EATU
A70 NOx sensor inlet of EATU B72 Exhaust temperature sensor
upstream of SCR catalytic converter
Function of the EATS (overall system)
The basic functionalities of the whole EATS are monitored and regulated over the engine management (MCM) control unit (A4) and the exhaust aftertreatment (ACM) control unit (A60). After an engine start the engine management (MCM) control unit (A4) starts an automatic test routine automatically in the background which checks the operational readiness of the EATS. The SCR control unit (A58) integrated in the pump module (1) is actuated after successful release of the system. This switches on the SCR delivery pump (M25) contained in the pump module (1) which now suctions up AdBlue“ out of the AdBlue“ container (5) and delivers it over the AdBlue“ feed line to the AdBlue“ metering device (A67).
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Since the AdBlue“ injection does take place continuously in the exhaust flow the AdBlue“ flows back again over the AdBlue“ return line into the AdBlue“ container. This circulation continuously takes place independently of whether AdBlue“ is injected or not. So recirculation cooling is achieved which protects the AdBlue“ metering device (A67) directly attached to the EATU (2) against damage due to overheating.
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Reduction of NOx in the SCR catalytic converter
The AdBlue“ injection into the exhaust flow is calculated by the engine management (MCM) control unit (A4). If AdBlue“ should be injected this first of all sends a signal to the exhaust
aftertreatment (ACM) control unit (A60) which processes the data and afterwards actuates the SCR control unit (A58) integrated on the pump module.
The injection timing point and the injection quantity are now calculated there and the AdBlue“ metering device (A67) is appropriately actuated.
The following occurs if AdBlue“ is injected:
the AdBlue“ metering device (A67) injects AdBlue“ into the so> called hydrolysis segment in the EATU (2) directly into the exhaust flow.
The AdBlue“ mixes here with the already precleaned exhaust and breaks down in a first process step into ammonia (NH3). Along
with the nitrogen oxide molecules (NOx) generated during combustion the ammonia (NH3) so created flows on in the exhaust
flow to the SCR catalytic converter (4). Its honeycomb structure has a special coating which allows conversion of NH3 and NOx into
W14.40>1592>79
AdBlue“/coolant line system
1 Pump module
6 Coolant feed line 7 Coolant return line
R7 AdBlue“ intake duct heating element
R8 AdBlue“ pressure line heating element
Y627 AdBlue“ heater coolant solenoid valve
A67 AdBlue“ metering device B74 AdBlue“ fill level
sensor/temperature sensor
R6 AdBlue“ return line heating element
AdBlue“ line system
The AdBlue“ line system lies between the AdBlue“ container (5), pump module (1) and AdBlue“ metering device (A67).
The fact that the AdBlue“ metering device (A67) is directly attached to the EATU and is therefore subjected to high temperatures, AdBlue“ is circulated continuously from engine start and in a certain run>on time after engine stop for recirculation cooling.
AdBlue“ heater
AdBlue“ freezes below a temperature of about >13∞C. The AdBlue“ heater ensures that any AdBlue“ that has frozen during periods of non>operation is heated and reliquified and prevents AdBlue from freezing while driving in cold outside temperatures. The AdBlue“ lines from the AdBlue“ container (5) to the pump module (1) are bundled with the coolant lines and routed insulated.
The AdBlue“ lines between the pump module (1) and the AdBlue“ metering device (A67) are not heated by coolant but instead over in electrically heated heating elements integrated in the line sections.
Function of AdBlue“ heating by coolant
The AdBlue“ heater consists of the AdBlue“ coolant solenoid valve heater (Y627) which is located on the rear side of the engine and a coolant line system. The AdBlue“ coolant solenoid valve heater (Y627) is actuated by the engine management (MCM) control unit (A4). Over the AdBlue“ fill level sensor/temperature sensor (B74) integrated in the AdBlue“ container (5), it detects when the temperature of the tank contents is approaching the defined limit value of approx. 8∞C. If this is the case and if the coolant temperature has already reached a temperature of 65∞C, the AdBlue“ heater coolant solenoid valve (Y627) is opened so the coolant flows through the line system.
Function of AdBlue“ heating by an electrical heater
The heating coil of the heating elements integrated in the AdBlue“ lines is switched on and off by the exhaust
aftertreatment (ACM) control unit (A60). Very pertinent here are also the values which are delivered by the AdBlue“ fill level sensor/temperature sensor (B74).
Overall network for exhaust aftertreatment
Page 79
Component description for engine management (MCM) control unit
A4
Page 103
Component description for NOx sensor outlet of EATU
A57, A57 b1
Page 110
Component description for pump module A58, M25
Page 115
Component description for exhaust aftertreatment (ACM) control unit
A60
Page 117
Component description for AdBlue metering device
A67
Page 121
Component description for NOx sensor control unit inlet of EATU
A70, A70 b1
Page 123
Component description for exhaust temperature sensor upstream of SCR catalytic converter
B72
Page 139
Component description for exhaust temperature sensor downstream of SCR catalytic converter
B73
Page 140
Component description for AdBlue“ fill level sensor/temperature sensor
B74
Page 142
Component description for AdBlue“ heater coolant solenoid valve
Y627
Page 180
Component description for AdBlue tank
Page 188
Component description for SCR catalytic converter
Page 209
GF14.40>W>0002H
Exhaust aftertreatment, function
20.7.11
ENGINE 471.9 in MODEL 963 with CODE (M5Z) Engine version Euro VI
General information
The EATS for fulfilling the Euro VI emissions standard is based on new engine technology in combination with a series of measures aimed at reducing exhaust emissions.