. For complete information on computer control of the ignition system and the sensors and signals that influence it, refer to COMPUTERIZED ENGINE CONTROLS.