Duramax Emissions Explained

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Duramax emission systems and the years introduced

• 2001 LB7 - No EGR or Catalytic converter.
• 2002-2004 LB7 - ECM controlled vacuum operated EGR with cooler and Catalytic converter 2002 w/ California emissions.
• 2004.5 -2005 LLY - Larger ECM controlled electric motor actuated EGR with cooler and Catalytic converter.
• 2006-2007 LLY-LBZ - Larger ECM controller and electric motor actuated EGR valve and cooler and Catalytic converter.
• 2007-2010 LMM - Larger EGR cooler than prior years and the addition of the DPF. DPF regeneration is accomplished by late injector timing and injection pulses to raise exhaust gas temperatures in the DPF to burn off collected soot.
• 2011-2016 LML - Additional EGR cooling, EGR valve redesign, EGR cooler bypass valve, and the addition of the SCR and DEF fluid. DPF regeneration is accomplished by the addition of the 9TH fuel injector or indirect injector that reduces oil dilution by injecting fuel directly into the exhaust system.
• 2017-present L5P - A reconfiguring of the EGR and other emissions to help mitigate stricter emissions standards. The L5P has 4 stages of exhaust treatment:
  • The use of a close coupled DOC (directly attached to the back of the turbo).
  • SCR, Selective Catalyst Reduction.
  • additional DOC, Diesel Oxidation Catalyst.
  • DPF, This used in conjunction with the EGR and DEF.

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Diesel emissions components are used for the mitigation of these byproducts of the diesel combustion process:

• Carbon Monoxide (CO₂) incomplete combustion.
• Hydrocarbons (HC) incomplete combustion.
• Nitrogen Oxides (NOX) High combustion chamber temperatures.
• Particulate Matter (PM) incomplete combustion (soot).

*The use of common rail high pressure fuel injection and precise injection timing has facilitated a reduction in HC, CO and NOX as a result of more efficient combustion.

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Here are the 7 emission components and their role in the reduction of tailpipe emissions:

EGR Valve

Controls the formation of NOx by displacing some oxygen (O₂) and reducing combustion chamber temps by introducing inert gases to the combustion chamber. NOx is formed in the combustion chamber when temps rise above 2500 deg. F.

EGR Cooler

Reduces EGR gas temperature to make the EGR more efficient at lower NOx formation.

EGR Bypass Valve

This is used to help warm the combustion chamber and DOC during cold starts operation.

Diesel Oxidation Catalyst or DOC

The DOC processes the HC and CO into carbon dioxide (CO₂) and water (H₂O) , it doesn’t remove the NOx but oxidizes it to NO₂ for the DPF and SCR function.

Hydrocarbon Injector (indirect injector)

This fuel injector is ECM controlled and injects diesel fuel directly into the exhaust system just in front of the DOC. The addition of diesel fuel to the DOC generates exhaust gas temperatures for the operation of the after treatment system.

Diesel Particulate Filter

The DPF is a porous filter used to trap particulate matter or soot. The filter is up to 90% efficient at removing particulate matter from tailpipe emissions. PM build up will trigger a regeneration event to burn off the collected soot. Exhaust gasses must exceed 1022 deg. F to burn off the collected PM.

Selective Catalyst Reduction SCR

The function of the SCR is to reduce NOX into N₂ nitrogen, CO₂ and H₂O. This is done in conjunction with the injection of DEF into the SCR. DEF or diesel exhaust fluid is made up of UREA and deionized water a carrying agent for ammonia NH₃ the component used in NOX reduction.