Ignition System: Description and Operation

DESCRIPTION AND OPERATION




The Multiport Fuel Injection System consists of sensors which detect the engine conditions, the ENGINE CONTROL MODULE (ECM) which controls the system based on signals from these sensors and actuators which operate under the control of the ECM.
The ECM carries out activities such as fuel injection control, idle air control and ignition timing control. In addition, the ECM is equipped with several diagnostic test modes which simplify troubleshooting when a problem develops.

IGNITION TIMING CONTROL

The ignition power transistor located in the ignition primary circuit turns ON and OFF to control the primary current flow of each ignition coil. This controls the ignition timing to provide the optimum ignition timing with respect to the engine operating conditions. The ignition timing is determined by the ECM from the engine speed, intake air volume, engine coolant temperature and atmospheric pressure. When the engine is cold or operated at high altitudes, the ignition timing is slightly advanced to provide optimum performance.

IGNITION SYSTEM OPERATION NOTES

- This system is provided with two ignition coils (1 and 2) with built-in ignition power transistors (Coil 1 contains power transistor A and coil 2 contains power transistor B). Coil 1 supplies cylinder number 1 and 4. Coil 2 supplies cylinder number 2 and 3.
- Interruption of the primary current flowing in the primary side of ignition coil 1 generates a high voltage in the secondary side of coil 1. The high voltage thus generated is applied to the spark plugs of cylinder number 1 and 4 to generate sparks. At the time that the sparks are generated at both spark plugs, if one cylinder is at the compression stroke, the other cylinder is at the exhaust stroke, so that ignition of the compressed air/fuel mixture occurs only for the cylinder which is on the compression stroke.
- In the same way, when the primary current flowing in ignition coil 2 is interrupted, the high voltage thus generated is applied to the spark plugs of cylinder number 2 and 3.
- The engine control module determines which ignition coil should be controlled by means of the signals from the camshaft position sensor which is incorporated in the camshaft and from the crankshaft position sensor which is incorporated in the crankshaft. It also detects the crankshaft position in order to provide ignition at the most appropriate timing in response to the engine operation conditions.
- When the crankshaft position sensor signal is input into the engine control module, the engine control module turns each ignition power transistor ON-OFF, one by one.
- The cylinder firing order is 1 - 3 - 4 - 2.