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

Engine 264.9 in model 205, 253 

Function requirements, general 

• Engine runs

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 residues emitted by the engine.

The following are involved here:

• Nitrogen oxides (NO_x )
• Hydrocarbon (HC)
• Carbon monoxide (CO)
• Soot particles

The harmful constituents are reduced as follows:

• Reduction and oxidation in the three-way catalytic converter
• Filtration in gasoline particulate filter (with code 598 (Gasoline particulate filter (GPF) with sensor system) or code 961 (Exhaust system with GPF generation 2.0))
• Controlled exhaust gas recirculation

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 from approx. 400 to 800 °C.

To quickly reach this temperature, the switch points will be increased for max. 60 s in the case of a cold start (coolant temperature < 50 °C).

However, the upshift delay is only active up to a speed of 53 km/h.

An upshift of the gears therefore takes place only at higher engine speeds.

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) registers the wheel speed and transmits it via the suspension FlexRay (Flex E), the powertrain control unit (N127), and the 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:

• Sensor element of lambda sensor downstream of catalytic converter (G3/1 b1) (nitrogen oxide and oxygen concentration downstream of three-way catalytic converter)
• Sensor element of lambda sensor upstream of catalytic converter (G3/2b1) (nitrogen oxide and oxygen concentration upstream of three-way catalytic converter)
• Crankshaft Hall sensor (engine speed)

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

The oxygen stored during the "lean operating phase" is reduced totally or partially during the "rich operating phase". Aging reduces the three-way catalytic converter's oxygen storage capacity and thus its ability to convert carbon monoxide and hydrocarbons. 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.

The amplitudes of the lambda sensor signals upstream and downstream of the three-way catalytic converter are compared to do this. If both amplitudes are of an identical size, the three-way catalytic converter is no longer operational. Multiple measurements are performed in the lower partial-load range at the specified engine 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 [ME] control unit transmits the request via the drive CAN, the powertrain control unit, the suspension FlexRay, the electronic ignition lock control unit (N73), and the 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 diagnostic tester.

Exhaust gas cleaning in gasoline particulate filter (with code 598 (Gasoline particulate filter (GPF) with sensor system) or code 961 (Exhaust system with GPF generation 2.0)) 

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. Soot combustion takes place once there is sufficient oxygen 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. Excessively high temperatures during soot combustion can lead to damage to the entire gasoline particulate filter.

The exhaust gas temperature and the soot content of the gasoline particulate filter are permanently monitored. The exhaust gas temperature is registered by the temperature sensor upstream of the gasoline particulate filter (B163/4). The soot content is registered 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.

Reduction of pollutants via exhaust gas recirculation 

The occurrence of nitrogen oxides is reduced through exhaust gas recirculation into the combustion chamber.

This occurs via the retardation of the combustion. Temperature peaks that foster the occurrence of nitrogen oxides are avoided as a result.

The exhaust gas recirculation also contributes to a reduction in the charge change losses and thus also reduces the fuel consumption in the part load range.

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

External exhaust gas recirculation is carried out via a pipe installed outside of the engine that conducts the exhaust to the intake manifold. Internal exhaust gas recirculation is implemented through valve overlap, and thus the exhaust valves that are still open during the intake stroke.

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). The internal exhaust gas recirculation is regulated within certain limits.

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