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12-24-2007, 08:19 PM
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Cummins 6.7L DIESEL PARTICULATE FILTER (DPF)and Diesel Oxidation Catalyst (DOC)
DIESEL PARTICULATE FILTER
DESCRIPTION DIESEL OXIDATION CATALYST (DOC) The Diesel Oxidation Catalyst (DOC) is a ceramic flow through substrate coated with a catalyst washcoat that is integral to the DOC assembly. The close coupled DOC treats engine exhaust gases by converting harmful carbon monoxide, unburned hydrocarbons and other compounds into water, carbon dioxide and heat. Pick-up vehicles use a separate DOC assembly. Cab-Chassis vehicles use a combination Diesel Oxidation Catalyst/Diesel Particulate Filter (DOC/DPF) DIESEL PARTICULATE FILTER The Diesel Particulate Filter (DPF) is a wall-pass ceramic filter substrate coated with a catalyst washcoat that is integral to the DOC/DPF assembly. The partially treated exhaust gases from the DOC, flow into the catalyzed diesel particulate filter (DPF) which traps and accumulates particulate matter and further treats the exhaust gases to reduce unburned hydrocarbons and other harmful compounds. the trapped particulate molecules will be periodically removed from the DPF via a thermal regeneration process initiated by the engine's electronic control module (ECM). OPERATION The oxidation catalyst raises the exhaust gas temperatures to regenerate the DPF, which is passive regeneration. If the passive regeneration cannot keep up with the build up of soot in the DPF, the ECM will actively regenerate the DPF to burn off the soot. Residue remains inside the DPF in the form of non burnable ash. Ash comes from the oils and other materials that are trapped in the oils and are present in the soot. The catalyst contains a large number of parallel channels, which run in the axial direction and are separated by thin porous walls. The channels are alternatively open at one end, but plugged at the other. The exhaust gases flow through the walls and escape through the pores in the wall material. Particulates, however, are too large to escape and are trapped in the monolith walls. The ECM starts the regeneration of the DPF if the soot load exceeds a performance map value. The ECM determines the load condition of the DPF based upon the exhaust gas pressure upstream and downstream of the DPC/DPF. A pressure differential sensor provides the pressure input to the ECM. During the regeneration process, the ECM raises the temperature in the DOC/DPF to burn off the soot accumulated. Under normal operation, the engine does not produce enough heat to oxidize the soot inside the DOC/DPF. This process requires temperatures above 550 ºC (1,022 ºF). After regeneration, the ECM reads the actual pressure difference at the DOC/DPF and compares it with a reference value. From this comparison, the ECM determines the ash quantity inside the DOC/DPF. DIESEL PARTICULATE FILTER EVIC Message Center - Message - Catalyst Full The engine Electronic Control Module (ECM) monitors the soot load in the diesel particulate filter. Under normal operating conditions the diesel particulate filter is self-cleaning, where accumulated soot is converted to ash. Under light load operating conditions, the driver may be notified via the vehicle's Electronic Vehicle Information Center (EVIC) message center "CATALYST FULL: SEE OWNERS MAN" message will be displayed indicating that it is necessary to modify the vehicles driving routine/duty-cycle in order to allow the diesel particulate filter system to self clean. If the vehicle's EVIC message center notification is ignored, the vehicle will eventually derate the engine and set a fault, requiring service. The soot load in the diesel particulate filter is estimated by the ECM using the Exhaust Pressure Sensor values and the calculated soot output of the engine. This fault code will be triggered if the application is not operating at a duty cycle high enough to allow active regeneration of the diesel particulate filter. This fault code is an indication that the exhaust temperatures exiting the turbocharger are not high enough to allow active regeneration of the soot that is trapped in the diesel particulate filter. It may be necessary to increase the duty cycle of the application in order to prevent excessive soot accumulation and plugging of the diesel particulate filter. The ECM will set this fault if it detects that the soot level has exceeded the normal desoot trigger threshold by a sufficient amount to indicate that the driver intervention is required. There is not a MIL lamp associated with this fault code, though the driver will be notified via the EVIC message.
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 2007.5 Dodge Ram 3500 HD,QC, 6.7L Cummins, 6speed Auto, 4X4, Bighorn Edition. Click for installs: Carr Steps PML Diff Cover Edge Juice with Attitude Volant Intake Hankook ATM RF10 
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