S14.20-4574-79
Block diagram |
B1 | Engine oil temperature sensor | B37/4 | Accelerator pedal module | |
B2/6 | Left hot film mass air flow sensor | B60 | Exhaust pressure sensor | |
B2/6b1 | Left intake air temperature sensor | B70 | Crankshaft Hall sensor | |
B2/7 | Right hot film mass air flow sensor | M16/6 | Throttle valve actuator | |
B2/7b1 | Right intake air temperature sensor | N3/28 | CDI control unit | |
B5/1 | Boost pressure sensor | Y27/9 | Exhaust gas recirculation positioner (high-pressure circuit) | |
B11/4 | Coolant temperature sensor | Y85 | Exhaust gas recirculation cooler bypass switchover valve | |
B17/8 | Charge air temperature sensor | A | Mercedes-Benz | |
B19/11 | Temperature sensor upstream of turbocharger | B | Nissan | |
B28/5 | Pressure sensor downstream of air filter | C | Default | |
B28/8 | Differential pressure sensor (DPF) | D | Optional |
Exhaust gas recirculation function requirements - general
Circuit 87 (Engine management ON)
Engine running.
Engine in load range from neutral to the upper partial-load range
- Exhaust gas recirculation (EGR) - general
The EGR lowers the nitrogen oxide (NOx) portion in the exhaust gas. This occurs by means of the following 3 processes:
Reducing the oxygen concentration (O2) in the 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
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 temperature, engine load and engine rpm
Ambient conditions such as the air intake or the charge air temperature
Exhaust temperature
Diesel particulate filter status
Exhaust pressure
Time limitation (in idle)
Boost pressure
Coolant temperature
For this purpose, the CDI control unit reads in the (N3/28) following signals:
Engine oil temperature sensor (B1)
Left hot film mass air flow sensor (B2/6)
Left intake air temperature sensor (B2/6b1)
Right hot film mass air flow sensor (B2/7)
Right intake air temperature sensor (B2/7b1)
Boost pressure sensor (B5/1)
Coolant temperature sensor (B11/4)
Charge air temperature sensor (B17/8)
Pressure sensor downstream of air filter (B28/5)
DPF differential pressure sensor (B28/8)
Accelerator pedal module (B37/4)
Throttle valve actuator (M16/6)
Exhaust pressure sensor (B60)
Temperature sensor upstream of exhaust gas turbocharger (B19/11)
Crankshaft Hall sensor (B70)
After evaluation of the input signals, the CDI control unit, with the aid of the stored characteristics map of the exhaust gas recirculation positioner (high pressure circuit) (Y27/9), actuates with a pulse width modulated signal. The exhaust gas recirculation positioner (high pressure circuit) increases or decreases the amount of recycled exhaust gas led over a mixing tube downstream of the throttle valve actuator in the charge-air distributor according to actuation.
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.
The exhaust gas temperature determined by the temperature sensor upstream of the exhaust gas turbocharger (B19/11) is required by the CDI control unit to monitor the cooling function of the exhaust gas recirculation cooler.