Due to the high voltage, the spark plug creates a spark that ignites the compressed air-fuel mixture in the combustion chamber. The electronic control unit of the engine turns on and off the current of the primary circuit of the ignition coil, thus regulating the ignition timing.
Via the crank angle sensor in the ignition distributor, the engine control unit determines the position of the crank angle and generates the optimum ignition timing for the given engine condition.
If the engine is cold or the vehicle is driven at high altitudes, the ignition timing is slightly advanced in order to optimally adapt the power to the given operating conditions.
If the engine knocks, the ignition timing is slowly retarded until knocking stops.
When the car is equipped with an automatic transmission, the ignition timing occurs with a delay in order to soften the moment of switching on the drive and thereby reduce the shock when the gear is engaged.
The ignition system of the 4G1 engine is shown in fig. 7.29.
Pic. 7.29. 4G1 engine ignition system
Table 7.1a. Technical data of the 4G1 engine ignition distributor
Type | Contactless distributor with built-in ignition coil |
Setting | Electronic |
Ignition order | 1-3-4-2 |
Table 7.1b. Technical data of ignition coils
Engine | 4G1 | 4G9 |
Ignition type | Enclosed single coil with integrated distributor | Closed binary ignition coil |
Table 7.1c. Ignition coil
Engine | 4G1 | 4G9 except MW | 4G9MW |
Primary coil resistance | 0.5-0.7 ohm | — | — |
Secondary coil resistance | 15-22 ohm | 14-21 ohm | 20-30 ohm |