6.7L Cummins Forum

Squid · #1 (**permalink**) 12-24-2007, 07:16 PM

6.7L DIESEL

EXHAUST SYSTEM - 6.7L DIESEL- P/U

1 - DIESEL OXIDATION CATALYST (DOC)
5 - MUFFLER
2 - NOx ABSORBER CATALYST (NAC)
6 - TAILPIPE
3 - DIESEL PARTICULATE FILTER (DPF)
7 - INSULATOR
4 - BAND CLAMP

The diesel engine exhaust system consists of:
· Exhaust Manifold
· Turbocharger
· Exhaust pipe
· Catalytic Converter
· Diesel Oxidation Catalyst (DOC)/Diesel Particulate Filter (DPF) Assembly (Cab Chassis)
· Diesel Oxidation Catalyst (DOC) (P/U)
· NOx Absorber Catalyst (NAC) (P/U)
· Muffler
· Tailpipe

Exhaust gases travel from the engine turbocharger through the front exhaust pipe into the exhaust system Aftertreatment. The Aftertreatment consists of the Diesel Oxidation Catalyst (DOC) and a Diesel Particulate Filter. The DOC treats the exhaust gas by converting harmful carbon monoxide, unburned hydrocarbons and other compounds into water, carbon dioxide and heat.
The partially treated exhaust gases from the DOC flow into the catalyzed Diesel Particulate Filter (DPF) which traps and accumulates particulate matter (soot) and further treats the exhaust gases to reduce harmful compounds. The trapped particulate molecules will be periodically removed from the DPF through a thermal regeneration process initiated by the engine's electronic controls.
The exhaust gases are then forced through the muffler for noise control. From the muffler the treated exhaust gases flow through the tail pipe and out into the ambient atmosphere.

WARNING: The normal operating temperature of the exhaust system is very high. Therefore, never work around or attempt to service any part of the exhaust system until it is cooled. Special care should be taken when working near the catalytic converter or DOC/DPF. The temperature of these units rises to a high level after a short period of engine operation time.

Aftertreatment
The P/U Aftertreatment consists of a Closed Coupled Catalyst (CCC) The CCC is a Diesel Oxidation Catalyst (DOC) that is mounted very close to the turbocharger exhaust outlet. It is a metallic flow through substrate coated with a catalyst washcoat that is essential to the integrated operation of the aftertreatment 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. The ability to create heat is an important part of the system regeneration process.
NOx ADSORBER CATALYST (NAC): The NAC is located downstream of the CCC. Using the heat and exhaust constituents coming from the CCC, the NAC traps various oxides of nitrogen, and then converts those into Carbon Dioxide, Nitrogen (N2) and water via a regeneration process controlled by the engine's electronic control module (ECM). The NAC also plays a role in reducing non-methane hydrocarbons (NMHC) from the exhaust gas.
DIESEL PARTICULATE FILTER (DPF): The diesel particulate filter (DPF) is a wall-pass ceramic filter substrate coated with a catalyst washcoat. It is located just downstream of the NAC. Exhaust gases flow from the NAC into the catalyzed diesel particulate filter (DPF) which traps and accumulates particulate matter, and further treats the exhaust gases to reduce any remaining unburned hydrocarbons and other harmful compounds. The trapped particulate matter will be periodically removed from the DPF via a regeneration process controlled by the engine’s electronic control module (ECM).

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