Schematic diagram
Key
- "A" fresh air
- "B" hot compressed air
- "C" cooled compressed air
- "D" control vacuum
- "E" electrical links
| reference | designation | electrical diagram correspondence |
|---|---|---|
| "a" | turbocharger regulator valve control vacuum capsule (with position copy sensor) | 1374 |
| (1) | air metering unit (with position copy sensor) | 1389 |
| (2) | engine ECU | 1320 |
| (3) | variable geometry turbocharger | - |
| (4) | proportional electrovalve controlling the variable geometry actuator of the turbocharger | 1229 |
| (5) | turbocharger air cooler | - |
| (6) | air filter unit | - |
| (7) | inlet air pressure and temperature sensor | 1312 |
| (8) | air flowmeter by mass | 1310 |
Management of the air supply
The engine ECU adapts the mass of air entering the engine to the needs relating to the different life phases
In order to adapt the mass of air entering the engine, the engine ECU acts on the following components
- Pneumatic control of the variable geometry actuator of the turbocharger to vary the turbo air pressure (via a solenoid valve)
- EGR (exhaust gas recycling) electrovalve
- Air metering unit
The flowmeter for the air mass measures the flow and the temperature of the air entering the turbocharger and transmits the information to the engine ECU
The inlet air pressure and the temperature on exit from the air metering unit are measured and transmitted to the engine ECU by the inlet air pressure and temperature sensor
The atmospheric pressure sensor is incorporated in the engine ECU
Turbo air pressure
General
At an equal temperature, the mass of air entering the cylinder increases with the turbo air pressure
The turbo air pressure delivered by the turbocharger increases with the engine speed
The engine ECU has to adapt the turbo air pressure to the user's requirements
Specificities
The engine ECU operates the turbocharger variable geometry control actuator in relation to a pre-defined turbocharging air pressure reference value
The turbo air pressure reference is calculated from the following parameters
- Engine speed
- Engine load
- Engine coolant temperature
- Inlet air temperature
- Atmospheric pressure
The engine ECU converts the setting for the turbo air pressure into a setting for the position of the variable geometry actuator of the turbocharger
The engine ECU is able to manage the turbocharging pressure in accordance with 2 operating modes
- Piloted mode
- Regulated mode
Piloted mode (open loop): the engine ECU operates the turbocharger variable geometry control actuator in order to control the turbocharging pressure, in accordance with the turbocharger wastegate valve position reference value
Regulated mode (closed loop): the engine ECU operates the turbocharger variable geometry control actuator to regulate the turbocharging pressure, in accordance with an absolute air pressure reference value
The following strategies are used in the event of a turbocharging pressure sensor fault
- Change to piloted mode
- Lighting of the injection system fault warning lamp
- Deactivation of the vehicle cruise control and speed limiter (according to model)
- The activation of the regeneration of the particle emission filter
- Cutting off of the exhaust gas recirculation (EGR) function
Reference values
| minimal value | maximal value | |
|---|---|---|
| turbocharger pressure (absolute pressure) | - | 2,8 bars |
| turbo pressure at 3500 revs per minute (absolute pressure) | - | 2,45 bars |
| air flow measured at the flowmeter at idle (EGR valve closed) | 750 mg/stroke | 780 mg/stroke |
| opening of the inlet air metering unit at idle (EGR valve closed) | - | 5% |
Drift of the air flow sensor
The flowmeter drift is compensated by the engine ECU as a function of the richness value measured by the proportional lambda sensor
An excessive flowmeter drift causes the emission limits for the particles or pollutants, notably nitrous oxides (NOx), to be exceeded
The engine ECU calculates the flowmeter drift after each start-up
If the flowmeter drift is greater than 35%, a fault is reported
The following conditions allow the flowmeter drift to be calculated
- Exhaust gas recycling valve closed
- Supply of fuel cut off (driver foot off)
- Engine speed between 1400 and 2400 revs per minute
- Engine coolant temperature higher than 80°C
The engine ECU calculates the temperature of the air inside the cylinders as well as the total mass of air taken into the cylinders as a function of the following parameters
- Turbocharger pressure
- Atmospheric pressure
- Engine speed
- Air temperature at flowmeter
- Engine coolant temperature
The engine ECU compares the total mass of inlet air calculated with the total mass of inlet air measured by the flowmeter
When the difference between these 2 values is greater than 35%, a fault is reported
The following strategies are used in the event of a fault with the flowmeter
- Reduction of the turbo pressure via the control electrovalve of the turbocharger variable geometry actuator
- Reduction of the flow of fuel via the fuel flow regulation valve
- Cutting off of the exhaust gas recirculation (EGR) function
- Deactivation of the vehicle cruise control and speed limiter (according to model)
- The activation of the regeneration of the particle emission filter
- Lighting of the injection system fault warning lamp