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Home > Inside the 2011 LML Duramax

Inside the 2011 LML Duramax


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AUTOMOTIVE MANUFACTURING HISTORY INCLUDES TWO burtal horsepower wars. The first involved gasoline engines and started when the GI's rerurned from WWII. It ended with the 1973 oil crisis. This oil embargo gave birth to the next slow-starting and fierce-ended fued, which we are all veterans of - the diesel horsepower wars. Notice how power levels have recently leveled off? It's because in 2010, manufactures need to address what's coming out the tailpipe just as much as they have to worry about what number the engine makes. Since we're optimistic and believe the past is a guide, we preict we'll see the emission restrictions turn into a catalyst for better performing diesel engines. Fortunately for us, a world without problems is a very boring place for engineers.

The 2011 diesel pickups built by GM will use the same basic 6.6L engine GM has been using for the last decade. This signifies the original Duramax engine's design was a good foundation - one the engineers didn't need to totally change as we predicted with the 6.9L UMAX ("Detroit Spy Report, April '07). Still, stricter future emissions requirements are putting more pressure on the industry to improve the cleanliness of diesel exhaust without giving up power. The rest of this article highlights the new features on the 2011 Duramax trucks that enable squeaky-clean diesel. Only the future knows for sure whether the new emissions pressure will crush the diesel market into a cube - or a diamond.
2011 Duramax LML
  • Coming down the pipe for the 2011 Silverado and Sierra should be larger-diameter brakes. We expect 13- to 14-inch rotors
  • The torsion bar front suspension has been retained but features more load capacity
  • 1480 U-joints will be used to handle increased cargo and towing capacities
  • The AAM 11 1/2-inch ring gear rear axle will be carried over
  • The body and interior stayed the same, but the chassis has been redesigned in order to increase the gross vehicle weight rating (GVWR)
01-04 LB7 Injectors housed inside valve covers and no EGR, with the exception of California models

04-06 LLY Introduction of Garrett VGT turbo and EGR

06-07 LBZ Revised piston design lowered compression ratio to 16.8:1 from 17.5:1, a stronger block debuted, and a 32-bit ECU was introduced

07-10 LMM Introduction of DPF and exhaust aftertreatment

2011 LML Extra fuel injector placed behind turbo, urea injection, and dual-loop EGR system

2011 LGH Detuned version for 2500 and 3500 vans and will use GM's 6L90 six-speed transmission instead of the Allison 1000
The 2011 Silverado and Sierra will see a larger opening in the front bumper. This modification provides more airflow, and more cooling for the new EGR system and transmission heat exchange. Sources say the new EGR system will have a high and low temperature loop, providing an increased flow rate and a larger window of opportunity for introducing oxygen-depleted exhaust gas gack into the engine. The dead air cools the cylinders and reduces nitrogen oxide (NOx) emissions.
  • The 2011 Duramax traded it slower solenoid injectors for quicker opening and closing piezo units. The common-rail fuel system sprays diesel up to 29,000 psi inside the combustion chamber
  • The 2011 Duramax incorporates urea injection, or as GM calls it, diesel exhaust fluid (DEF). Bells and flashing lights indicate when the DEF needs to be refilled. If the tank goes empty, the truck is sent into limp mode.
  • GM added a ninth injector after the turbo to supply the fuel needed to creat heat that will burn off the emissions built up in the exhaust aftertreatment system. A major benefit of this new system includes not having to deal with oil dilution, which results from biodiesel or regular diesel going past the piston rings and getting into the crankcase. In addition, fuel economy should improve with this more precise setup. Biodiesel compatible fuel lines, an additional heating element in the fuel system, and the latest generation coalescing filter bump the engine's biodiesel rating from B5 to B20.
LML engine
LML engine
This article was written by Jason Thompson with photos courtesy of General Motors.
This article was in Diesel Power magazine March 2010 edition.
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