Exhaust Gas Recirculation, Function - GF14.20-P-3000MMG
ENGINE 276.9 in MODEL 166 up to 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 homogeneous 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
- Left and right oxygen sensors upstream of catalytic converter (G3/3, G3/4), residual oxygen content
- Left and right oxygen sensors downstream of catalytic converter (G3/5, G3/6), 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)
- Right and left exhaust gas recirculation Hall sensors (Y87/1 b1, Y87/2b1), positions of the right and left exhaust gas recirculation actuator motors (Y87/1 m1, Y87/2m1)
The exhaust gas recirculation valves are closed in homogeneous mode.
Function sequence for exhaust gas recirculation
The exhaust for the EGR is taken downstream of both firewall catalytic converters and led over exhaust removal pipes to the exhaust recycle housing.
The exhaust gas recirculation rate is controlled by the exhaust gas recirculation valves. To do this the right and left EGR actuator motors which actuate the exhaust gas recirculation valves are actuated by the ME-SFI [ME] control unit by means of a pulse width modulated signal (PWM signal) according to the engine load. In order to securely hold the exhaust gas recirculation valves closed the RH and LH EGR actuator motors are actuated with a duty cycle of about 15% and reversed polarity. They are held closed by spring force in an deenergized condition.
The position of the respective exhaust gas recirculation valve is detected over the RH and LH EGR Hall sensors and transmitted to the ME-SFI [ME] control unit for control and diagnosis.
After the exhaust recycle housing the exhaust flows together through a pipe to the front in the intake manifold. The recirculated exhaust mixes with the fresh air intake there.
The exhaust gas recirculation valves, the EGR actuator motors on the right and left and the EGR Hall sensors on the right and left are brought together for both cylinder heads in the exhaust recycle housing. This is connected for cooling to the engine cooling circuit.
Diagnosis of the EGR system
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-2052-97NAE | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MMG |