Ignition System: Description and Operation

IC (IGNITION CONTROL) SYSTEM
This system controls electronically the time of electric current flow to ignition primary coils as well as ignition timing.
ECM (PCM) judges the engine condition by using signals from various sensors, selects the most suitable electric current flow time and ignition timing for that engine condition from among those prestored in its memory and sends an ignition signal to the igniter in the ignition coil assembly.
The igniter in the ignition coil assembly turns ON and OFF the primary current of the ignition coil according to the signal from ECM.
Control of the system includes three different types as follows.
- Ignition timing control at engine start
- Ignition timing control after engine start
- Electric current flow time control


GENERAL DESCRIPTION
The ignition system used for this vehicle uses a direct ignition system so as to avoid jamming caused by the secondary voltage which occurred in the ignition coil and ensure stable ignition even during a high engine speed. Also, IC (Ignition Control) system is adopted to obtain the ignition timing suitable for the every engine conditions.
The components of this system are as follows.
- ECM/PCM
It detects the engine condition through the signals from the sensors, determines the most suitable ignition timing and time for electricity to flow to the primary coil and sends a signal to the igniter in the ignition coil assembly.
- Ignition coil assembly (including an ignitor)
The ignition coil assembly has a built-in ignitor which turns ON and OFF the current flow to the primary coil according to the signal from ECM (PCM). When the current flow to the primary coil is turned OFF, a high voltage is induced in the secondary coil.
One ignition coil assembly is in charge of ignition of one cylinder only.
- Camshaft position (CMP) sensor
Being photoelectrically operated, this system converts timing and time by and during which the light is received at the light receiving part in the CMP sensor into the electric signals. It also outputs the engine speed (position) signal and the cylinder identification (reference) signal to ECM/PCM.
- Spark plug
- TP sensor, ECT sensor and MAF sensor
The direct ignition system does not have a distributor or high tension cords but each cylinder has an ignition coil assembly (igniter and ignition coil) and the secondary voltage which occurred in the ignition coil is sent to the spark plug directly.
In IC (Ignition Control) system, the ECM/PCM is programmed for the best ignition timing under every engine condition. Receiving signals which indicate the engine condition from the sensors, e.g., engine revolution, intake air volume, coolant temperature, etc., it selects the most suitable ignition timing from its memory and operates the igniter in the ignition coil assembly. Thus ignition timing is controlled to yield the best engine performance.