Exhaust gas recirculation, function - GF14.20-P-3000OM

ENGINE 651.9 in MODEL 204 (except 204.9), 204.9 up to 5/31/12, 207, 212.0 (except 212.098), 212.2 (except 212.298), 218 

Function requirements for exhaust gas recirculation (EGR), general points 

• Circuit 87M ON (Engine management ON)
• Engine runs
• Engine in load range from neutral to the upper partial-load range

Exhaust gas recirculation, general 

The EGR lowers the nitrogen oxide (NOx) portion in the exhaust. This occurs by means of the following 3 processes:

• Reduction of oxygen (O₂ ) concentration in combustion chamber
• Reduction of the combustion temperature through reduction of the combustion speed
• Reduction of the combustion temperature through a higher heat capacity of the recirculated exhaust compared to the intake air

Heat capacity

The heat capacity is a material property and indicates how much heat a substance can store per temperature change.

Function sequence for exhaust gas recirculation 

EGR is active from idle through to the upper partial-load range. Determination of the EGR rate takes place depending on the following variables:

• Engine load and engine rpm, engine temperature
• Intake and charge air temperature
• Exhaust temperature and exhaust pressure
• Diesel particulate filter status (with code (474) Particulate filter)
• Boost pressure
• Coolant temperature
• Time limitation

For this purpose, the CDI control unit (N3/9) reads signals from the following components:

• Hot film MAF sensor (B2/5)
• Intake air temperature sensor (B2/5b1) (model 204, 207, 212), intake air temperature sensor (B2/5b1) (model 218)
• Boost pressure sensor (B5/1)
• Boost pressure sensor for low-pressure turbocharger (B5/4) (except engine 651.913/925.)
• Exhaust gas recirculation temperature sensor (B16/14) (with code (494) USA version)
• Charge air temperature sensor (B17/8)
• Temperature sensor upstream of CAT (B19/7) (with code U42 (BlueTEC (SCR) diesel exhaust treatment)) (except model 204.0/2/3, 207, 218) or (with code U77 (BlueTEC (SCR) diesel exhaust treatment)) and (with code 494 (USA version)) as of 01.09.13 (except model 204.0/2/3 model 207, model 218) or (with code U77 (BlueTEC (SCR) diesel exhaust treatment)) as of 01.09.14 (except model 204.0/2/3)
• Temperature sensor upstream of diesel particulate filter (B19/9) (with code 474 (Particulate filter))
• Temperature sensor upstream of turbocharger (B19/11)
• Exhaust gas recirculation cooling bypass flap Hall sensor (B90) (with code (494) USA version)
• Pressure sensor downstream of air filter (B28/5)
• DPF differential pressure sensor (B28/8) (with code 474 (Particulate filter))
• DPF differential pressure sensor for OBD (B28/16) (with code U42 (BlueTEC (SCR) diesel exhaust treatment)) (except model 204.0/2/3, 207, 218) and (with code (494) USA version))
• Accelerator pedal sensor (B37)
• Exhaust pressure sensor (B60)
• Crankshaft Hall sensor (B70) (with code B03 (ECO start/stop function))
• Crankshaft position sensor (L5) (except code B03 (ECO start/stop function))
• Actual value potentiometer 1 (M16/6r1), throttle valve

After evaluating the input signals, the CDI control unit uses a stored characteristics map to actuate the exhaust gas recirculation actuator (Y27/9) by means of a pulse width modulation (PWM) signal.

Depending on its actuation, the exhaust gas recirculation actuator increases or decreases the quantity of recirculated exhaust which is led into the charge air distributor via a mixing tube downstream of the throttle valve actuator (M16/6).

To increase the effect of EGR, the exhaust gas is passed through the exhaust gas recirculation cooler where it is cooled.

If the temperature of the recirculated exhaust gas is too low, the recirculated exhaust gas can be guided past the exhaust gas recirculation cooler via a bypass duct.

If the exhaust gas recirculation cooler bypass switchover valve (Y85) is actuated by the CDI control unit by means of a ground signal based on a characteristics map, then the vacuum stored in the vacuum reservoir acts on the exhaust gas recirculation cooler bypass vacuum unit and opens the bypass in the exhaust gas recirculation cooler via a linkage.

ENGINE 651.9 in MODEL 207 as of 9/1/14, 212 (except 212.098/298) as of 9/1/14, 218 as of 9/1/14

with CODE U77 (Diesel Emission control BLUETEC (SCR))

without CODE 494 (US version)

without CODE U42 (BlueTEC diesel exhaust treatment (SCR))

ENGINE 651.9 in MODEL 212 (except 212.098/298) as of 9/1/13

with CODE 494 (US version)

with CODE U77 (Diesel Emission control BLUETEC (SCR))

without CODE U42 (BlueTEC diesel exhaust treatment (SCR))

ENGINE 651.9 in MODEL 212 (except 212.098/298)

with CODE U42 (BlueTEC diesel exhaust treatment (SCR))

These vehicles fulfill the EU6 exhaust emissions standard and the USA BIN5 exhaust emissions standard.