Exhaust Gas Recirculation, Function - GF14.20-P-3000MNG
ENGINE 276.9 in MODEL 166 as of model year 2016
with CODE 920 (Direct petrol injection with stratified charging)
Exhaust gas recirculation function requirements - general
- Circuit 87M (engine management ON)
- Engine in partial-load range
- Vehicle in motion
Exhaust gas recirculation, general
The exhaust gas recirculation lowers the combustion temperature during enrichment of the intake air with exhaust in stratified operation and in combined homogenous stratified operation, whereby the nitrogen oxide (NOx) development is reduced.
The NOx storage catalytic converters are loaded thereby more slowly with NOx and stratified operation is enabled for longer periods.
The exhaust gas recirculation quantity can be up to 30% of the intake air and is calculated on the basis of the following sensors and signals by the ME-SFI [ME] control unit (N3/10):
- Hot film MAF sensor (B2/5), exhaust gas recirculation rate
- Intake air temperature sensor (B2/5b1), intake manifold temperature
- Temperature sensor upstream of NOx storage catalytic converter on the right (B16), exhaust temperature
- Left temperature sensor upstream of NOx storage catalytic converter (B16/1), exhaust temperature
- Intake manifold intake air temperature sensor (B17/1), intake manifold temperature
- Pressure sensor downstream of throttle valve (B28/7), engine load
- Sensor elements of left and right oxygen sensors upstream of catalytic converter (G3/3b1, G3/4b1), residual oxygen content
- Sensor elements of left and right oxygen sensors downstream of catalytic converter (G3/5b1, G3/6b1), residual oxygen content
- Right and left NOx sensors (N37/6b1, N37/5b1), nitrogen oxide and oxygen components in the exhaust via the right and left NOx sensor control units (N37/6, N37/5) and the drive train sensor CAN (CAN I)
- Left and right exhaust gas recirculation valve Hall sensors (Y27/11 b1, Y27/12b1), position of the left and right exhaust gas recirculation valve rotary solenoids (Y27/11y1, Y27/12y1)
The exhaust gas recirculation valves are closed in homogeneous mode.
Function sequence for exhaust gas recirculation
The exhaust for exhaust gas recirculation is removed separately for each cylinder bank downstream of the three-way catalytic converter and led to the left and right exhaust gas recirculation valves (Y27/11, Y27/12) via the exhaust removal pipes. The volume of recirculated exhaust gas is regulated by the orifice cross-section of the respective exhaust gas recirculation valve.
To do this, the relevant exhaust gas recirculation valve rotary solenoid that actuates the exhaust gas recirculation valve is actuated by the ME-SFI [ME] control unit depending on a characteristics map by means of a pulse width modulated signal.
In order to keep the exhaust gas recirculation valve securely closed, the exhaust gas recirculation valve rotary solenoid is actuated with a duty cycle of about 15% and reverse polarity.
In a deenergized condition, the exhaust gas recirculation valve is held closed by a spring integrated in the moving magnet. The position of the exhaust gas recirculation valve rotary solenoid is recorded via the left or right exhaust gas recirculation valve Hall sensor and transmitted to the ME-SFI [ME] control unit for control and diagnosis.
Downstream of the exhaust gas recirculation valves, the exhaust flows together through a feed line towards the front into the intake manifold. The recirculated exhaust mixes with the fresh air intake there.
The exhaust gas recirculation valves are connected to the engine cooling circuit for cooling.
EGR diagnosis
If the ME-SFI [ME] control unit recognizes a non-closing exhaust gas recirculation valve the engine goes into limp-home mode.
A function test takes place for both exhaust gas recirculation valves shortly before the engine start and shortly after stopping the engine. To do this they are opened completely and then closed again. This test serves to reduce the tolerance and to increase the positioning accuracy.
Design of the exhaust gas recirculation system
| Electrical function schematic for exhaust gas recirculation | PE14.20-P-2052-97NBG | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNG |