Over the years, as emission regulations have gotten stricter, diesel engine manufacturers have had to adapt. In 2007, all the major players introduced engine changes to meet those new regulations making it the most significant year for emissions compliance updates to date. GM was no exception. The Duramax LMM was built to meet the new emission standards mandated for particulate matter (PM) and nitrous oxide (NOx) limits. +Read more
Where Cummins and Powerstroke came out with completely new engines, Duramax chose to modify the 6.6L Duramax LBZ with a complex exhaust after-treatment system in order to meet the new emissions standards. With this change, since it was technically a new engine, they also needed to change the engine code. Thus, the LMM Duramax was born.
Interestingly enough, the Duramax LMM, despite having more stringent emission standards, was able to increase its power output and remain a step or two ahead of Ford and Dodge with 365 horsepower and 660 lb-ft of torque. New emission equipment introduced with the launch of the LMM included exhaust gas circulation, a diesel particulate filter and a diesel oxidation catalyst.
However, some trouble spots arose with the LMM centered around the new emission standards equipment. The complicated exhaust after-treatment system lead to poor fuel economy, diluted engine oil and reduced the life expectancy of the engine. Cracked pistons were also pretty typical with the LMM due to the pistons being identical to the LBZ but now were subject to the increased power output of the LMM.
Despite these drawbacks, the LMM Duramax does have several benefits compared to the LBZ including cast-aluminum heads and revised fuel injectors which added power and more complete combustion.
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