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

Engine 178.9 in model 190 

Function requirements for exhaust treatment, general points 

IMPORTANT The ME-SFI [ME] control unit (N3/10) detects the engine running via the evaluation of the crankshaft Hall sensor signals (B70). The ME-SFI [ME] 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:

The reduction of harmful components is achieved through reduction and oxidation in the three-way catalytic converter and filtration in the gasoline particulate filter (with code 598 (gasoline particulate filter (OPF) with sensor system)).

Exhaust gas cleaning in three-way catalytic converter 

For a three-way catalytic converter, the operating temperature is decisive. Significant pollutant conversion only begins from an operating temperature of about 250°C.

Ideal operating conditions for high conversion rates and a long service life exist in the temperature range between approx. 400 and 800°C.

To reach this temperature quickly, the switch points are increased for a maximum of 60 s during a cold start (coolant temperature < 35°C). However, upshift delay is active only up to a speed of 40 km/h.

The gears are therefore not shifted up until higher rotational speeds are reached.

Depending on the coolant temperature and wheel speed, the ME-SFI control unit transmits the upshift delay to the dual-clutch transmission control unit (N15/13). via the drive CAN (CAN C1).

The ME-SFI [ME] control unit reads in the signals of the coolant temperature sensor (B11/4) directly.

The Electronic Stability Program control unit (N30/4) transmits the wheel speed to the ME-SFI control unit via suspension CAN 1 (CAN E1), the powertrain control unit (N127), and the drive CAN.

The chemical conversion takes place in the three-way catalytic converter at λ = 1.

Through oxidation, the carbon monoxide (CO) is converted into carbon dioxide (CO2 ) and the hydrocarbon (HC) into water (H2 O) and carbon dioxide (CO2 ).

Through reduction, the nitrogen oxide (NOx ) is converted into nitrogen (N2 ) and carbon dioxide (CO2 ).

Once the operating temperature is reached and lambda control has been enabled, the function of the three-way catalytic converter is monitored by the ME-SFI [ME] control unit.

For this purpose, the ME-SFI [ME] control unit reads in the signals from the following component parts:

The ME-SFI [ME] control unit assesses the oxygen storage capacity of the three-way catalytic converter and, with that, assesses its aging.

IMPORTANT Any oxygen exceeding the amount required for the three-way catalytic converter to oxidize carbon monoxide (CO) is stored.

If the oxygen present in the exhaust gas is not sufficient for oxidizing the carbon monoxide (CO), the stored oxygen is fully or partially removed. In combination with the high oxygen storage capacity of the three-way catalytic converter, this procedure achieves an almost complete compensation for the fluctuations in oxygen concentration upstream of the three-way catalytic converter. The oxygen storage capacity, and thus the function of the three-way catalytic converter, can be assessed on the basis of the lambda sensor signals upstream and downstream of the three-way catalytic converter. In the case of a fully functional three-way catalytic converter, high values and changes are measured upstream and downstream of the three-way catalytic converter. In contrast, the lambda sensor signal downstream of the three-way catalytic converter is virtually constant. As the aging process advances, the oxygen storage capacity of the three-way catalytic converter, and thus its ability to convert carbon monoxide (CO) and hydrocarbons (HC), is reduced. Consequently, the lambda sensor signal downstream of the three-way catalytic converter becomes increasingly similar to the lambda sensor signal upstream of the three-way catalytic converter.

The lambda sensor signals upstream and downstream of the three-way catalytic converter are compared. If both signals are almost identical, the three-way catalytic converter is no longer operational. Several measurements are carried out in the lower partial-load range for specified rotation speeds. The results are compared with a characteristics map in the ME-SFI control unit.

Where a defect is detected, a fault message is output in the instrument cluster (A1). The ME-SFI control unit transmits the request for the actuation of the engine diagnosis indicator lamp (A1e58) to the instrument cluster via the drive CAN, powertrain control unit, suspension CAN 1, AMG gateway control unit (N93/9), and the user interface CAN (CAN HMI). Recognized fault are stored in fault memory of the ME-SFI [ME] control unit. These can be read out and deleted with the vehicle diagnosis system.

Exhaust gas cleaning in the gasoline particulate filter (with code 598 (gasoline particulate filter (OPF) with sensor system)) 

The gasoline particulate filter absorbs the emitted soot particles and regenerates itself under specific operating conditions.

The regeneration (soot combustion) of the gasoline particulate filter takes place while the vehicle is being operated in a conventional driving style, predominantly in overrun mode. The soot combustion takes place as soon as enough oxygen is available in the gasoline particulate filter.

The soot content of the gasoline particulate filter is monitored constantly.

The soot content is determined via the left gasoline particulate filter differential pressure sensor (B163/5) and the right gasoline particulate filter differential pressure sensor (B163/6). The ME-SFI [ME] control unit reads the sensor signals in directly and evaluates them. If the measured values exceed specific limits, the ME-SFI [ME] control unit initiates appropriate interventions in the engine timing and requests a warning message in instrument cluster.

  Electrical function schematic for exhaust treatment   PE14.00-P-2051-97HBA 
  Overview of system components for gasoline injection and ignition system with direct injection   GF07.70-P-9998MNB
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