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Exhaust Treatment Function - GF14.00-P-3000OGF

Engine 642.8 in model 166 as of model year 2016 

Engine 642.8 in model 292 

Function requirements, general 

IMPORTANT The CDI control unit (N3/9) detects engine running by evaluating the signals of the crankshaft Hall sensor (B70). The CDI control unit directly reads in the signals of the crankshaft Hall sensor.

Exhaust treatment, general 

The exhaust gas cleaning reduces the harmful components of the combustion gases and residues emitted by the engine.

The following are involved here:

Pollutant reduction is supported by the following functions:

The CDI control unit processes the signals of the sensors for this purpose:

Exhaust gas cleaning in diesel oxidation catalytic converter 

The diesel oxidation catalytic converter contributes via reduction and oxidation to a reduction in the hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxide (NOx ). The thermal energy required for the DPF regeneration phase is generated via an afterburning.

Exhaust gas cleaning in DPF 

The diesel particulate filter consists of a ceramic honeycomb filter body made out of silicon carbide, which is coated with rare metal platinum. The passages of the diesel particulate filter are opened alternately at the front and rear and are separated from each other through the porous filter walls of the honeycomb filter body. The exhaust gas flows into the DPF channels that open to the front. It subsequently flows through the porous filter walls of the honeycomb filter body into the channels that open to the rear. The exhaust gas is then dissipated by the exhaust system. The soot particles are retained in the honeycomb filter body of the DPF.

If the soot content exceeds a specific value, the CDI control unit initiates the regeneration phase. The CDI control unit calculates the soot content in the DPF by evaluating the signals of the DPF differential pressure sensor.

The exhaust temperature is periodically increased for the regeneration phase. For this purpose, the CDI control unit starts the following actions:

The CDI control unit transmits the shift line offset request via the drive CAN (CAN C) to the fully integrated transmission control unit (Y3/8n4).

By increasing the exhaust gas temperature, the soot particulates deposited in the DPF are mainly burnt to produce carbon dioxide (CO2) . The ash produced remains in the DPF. The exhaust gas temperature is detected during regeneration by the temperature sensor upstream of the exhaust gas turbocharger and by the temperature sensor upstream of the diesel particulate filter.

If the DPF needs to be maintained, the engine diagnosis indicator lamp (A1e58) in the instrument cluster (A1) lights up. The CDI control unit transmits the request to actuate the engine diagnosis indicator lamp via the drive CAN, powertrain control unit, suspension FlexRay, electronic ignition lock control unit and user interface CAN (CAN HMI) to the instrument cluster.

IMPORTANT On short-distance trips, regeneration is interrupted and distributed over several driving cycles. The heating phases until the required regeneration temperature is reached become more frequent as a result. Regeneration occurs unnoticeably for the customer.

Exhaust gas cleaning in SCR catalytic converter (with code U77 (BlueTEC (SCR) diesel exhaust gas cleaning)) 

The AdBlue® reduction agent that is converted into ammonia (NH3) via thermolysis (heat-induced chemical reaction) and hydrolysis (water-induced chemical reaction) is injected upstream of the SCR catalytic converter.

There is a mixing element between the AdBlue® metering valve (Y129) and the SCR catalytic converter. It ensures an improved hydrolysis and a more even distribution of the AdBlue® reduction agent upstream of the SCR catalytic converter. In the SCR catalytic converter, the NOx contained in the exhaust is converted in the SCR catalytic converter together with the NH3 into molecular nitrogen (N2 ) and water H2 O.

The CDI control unit calculates the required reduction agent quantity and supplies this via the drive train sensor CAN to the AdBlue® control unit (N118/5). The AdBlue® control unit then accordingly actuates the AdBlue® metering valve.

The NOx sensors monitor the NOx concentration in the exhaust gas. The NOx sensors are heated so that they quickly reach their operating temperature. The CDI control unit transmits the heating request via the drive train sensor CAN to the NOx sensor control units. The NOx sensor control units then actuate the heating elements of the NOx sensors.

IMPORTANT The conversion rate of the NOx content in the exhaust gas lies at approx. 10 %. The reduction in the soot content present is about 99 %.

IMPORTANT If the fill level "Reserve" has been reached in the AdBlue® tank, a message appears in the instrument cluster. This message contains the request to visit a workshop and have maintenance performed. An acoustic signal is also output.

IMPORTANT If the AdBlue® tank is empty, the engine diagnosis indicator lamp in the instrument cluster lights up. The CDI control unit checks the plausibility of this status and stores a fault in the fault memory.

The driver then has up to 20 engine starts available, with an assumed trip distance of 32 kilometers in each case. The number of standing starts is displayed in the instrument cluster. The vehicle can no longer be started after the last remaining "Start".

EKAS 

Under all engine load conditions, the intake port shutoff tries to obtain the best possible relation between air turbulence and air mass.

The CDI control unit also reads in the signals of the following sensors for the implementation of the intake port shutoff:

The CDI control unit evaluates the incoming information and actuates the inlet port shut-off positioning motor (M55) in a pulse width modulated manner. In the lower engine speed and engine load range, half of the intake ports (2 intake ports available per cylinder) are closed by flaps. The flow velocity increases in the open intake ports. This leads to a higher swirl which creates a better vortex. The combustion optimized as a result leads, among other things, to a reduction of the soot particles in the exhaust gas.

With increasing engine speed and engine load, the closed intake ports are continuously reopened. The best possible ratio between air swirl and air mass thus exists for every engine operating phase.

IMPORTANT In the case of a fault or interruption in the supply voltage, the flaps are kept open or closed by spring force.

  Electrical function schematic for exhaust treatment   PE14.00-P-2051-97NBD 
  Overview of system components for common rail diesel injection (CDI)   GF07.16-P-9997OGF
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