LML Duramax Emissions
LML Duramax Emissions Information & Specifications
LML Duramax emissions had to be less than the LMM to comply with stricter EPA emissions standards. To accomplish this, GM introduced the SCR (Selective Catalyst Reduction) system to work alongside with the existing DPF, DOC, and EGR systems. The LML Duramax emits significantly less emissions than the outgoing LMM. This is mostly attributed to the SCR/DEF system. Numerous improvements to the existing emissions components help as well however. Many of these emissions devices are problematic in LML model years (2011-2012). We go into more detail about those issues in our “LML Duramax problems” page. Emissions devices are much more reliable in post-2012 trucks. In any case, we wanted to help our readers understand LML Duramax emissions. Here is everything you need to know!
Diesel Particulate Filter (DPF)
Originally implemented in GM’s trucks in the LMM Duramax, the DPF, or Diesel Particulate Filter, is responsible for the collection and removal of soot. How is soot removed? Trucks undergo a process called regeneration in which hot exhaust gases burn the filter’s accumulated soot, thus cleaning the filter. This can occur by two methods. Passive regeneration is the result of naturally occurring high EGTs or exhaust gas temperatures during normal operation. Residual hydrocarbons burn from the filter when exhaust gas temperatures reach a certain level. Active regeneration, however, is the regeneration we most commonly think of. Active regeneration occurs when the Diesel Particulate Filter needs a cleaning. Fuel is injected into the exhaust stream, raising EGTs and burning collected soot.
One major reason LML Duramax emissions are more effective is the revised active regeneration design. The LML utilizes a “9th injector” design. A ninth injector is present on the downpipe that injects fuel into the exhaust to raise EGTs. These higher temperatures then proceed to burn accumulated soot within the DPF. This design resolves the cylinder washing concern from the LMM Duramax. The new active regeneration process is greatly improved, but the DPF still contributes to lower fuel economy.
Exhaust Gas Recirculation (EGR)
Nitrogen oxides form naturally during the combustion process. Higher exhaust temperatures, however, greatly increase the amount of nitrogen oxides formed. Because of this, manufacturers introduced the EGR system. The EGR system removes a small portion of exhaust gases from the exhaust manifold and re-routes the gases into the intake. This lowers combustion temperature and effectively reduces the amount of NOx emitted from the tailpipe.
Diesel Oxidation Catalyst (DOC)
The Diesel Oxidation catalyst performs a similar role to the catalytic converter. By creating an oxidization reaction, the DOC converts carbon monoxide and hydrocarbons into carbon dioxide and water. The DOC helps reduce diesel exhaust fluid consumption, therefore making the SCR process more efficient.
Selective Catalytic Reduction (SCR)
GM added Selective Catalytic Reduction to the LML Duramax to help further reduce emissions. The SCR process begins with the injection of diesel exhaust fluid into the exhaust stream. Diesel exhaust fluid is made up of 1/3 Urea and 2/3 deionized water. The heat from the exhaust gas transforms the DEF into ammonia and carbon dioxide. When these gases enter the SCR catalyst, a reduction reaction occurs which converts harmful Nitrogen oxides to nitrogen and water. LML Duramax emissions successfully reduce NOx emissions by 63% over the LMM by using the SCR system. The usage of DEF has actually helped increase fuel economy as well.
More LML Duramax Information
For more information about the LML Duramax you can visit our LML Duramax specifications page. We break down all the nitty-gritty details about the LML Duramax, including DEF tank capacity and more!