Circuit diagram
Key: "a" electrical connection
| reference | description | electrical diagram correspondence |
|---|---|---|
| (1) | engine management ECU | 1320 |
| (2) | ignition coils | 1131, 1132, 1133 |
| (3) | Spark plugs | - |
| (4) | knock sensor | 1120 |
| (5) | cylinder reference sensor | 1116 |
| (6) | engine speed sensor | 1313 |
Principle of the ignition
The ignition is the operation that consists of causing and maintaining the combustion of the air-petrol mixture sucked in by the pistons into the cylinders of the engine
The air-petrol mixture is ignited by the spark produced by the spark plugs
The air-petrol mixture ignites in concentric layers and so the ignition must be advanced to take account of the duration of combustion
Principle of ignition advance
By causing the ignition before the piston reaches top dead centre (TDC), the force exercised on the piston is at the maximum as soon as it goes past it
The interval in degrees before the instant at which the spark jumps and top dead centre (TDC) measures the ignition advance
The calculation of the ignition advance depends on the following parameters
- Engine speed
- Knock information
- Engine crankshaft position
- Richness of the air-petrol mixture
- Positions of the inlet and exhaust camshaft dephasers
The calculation of the ignition advance is defined by 5 mappings positioned at the operating limits of the inlet and exhaust camshaft dephasers
(1) mapping of the ECU in question 1
(2) mapping of the ECU in question 2
(3) mapping of the ECU in question 3
(4) mapping of the ECU in question 4
(5) mapping of the ECU in question 5
"A" exhaust dephaser angle
"B" inlet dephaser angle
"b" camshaft dephasers positioning point
The engine management ECU knows the ignition advance values of these 5 mappings
E.g.: when the camshaft dephasers are positioned at point "b", the ECU determines the ignition advance value by linear interpolation
Engine management ECU
The power and control stages of the coils are incorporated in the engine management ECU (there is no external ignition module)
The engine management ECU supplies each primary of the coils alternately in the order of ignition (1-3-2)
The ignition is synchronised by the camshaft position sensor
Heating of the catalytic converter
To improve the rise in temperature of the catalytic converter, the engine management ECU adopts a catalytic converter heating strategy
There are 2 catalytic converter heating strategies, functions of the vehicle mileage
For a vehicle with mileage less than 5000 km
- Increase the engine speed to 850 rpm
- Reduce the ignition advance by 2° (crankshaft)
For a vehicle with mileage more than 5000 km
- Increase the engine speed to 1100 rpm
- Reduce the ignition advance by 2° (crankshaft)
The conditions of operation are identical for the 2 strategies, being dependent on the engine coolant temperature
"C" engine coolant temperature when starting (in °C)
"D" engine coolant temperature after starting (in °C)
"E" operating zone of the catalytic converter heating strategy