GF14.40-D-0002HU Exhaust Aftertreatment, Function
GF14.40-D-0002HU Exhaust Aftertreatment, Function
- with CODE (MG5) Engine OM 642 DE 30 LA, 140 kW (190 hp) 3800 rpm
- with CODE (MH1) Low-emission engine EPA 10/CARB
- with CODE (ZU7) National version for Canada
- with CODE (MG5) Engine OM 642 DE 30 LA, 140 kW (190 hp) 3800 rpm
- with CODE (MH1) Low-emission engine EPA 10/CARB
- with CODE (ZU8) National version for USA
A1 Instrument cluster
A1p1 Display
A1e41 "CHECK ENGINE" MIL
A97/1 Control unit for NOx sensor upstream of SCR catalytic converter
A97/2 Control unit for NOx sensor downstream of SCR catalytic converter
B16/11 Temperature sensor upstream of turbocharger
B16/12 Temperature sensor upstream of SCR catalytic converter
B19/18 Temperature sensor upstream of CAT
B19/19 Temperature sensor upstream of diesel particulate filter
B28/20 Diesel particulate filter differential pressure sensor
B85/3 Oxygen sensor
B151 AdBlue(R) pressure sensor
B152 AdBlue(R) tank fill level sensor
M89 AdBlue(R) delivery pump
M89r1 AdBlue(R) delivery pump heating element
N3/30 CDI control unit
N14/3 Glow output stage
N15/3 ETC control unit (with transmission 722.6)
N141 AdBlue(R) control unit
R9/1 Cylinder 1 glow plug
R9/2 Cylinder 2 glow plug
R9/3 Cylinder 3 glow plug
R9/4 Cylinder 4 glow plug
R9/5 Cylinder 5 glow plug
R9/6 Cylinder 6 glow plug
R51 AdBlue(R) tank heating element
R51b1 AdBlue(R) tank temperature sensor
R52 AdBlue(R) injection line heating element
Y76/18 Cylinder 1 injector
Y76/19 Cylinder 2 injector
Y76/20 Cylinder 3 injector
Y76/21 Cylinder 4 injector
Y76/22 Cylinder 5 injector
Y76/23 Cylinder 6 injector
Y129 AdBlue(R) switchover valve
Y130 AdBlue (R) injection valve
CAN C Engine compartment CAN
CAN I Drive train sensor CAN
LIN C1 Drive train LIN
Function requirements for exhaust aftertreatment, general points
^ Circuit 87 ON (engine control ON)
^ Engine running
Exhaust aftertreatment, general points
The task of the exhaust aftertreatment is to reduce the exhaust emissions:
- Nitrous oxide (NOx)
- Hydrocarbons
- Carbon monoxide (CO)
- Soot particle
All exhaust gas relevant functions and components are monitored by the OBD. The OBD is integrated in the CDI control unit.
Pollutant reduction is supported by the following partial function:
- Intake port shutoff (EKAS)
- Diesel particulate filter (DPF) preheating
- Exhaust gas recirculation (EGR)
- Injection of AdBlue(R) reducing agent
The CDI control unit reads in the following sensors directly:
- Temperature sensor upstream of SCR catalytic converter
- Temperature sensor upstream of CAT
- Temperature sensor upstream of diesel particulate filter
- Temperature sensor upstream of turbocharger
- Diesel particulate filter differential pressure sensor
- Oxygen sensor
The following information is read in by the CDI control unit via the drive train sensor CAN:
- from the AdBlue(R) control unit, the injected quantity of reducing agent (for NOx reduction and the fill level in the AdBlue(R) tank in the case of cooling of the AdBlue(R) injection valve
- from the NOx sensor control unit upstream of SCR CAT and from the NOx sensor control unit downstream of SCR CAT, the NOx and the oxygen concentration in the exhaust Exhaust aftertreatment, function sequence
The following subsystems are involved in exhaust aftertreatment:
^ Function sequence for oxidation catalytic converter
^ Function sequence for DPF
^ Function sequence for Selective Catalytic Reduction (SCR) catalytic converter
Function sequence for oxidation catalytic converter
The oxicat ensures lowering of the hydrocarbon, CO and NOx and generates the required thermal energy for the DPF regeneration phase by means of afterburning.
Function sequence for DPF
The diesel particulate filter consists of a ceramic honeycomb filter body out of silicon carbide, which is coated with rare metal platinum. The passages of the diesel particulate filter are opened alternatively at the front and rear and are separated from each other through the porous filter walls of the honeycomb filter body.
The precleaned exhaust which has passed though the oxidation catalytic converter flows into the ducts of the DPF which are open to the front at the front and passes through the porous filter walls of the honeycomb filter body into the ducts which are open to the rear.
After this, the cleaned and filtered exhaust is dissipated through the exhaust system. The soot particles are retained in the honeycomb filter body of the DPF.
If the soot particle content exceeds a map-dependent value, the CDI control unit starts the regeneration phase under the given regeneration conditions. The CDI control unit receives the soot particle content in the DPF via the DPF differential pressure sensor.
Regeneration takes place via a periodical increase of the exhaust temperature. For this purpose, the following functions are taken over by the CDI control unit:
- One further post injection over the cylinder 1 injector, the cylinder 2 injector, the cylinder 3 injector, the cylinder 4 injector, the cylinder 5 injector, the cylinder 6 injector
- DPF glow function over the drivetrain LIN, the glow time output stage by the cylinder 1 glow plug, the cylinder 2 glow plug, the cylinder 3 glow plug, the cylinder 4 glow plug, the cylinder 5 glow plug, the cylinder 6 glow plug
- The shift line displacement over the engine compartment CAN by the EGS control unit (with transmission 722.6)
Reduction of the soot portion is approx. 99%.
By increasing the exhaust temperature, the soot particles retained in the DPF are mostly burnt off to produce carbon dioxide (CO 2). The ash produced remains in the DPF.
During the regeneration, the exhaust temperature is monitored by the temperature sensor upstream of the turbocharger and the temperature sensor upstream of the diesel particulate filter.
Through the exhaust gas pressure lines upstream and downstream of the DPF, the DPF differential pressure sensor determines the pressure differential between the exhaust gas pressure upstream and downstream of the DPF.
The soot particle content in the DPF is determined using a performance map on the basis of the pressure differential and the exhaust mass calculated by the CDI control unit.
Necessary maintenance of the DPF is signalized via the CHECK ENGINE indicator lamp in the IC.
On short trips, regeneration is interrupted and distributed over several driving cycles. Until the specified regeneration temperature is reached several heating-up phases are required.
Regeneration occurs unnoticeably by the customer.
Function sequence for SCR catalytic converter
The AdBlue(R) reducing agent is injected upstream of the SCR catalytic converter, and is converted to ammonia through thermal decomposition (heat-induced chemical reaction ) and hydrolysis (water-induced chemical reaction). There is a mixing element between the AdBlue(R) injection valve and the SCR catalytic converter. This serves to achieve improved hydrolysis and even distribution of the AdBlue reducing agent upstream of the SCR catalytic converter. In the SCR catalytic converter, the NOx contained in the exhaust gas is converted with the ammonia into nitrogen (N 2) and water molecules. The required amount of reducing agent is calculated according to a performance map by the CDI control unit and sent via the CAN drive train sensor to the AdBlue reducing agent. This control unit then initiates map-controlled injection of the calculated quantity of AdBlue(R) reducing agent through the AdBlue(R) injection valve.
The conversion rate of the NOx portion in the exhaust is about 80%.
If the "Reserve" fill level in the AdBlue(R) tank is reached, the driver is informed parallel to an audible signal over the display in the IC that he should find a workshop and have the required maintenance work done.
If the "Empty" fill level is reached in the AdBlue(R) tank, a plausibility check on the "Empty" fill level is carried out using a computer model. If the plausibility check also results in an "empty" fill level, an audible signal is given, an entry is made in the fault memory of the control unit (CDI), and there is actuation of the CHECK ENGINE indicator lamp in the IC. The driver then has up to 20 engine starts available, with an assumed trip distance of 32 kilometers or 20 miles in each case. The number of the still available starts is displayed in the instrument cluster. The vehicle can no longer be started after the last remaining "Start".
