TheDieselPage.com Forums
 
The Diesel Page Forums

2019 - TDP's 23rd Anniversary
What's New | Feature Articles | Product Reviews | Member's Area | Free Forum Registration
Duramax 6600 Diesel Page | Advertiser's Section | Classified Ads | The Diesel Page - Publications


Go Back   TheDieselPage.com Forums > 2001-2019 Chevrolet & GMC 2500HD/3500 Light Trucks > Duramax 6600
Register FAQ Members List Photo Album Mark Forums Read

Duramax 6600 Welcome to the Internet's first Duramax 6600 diesel discussion forum for the LB7, LLY, LBZ, LMM, LML, LGH & L5P RPO code engines. Tips on performance, fuel economy, troubleshooting and more.

Reply
 
Thread Tools Display Modes
  #1  
Old 04-11-2007, 10:20 PM
More Power's Avatar
More Power More Power is offline
Administrator
 
Join Date: Feb 2000
Location: Big Sky Country
Posts: 10,479
Arrow LMM Fuel Economy

I visited the local GMC dealer today and discussed the first LMM 2500HD crew cab they sold a week or so ago. I had hoped to shoot some photos of that one, but missed it. However, I did get some shots today of an LMM equipped 3500HD chassis cab...

The owner of the LMM 2500 reported that his first tank of fuel produced 17 mpg while running at Interstate speed across Montana. This owner has owned a number of Duramax powered trucks prior to this one, his LB7's would produce close to 20 on the same trip, and his last Duramax (a 2005 LLY) struggled to produce 15. So, he's happy with the LMM... so far...

Jim
Reply With Quote
  #2  
Old 04-12-2007, 04:42 PM
D_R_C's Avatar
D_R_C D_R_C is offline
Enthusiast
 
Join Date: Apr 2007
Posts: 101
Default

Quote:
Originally Posted by More Power
I visited the local GMC dealer today and discussed the first LMM 2500HD crew cab they sold a week or so ago. I had hoped to shoot some photos of that one, but missed it. However, I did get some shots today of an LMM equipped 3500HD chassis cab...

The owner of the LMM 2500 reported that his first tank of fuel produced 17 mpg while running at Interstate speed across Montana. This owner has owned a number of Duramax powered trucks prior to this one, his LB7's would produce close to 20 on the same trip, and his last Duramax (a 2005 LLY) struggled to produce 15. So, he's happy with the LMM... so far...

Jim
Keep us/me posted I ordered the new body sierra LMM 3500 SRW SLT 4X4 long bed and hope to get it by the end of May.
Anything has to be better than the 6.0 disaster I had.
I know it is early reports but "Thanks for the info".
Reply With Quote
  #3  
Old 04-13-2007, 11:58 AM
More Power's Avatar
More Power More Power is offline
Administrator
 
Join Date: Feb 2000
Location: Big Sky Country
Posts: 10,479
Arrow

Here's a shot of the 2007 LMM equipped chassis cab.



GVW is reported as being 12K. This one is equipped with dual fuel tanks and 4WD. The exhaust system is equipped with a DOC (Diesel Oxidation Converter) and DPF (Diesel Particulate Filter), but no muffler. Also, the air mixing exhaust tip is a downturn tip ahead of the rear axle.



The engine looks very much like the outgoing LBZ, except there is now a throttle valve in the intake plenum, upstream of the intake air heater.

Jim
Reply With Quote
  #4  
Old 04-14-2007, 04:35 AM
DieselMonk DieselMonk is offline
Enthusiast
 
Join Date: Jan 2007
Posts: 115
Default

[QUOTE=The engine looks very much like the outgoing LBZ, except there is now a throttle valve in the intake plenum, upstream of the intake air heater.

Jim[/QUOTE]

I am trying to compare it to my late production LBZ (12/06). Could you make either a better picture or circle that "throttle valve" please? Ran in the garage this morning and took couple of pictures of my engine compartment to compare it to your pic.
The only thing that is missing on mine is that silver shielded cable thats fastened along the firewall behind the plastic 6.6L cover.
__________________
07 Chevrolet Classic, CC, regular box, Duramax Diesel, Magnaflow dual exhaust and Superchips tuned.
Reply With Quote
  #5  
Old 04-14-2007, 09:10 PM
More Power's Avatar
More Power More Power is offline
Administrator
 
Join Date: Feb 2000
Location: Big Sky Country
Posts: 10,479
Default

GM calls it an "Air Intake Valve", which is controlled by the ECM. The valve is activated during DOC/DPF regeneration, EGR operation and "rich idle".


Jim
Reply With Quote
  #6  
Old 04-17-2007, 10:00 PM
Duramaster's Avatar
Duramaster Duramaster is offline
GMC World Class Technician
 
Join Date: Mar 2007
Location: Pacific Northwest
Posts: 735
Default

What did you think of that downturn pipe just ahead of the rear differential?

The C-4500/ C-5500 trucks are the same way. Looks kind of scary!
Reply With Quote
  #7  
Old 10-21-2007, 07:58 PM
RaiderCoach RaiderCoach is offline
Newbie
 
Join Date: Oct 2007
Posts: 6
Unhappy mpg & programmer - not happy with LMM

I purchased an LMM crew cab 4wd in May. The fuel economy was never better than 16 mpg hwy and 13 hwy city. I lifted the truck and put 33" tires on it and hoped that it was a break in issue. My previous truck, an 03 duramax, would average 15 mpg city and up to 22 mpg hwy empty and 14 - 17 mpg hwy towing, varied depending on weight of load from 7000 to 12,000 lbs. I had an edge juice programmer on that truck. I recently put a Bully Dog Power Pup on this truck, really hoping for some mpg results. Being able to correct the speedo was nice, the truck didn't really need that much more power. No matter what the setting that I have the Bully Dog set to, I am averaging right at 13 mpg in town and 17 hwy. I have a very light right foot, so unless milage would increase with a heavy foot, I am probably at about where I'm going to be. Currently the truck has 9400 miles on it. I really miss my 03 and wish I had stayed with it.
Reply With Quote
  #8  
Old 10-22-2007, 06:53 PM
craigth craigth is offline
Newbie
 
Join Date: Oct 2007
Posts: 7
Default Does GM know about the LMM MPG issue?

I lifted my truck with a ProComp 6" and 34" tires in Sept '07. You can see pictures in the TDP Photo Album page.

Interesting that you were able to adjust the speedo as the local GMC dealer said it couldn't be one with Allison transmissions! They also said that I couldn't have the tire pressure sensor set lower than 62PSI. However, a friend of mine with an '08 LMM 3500 said his dealership awas able to lower it in the 50PSI range. Not real happy with the knowledge and willingness to service non-standard features at the dealership.

Was the tuner worth it for performance? Did it make any noticable difference? Why did you select the Bully Dog tuner over another brand?

I wonder if GM knows about the LMM MPG issue?! I also wonder if this forum and the members of the TDP could use their numbers to communicate the issue and see if GM can tell us why and/or address the problem with some modifications.

It's really sad that in this time of high gas prices and diesel technology promoted as high mileage GM can't at least maintain or better yet increase the MPG of their LMM trucks. Most vehicles from year to year increase their MPG not decrease.

Maybe GM will get the wake up call they need when Toyota producesa 2500/3500 series of trucks with their own diesel! I'm sure their MPG will be high and more than likely the truck features and quality will be superior!
Reply With Quote
  #9  
Old 10-22-2007, 08:56 PM
RaiderCoach RaiderCoach is offline
Newbie
 
Join Date: Oct 2007
Posts: 6
Default LMM and Tuner

I went with the Bully Dog because the sales manager at the dealership that I use recommended it. My previous tuner, in my 03, was an Edge Juice. It worked really well, but I did have some stalling problems so I decided to try this one. The Bully Dog does allow you to tune the speedo to your tire size, although I have not checked it to make sure that it really did anything. There is definetely a power difference, although for street driving without a load, I don't really feel that there's a need for the increase. I netted about 1 mpg increase, far below the 3 mpg increase that I realized with my 03 and the Edge product. I would not recommend spending the $500 for that small of an increase. I'll be taking my truck in for it's 10k oil change soon and will talk to the service manager about the milage issue, although I know the answer already that I'll get. It will be "We're not aware of anything wrong"? Always the same answer, until GM sends out a bulletin in about 6 months...
Reply With Quote
  #10  
Old 11-22-2007, 06:51 AM
Dakster Dakster is offline
Enthusiast
 
Join Date: Jan 2007
Posts: 299
Default

Here's what I have noticed. Each boards mileage claims vary as much (or more) than the mileage I actually get with my own truck. My normal everyday driving I get lousy mileage. Although, I take a lot of short trips and even my longer ones as on So. Florida parking lots (highways). The heat and being at or under sea level doesn't help either. (Doesn't make sense to me, but I get MUCH better fuel economy once I hit the rolling hills of GA and it stays that way until I get back home from Connecticut or in last years case Tennessee)

Obviously the LMM gets worse mileage than its predecessors, and from what I have expereinced and read it has a lot more power, and a restrictive exhaust too. The best case people seem to say about 1 mpg less and others up to 5-6 mpg less. My LMM gets better MPG than my gas 2007 6.0 Suburban (4x4) and 2005 Denali XL (AWD) and about the same as my 2005 Ford F250, 6.0 DIESEL, 4x4, CC, SB. Which is around 12 in local driving in town and 14-15 on highwy drives, but I drive fast 75-80. And yes, I wish I got better MPG's, but don't we all?
__________________
2007 Silverado, 3500HD, 4X4, CC, Long Bed, SRW, LMM Diesel, Navi, DVD, Roll-N-Lock Cover, ICI Running Boards, CoastalEtech GM Lockpick for DVD/Nav changes in Motion, Back-up Camera...

2006.5 VW Jetta Special Edition TDI - Blue Graphite - European Spec VW Fact. Nav Radio.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 04:20 AM.


Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright 1996-2019 by TheDieselPage.com - All Rights Reserved