6.6L Duramax LMM

Duramax LMM Specs & Info

Like its competitors, a diesel particulate filter (DPF) system had to be adopted by the Duramax in order to meet Federal emissions regulations in the U.S. The result was the LMM, nearly identical to the LBZ save for programming changes necessary to integrate the DPF and its required regeneration system. GM reports that this engine and its adopted emissions technologies were able to cut particulate emissions by up to 90 percent over previous generations. The backlash of the DPF system was a severe reduction in fuel economy resulting from periodic regeneration cycles required to clean the particulate filter and prevent clogging.

LMM, an Emissions Friendly Duramax Diesel

The LMM made its debut midway into the 2007 model year, phasing out the previous generation LBZ. The new diesel particulate system required "active regeneration" in order to periodically clean the DPF by means of literally burning the collected material. The LMM used a less favorable late and post injection technique in order to introduce raw diesel fuel into the diesel particulate filter, which is necessary to inhibit the high temperatures necessary for regeneration to occur. The late and post injection technique, as opposed to the "9th injector" technique, poses the threat of cylinder washing and fuel dilution as a result of raw diesel fuel passing through the cylinder on its journey to the exhaust system. The "9th injector" system, which would be adopted by the current LML Duramax, is considered favorable and eliminated these concerns. The typical response to abnormally high fuel dilution is to make sure that maintenance is performed regularly per the owners manual. The threat has yet to surface as a serious cause for concern, at least in the short run, despite criticism.

The primary highlight of the LMM is that it met strict EPA mandated emissions requirements for the 2007 model year. A manual transmission was never offered with the LMM, and therefore every engine on the road is backed by the Allison 1000 six speed automatic. Though manual transmissions have never been particularly popular with Duramax buyers, there are those that wish the stick shift option would not have disappeared. Ford would continue to offer a six speed manual through the 2009 model year, and Ram Trucks still offers a manual transmission - although at a serious reduction in torque output.

6.6L Duramax LMM Specs

Engine:

6.6L Duramax LMM, 90 degree V8 diesel

Years Produced:

2007.5 - 2010

VIN Code:

6 (8th digit of VIN)

Assembly Site:

DMAX engine plant, Moraine, Ohio

Displacement:

403 cubic inches, 6.6 liters

Head/Block Material:

Aluminum cylinder heads, cast iron engine block

Compression Ratio:

16.8 : 1

Firing Order:

1-2-7-8-4-5-6-3

Duramax diesel cylinder numbers

Bore:

4.055" (103 mm)

Stroke:

3.897" (99 mm)

Aspiration:

Turbocharged & intercooled - Garrett variable vane turbocharger (VVT), air-to-air intercooler

Injection:

26,000 psi Bosch high pressure common rail with CP3 injection pump

Valvetrain:

OHV (overhead valve), 4 valves per cylinder

Oil Capacity:

10 quarts with filter

Engine Weight:

Approximately 835 lbs

Max Engine Speed:

3,450 rpm

Emissions Equipment:

• Diesel Particulate filter (DPF); minimizes particulate emissions
• Exhaust gas recirculation (EGR); reduces NOx emissions
• Diesel oxidation catalyst (DOC); converts carbon monoxide into CO2 & water

Peak Horsepower:

365 hp @ 3,100 rpm

Peak Torque:

660 lb-ft @ 1,800 rpm

Engine Dimensions:

Length

Width

Height

Approx 30"

Approx 30"

Approx 32"

The LMM offered a slight increase in horsepower (+5) and torque (+10) over the LBZ. However, in GMC and Chevrolet class 4/5 trucks (4500/5500 models) the Duramax LMM was available in either a 300 hp/520 lb-ft or 330 hp/620 lb-ft version. The 2500/3500 Van variation of the engine made 250 hp/460 lb-ft of torque and mated to GM's Hydra-Matic 4L85-E four speed automatic transmission instead of the Allison 1000. Detuning is common in commercial vehicles. 2010 was the last model year that the LMM was available, as it was replaced by the more powerful, more efficient LML for the 2011 model year.