Ignition System: Description and Operation

Engine Management System:

Ignition pulses are supplied to a separate ignition power module, then to the ignition coil which generates a high voltage pulse. This high voltage pulse is routed from the ignition coil through the distributor to the spark plugs where it ignites the air/fuel mixture.

The distributor has no centrifugal or vacuum advance mechanisms and no primary circuit, the distributor is only required to distribute the high voltage spark to the spark plugs.

Ignition timing is controlled by the ECM, using the information supplied by the air mass meter and crankshaft sensor as inputs. This information is used to access mapped data stored in 128 memory locations containing ignition timing angles pertaining to eight engine loads at 16 different speeds.

Depending on the input sensors and supply voltage, the dwell-period (dwell angle) is determined and the ignition energy is adapted to that required by the engines demand. The unnecessary consumption of energy in the ignition coil is thereby prevented. In addition, a peak coil current cut-off facility is used to prevents current flowing through the ignition coil below a specific engine RPM and, therefore, preventing battery drainage and ignition coil damage.