Circuit diagram
Key
- "A" electrical links
- "B" fuel in the tank
- "C" fuel system
| reference | description | electrical diagram correspondence |
|---|---|---|
| (1) | engine fusebox | PSF1 |
| (2) | Built-in Systems Interface | BSI1 |
| (3) | engine management ECU | 1320 |
| (4) | petrol injector (1), (2), (3), (4) | (1331, 1332, 1333, 1334) |
| (5) | pump, gauge and fuel pressure regulator assembly | 1211 |
| (6) | petrol injector supply rail | - |
| (a) | valve SCHRAEDER | - |
Control of the injection
The engine ECU receives and converts the demands from the driver, or from the vehicle (ABS, ESP, automatic gearbox), into information on the necessary torque that is required of the engine
The engine ECU determines the quantity of fuel that is necessary to provide the engine torque that is required
As a function of the fuel quantity calculated, the engine ECU determines the fuel injection time
To comply with the emission standards, limit the combustion noises and improve the driving performance, the engine ECU determines the time for each injection of fuel during an engine cycle
Management of injection on starting
Injection on starting
As the engine is started, there is injection by all four injectors (simultaneous injection), then changing to sequential mode
Simultaneous injection helps the engine in starting from cold
This simultaneous injection phase occurs only once - on starting, the injector operating time in this phase being a function of the coolant temperature
Anti-flooding strategy
If the engine does not start, the engine ECU switches to the anti-flooding strategy
The anti-flooding strategy prevents the engine from becoming flooded by repeated attempts at starting
On starting, during the first 12 seconds, the ECU applies a normal strategy then reduces the injection time to 0
In order to return to a conventional starting strategy, you have to switch off the ignition and then restart the engine
Pressure of fuel in the injection rail
Specificities
The fuel supply pump provides a pressure of 3,5 bars (The pressure is regulated by a pressure regulator inside the supply pump)
When you switch on the ignition, the fuel supply pump is operated for 3 s, then, on starting, the pump is supplied permanently
Valve SCHRAEDER
The SCHRAEDER valve is like a tyre valve
Functions of the SCHRAEDER valve
- Depressurising the circuit
- Pressure check
- Delivery check
Starter motor circuit
For the engine to start, it is necessary to have a minimum pressure in the injection rail
This pressure is variable depending on the air temperature; the lower the air temperature, the greater the pressure in the injection rail
| air temperature | pressure of fuel in the injection rail |
|---|---|
| from - 20°C and below | 3,5 bars |
| from - 5°C to - 20°C | 3 bars |
| from 50°C to -5°C | 2,7 bars |
Fuel injection time
General
Fuel injection pressure being equal, a longer (or shorter) injection time allows more (or less) fuel to be injected
The fuel injection time corresponds to the time during which the engine ECU commands the fuel injectors to be open
The opening control time for the fuel injectors corresponds to a given mass of fuel injected
The mass of fuel injected depends on the mass of air admitted into the engine
The engine ECU uses a ratio between the mass of fuel injected and the mass of air admitted into the engine; this ratio is called the stoicheometric ratio (richness 1) corresponding to 1 g of fuel injected for 14,7 g of air admitted
Advantages of this setting: richness 1
- Attainment of a combustion that is perfect
- Attainment of a maximum performance by the engine
- Reduction in the emissions of polluting gases
Specificities
The fuel injection time is calculated as a function of the following parameters
- Engine speed
- Engine load
- Vehicle speed
- Coolant temperature
- Inlet air temperature
- Intake air pressure
- Richness 1
- Protection of components (exhaust manifold - catalytic converter)
The injection time is very little impacted by the information coming from the oxygen sensors because the engine ECU has that richness setting 1
When there is full load, the engine ECU operates on a richness higher than 1 and ignores the information from the oxygen sensors in order to protect the components
Fuel supply cut-off
When a pyrotechnic component is triggered, the supply of the fuel pump is cut off by the engine fusebox (PSF1) via the information about the triggering coming from the airbag ECU
To restart the engine after a fuel supply cut-off, it is necessary to connect the diagnostic tool