Ignition System: Description and Operation

- The ignition control system is controlled by the ECM.
The ECM determines the optimal ignition timing according to signals sent from various sensors (which monitor the operating conditions of the engine), and sends a signal to the ignitor.
- The ECM has a "closed-loop" control function with map which provides superb transient characteristics for responsive ignition timing control.
- The ECM receives signals emitted from the pressure sensor, engine coolant temperature sensor, intake air temperature sensor, crankshaft position sensor, etc., to judge the operating condition of the engine. It then selects the optimum ignition timing stored in the memory and immediately transmits a primary current OFF signal to the ignitor to control the ignition timing.
- This system control type features a quick-to-response learning control method by which data stored in the ECM memory is processed in comparison with information emitted from various sensors and switches.
- Thus, the ECM constantly provides the optimum ignition timing in relation to output, fuel consumption, exhaust gas, etc., according to various engine operating conditions, etc.




- Ignition control under starting conditions
Engine speed fluctuates at the starting condition, so the ECM cannot control the ignition timing. When such a condition exists, ignition timing is fixed at 10° BTDC by using the 10° signal.
- Ignition control under normal engine conditions
Between the 97° signal and the 65° signal, the ECM measures the engine speed, and by using this data it decides the dwell set timing and ignition timing according to the engine condition.




- Ignition control under starting conditions
Engine speed fluctuate at the starting condition, so the ECM cannot control the ignition timing. When such a condition exists, ignition timing is fixed at 10° BTDC by using the 10° signal.