LEMON Manuals: Even more car manuals for everyone
Home >> Mercedes Benz >> 2017 >> E300 Base >> Repair and Diagnosis >> Engine Mechanical >> Mechanical >> Exhaust Manifolds, Emission Control System - 213 Chassis >> Basic Knowledge >> Exhaust Treatment Function >> Exhaust Treatment Function - GF14.00-P-3000MRD

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

Engine 274.9 in model 213, 238 

up to model year 2021 

Function requirements, general 

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 

The exhaust gas cleaning reduces the harmful components of the combustion gases and combustion residues emitted by the engine. The following are involved here:

Exhaust gas cleaning is performed by means of:

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 of the automatic transmission are increased for a maximum of 60 s during a cold start (coolant temperature < 50°C). However, upshift delay is active only up to a speed of 53 km/h.

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

The ME-SFI [ME] control unit transmits the request for the upshift delay via the drive CAN (CAN C1) to the fully integrated transmission control unit (Y3/8n4) depending on the wheel speed and the coolant temperature.

The Electronic Stability Program control unit (N30/4) records the wheel speed and transmits it via the suspension FlexRay (Flex E), powertrain control unit (N127) and drive CAN to the ME-SFI [ME] control unit.

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

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

Through oxidation, carbon monoxide is converted to carbon dioxide (CO2 ), and hydrocarbon is converted to water (H2 O) and carbon dioxide.

Through reduction, the nitrogen oxides are converted to nitrogen (N2 ) and carbon dioxide.

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 The oxygen stored during the "lean operating phase" is reduced totally or partially during the "rich operating phase". As a result of aging, the oxygen storage capacity of the three-way catalytic converter, and thus its ability to convert carbon monoxide and hydrocarbons, is reduced. Due to the three-way catalytic converter's high oxygen storage capacity, the change in oxygen content is nearly fully dampened downstream of the three-way catalytic converter.

Consequently, the oxygen sensor signal downstream of the three-way catalytic converter has a low amplitude and is virtually constant.

To do so, the amplitudes of the lambda sensor signals upstream and downstream of the three-way catalytic converter are compared. If both amplitudes are the same, the three-way catalytic converter is no longer operational. Multiple measurements are performed in the lower partial-load range at specified rotational speeds, and the results are compared with a characteristics map in the ME-SFI [ME] control unit.

Where a defect is detected, a fault message is output in the instrument cluster (A1). The ME-SFI [ME] control unit transmits the corresponding request via the drive CAN, powertrain control unit, suspension FlexRay, electronic ignition lock control unit (N73) and user interface CAN (CAN HMI) to the instrument cluster.

Any faults detected are stored in the 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 the oxygen is available in the gasoline particulate filter.

The thermal load of the gasoline particulate filter in overrun mode is primarily dependent on the soot content and the exhaust gas temperature upstream of the gasoline particulate filter. If the temperatures during soot combustion are too high, this may cause damage to the entire gasoline particulate filter. In order to prevent this from happening, the exhaust gas temperature and the soot content in the gasoline particulate filter are monitored permanently.

The exhaust gas temperature is recorded by the temperature sensor upstream of the gasoline particulate filter (B163/4). The soot content is recorded by the gasoline particulate filter differential pressure sensor (B163/3). 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.

Exhaust gas cleaning in the NOx storage catalytic converter (with code 920 (Gasoline direct injection with stratified charge)) 

In homogeneous mode with λ = 1 the pollutants hydrocarbon, carbon monoxide and nitrogen oxide are converted in the three-way catalytic converter.

In stratified charge operation with λ > 1, the level of nitrogen oxide increases and the conversion of the nitrogen oxide is taken over by the NOx storage catalytic converter. It stores the nitrogen oxides through chemical binding. When the storage capacity is exhausted, the stored nitrogen oxide is converted into nitrogen and carbon dioxide by purging the NOx storage catalytic converter.

Purging of NO x  storage catalytic converter 

The fuel-saving stratified operation can only be enabled when the increasing amounts of nitrogen oxides in the NOx storage catalytic converter have been converted.

In order to purge the NOx storage catalytic converter, the ME-SFI [ME] control unit evaluates the signals from the following sensors:

The ME-SFI [ME] control unit detects that the NO x storage catalytic converter is full via an abrupt increase in the NOx . Homogeneous operation is activated as a reaction to this and the mixture enriched, so that the NOx storage catalytic converter can regenerate. Stratified operation is then activated again.

For the NOx conversion is a temperature range of 250 to 500°C in the NOx storage catalytic converter is optimal. For stratified charge operation or full load, the temperature must not exceed approx. 850°C.

The exhaust gas temperature is recorded by the temperature sensor upstream of the NOx storage catalytic converter. The ME-SFI control unit reads in the signals from the temperature sensor upstream of the NOx storage catalytic converter directly.

Mixture formation is used to regulate the temperature of the NOx storage catalytic converter. The mixture formation is adapted on the basis of the stored temperature models in order to protect the NOx storage catalytic converter against excessively high temperatures.

IMPORTANT In order to convert all pollutants in the exhaust, sulfur-free fuel is required. Sulfur blocks the spaces for nitrogen oxides in the NOx storage catalytic converter, resulting in fewer nitrogen oxides being stored. Stratified operation is therefore shortened and purging must be performed more frequently.

Reduction of pollutants by means of exhaust gas recirculation 

Exhaust gas recirculation into the combustion chamber reduces the formation of nitrogen oxide.

This is done by slowing down the combustion and thereby preventing temperature peaks that favor the formation of nitrogen oxide.

Exhaust gas recirculation also contributes to reducing charge change loss and thus also reduces fuel consumption in the partial-load range.

A distinction is made between external and internal exhaust gas recirculation.

In the case of external exhaust gas recirculation, the exhaust is recirculated to the intake manifold via a pipe.

Internal exhaust gas recirculation is implemented by means of valve overlap and thus through exhaust valves that are still open during the intake stroke.

IMPORTANT The ME-SFI [ME] control unit determines the valve overlap by actuating the intake camshaft adjustment solenoid (Y49/1) and the exhaust camshaft adjustment solenoid (Y49/2). Internal exhaust gas recirculation is thereby regulated within certain limits.

  Electrical function schematic for exhaust treatment   PE14.00-P-2051-97DBD 
  Overview of system components for gasoline injection and ignition system with direct injection Engine 274.9 in model 213 (except 213.050/053/153), 238
up to model year 2021		 GF07.70-P-9998MRD
    Engine 274.9 in model 213.050/053/153 up to model year 2021 GF07.70-P-9998MRP
scientia non olet · About LEMON Manuals