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Thread: LML Exhaust Regeneration

  1. #1
    Join Date
    Apr 2001
    Location
    Alvin, TX, USA
    Posts
    192

    Default LML Exhaust Regeneration

    Whenever the exhaust regen occurs on my 2012 3500HD Duramax, I have noticed 2 things. One, idle speed increases about 200 RPM; and two, fuel mileage steadilly decreases for the 20 minutes or so regen occurs. Running empty, fuel mileage will ultimately be reduced 2 to 3 mpg. Will regain perhaps 1 mpg (at best) of that loss before next fillup. Is there any way to reduce that mileage impact?

  2. #2
    Join Date
    Feb 2000
    Location
    Montana
    Posts
    11,382

    Arrow

    As soot builds in the DPF, exhaust restriction increases. The rate at which soot accumulates depends on several factors, with exhaust temperature being one of the bigger factors.

    Those who tow or run at freeway speeds for longer periods see fewer active regenerations. While towing, exhaust temperature could be high enough that the soot is being consumed at nearly the same rate as it builds in the filter.

    Cooler temperatures that occur during the winter months compound the problem - if you can call it that. If you know that you'll be driving around town or locally in cold/cool temperatures, you might be better off driving some other vehicle, if one is available. The only downside to driving a DPF -equipped diesel pickup during such times is a hit to fuel economy because of the active exhaust system regenerations.

  3. #3
    Join Date
    Apr 2001
    Location
    Alvin, TX, USA
    Posts
    192

    Default

    Is there any kind of notice given by the DIC when a regen is occurring? I have not seen one or found one. Just noticed the mileage dropping or idle speed being higher. Am I missing something? Think I read that Ford tells you.

  4. #4
    Join Date
    Nov 2012
    Location
    St. Augustine, Florida
    Posts
    14

    Default

    I don't think it tells you anywhere. The only way I know is the elevated idle and the motor actually sounds a little different during acceleration.

    2012 3500HD Silverado LTZ Duramax 6.6 Dually 4X4 pulling a
    2012 Keystone Avalanche 341TG in the quest of happiness!
    Proud member #980 of The 3500 Dually Club

  5. #5
    Join Date
    Mar 2000
    Location
    Loyal WI US
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    10,792

    Default

    It only tells you if it's PO'd. It nags you to drive if you let it get loaded by excessive idling etc. Essentially if it gets too much soot load it nags you to drive in order to do a proper regen.

    You can often smell at the rear of the truck when it's in regen also.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  6. #6
    Join Date
    Mar 2000
    Location
    Loyal WI US
    Posts
    10,792

    Default

    I've been working on "emissions intact" tuning for the LML and have been having pretty good success so far with MPG, responsiveness, a good bit of power on demand, PLUS I had a pretty decent run between regens during unloaded highway driving.

    Been monitoring the regeneration and need to do some studying as to the triggers as last regen was long on miles, but at a low soot accumulation.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  7. #7
    Join Date
    Apr 2004
    Location
    Bar Nunn, WY
    Posts
    193

    Default

    I think it starts at 700 miles or 44 grams of soot (at least on my LML).

    Jay
    2023 Tahoe 3.0l diesel
    2013 Harley Switchback
    2021 Ram 2500 6.7l (sold)
    2018 Chevy Traverse (sold)
    2021 Silverado 3.0l LM2 (sold)
    2019 GMC Sierra 6.2l (sold)
    2019 Colorado ZR2(sold)
    2017 2500HD CC D/A (sold)
    2015 1500 CC High Country 6.2l (sold)
    2010 Chev 2500HD CC D/A (sold)
    2013 Chev 2500HD CC D/A (sold)
    2006 Chev 3500 CC D/A (sold)
    2005 Harley Ultra Classic (sold)

  8. #8
    Join Date
    Mar 2000
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    Loyal WI US
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    Default

    I believe from what I have been reading is that there is a 700 mile component to this as well as differential pressure/soot load.

    Mine was doing mid 300's but last one was at 700 and only 24g soot load at the time it started. It finished in 34 miles but dropped the DIC MPG very little then started to recover quite quickly.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  9. #9
    Join Date
    Apr 2004
    Location
    Bar Nunn, WY
    Posts
    193

    Default

    My truck regens between 400 and 700 miles on summer fuel. It drops with winter fuel. Here in MN, summer diesel is all B20 which may help with longer times between regens. Winter fuel is B4. The 700 miles bugs me. It a total waste of fuel to go into regen just because I went 700 miles since the last one. I can actually watch the soot load drop on it's own when I'm towing heavy (no need for active regen).

    I would really like to have my truck reprogramed, but can't afford to loose the warranty. I don't need any more power, but it would be nice to get a little better mileage. I may think a little different after the truck get closer to the end of the warranty.

    Jay
    2023 Tahoe 3.0l diesel
    2013 Harley Switchback
    2021 Ram 2500 6.7l (sold)
    2018 Chevy Traverse (sold)
    2021 Silverado 3.0l LM2 (sold)
    2019 GMC Sierra 6.2l (sold)
    2019 Colorado ZR2(sold)
    2017 2500HD CC D/A (sold)
    2015 1500 CC High Country 6.2l (sold)
    2010 Chev 2500HD CC D/A (sold)
    2013 Chev 2500HD CC D/A (sold)
    2006 Chev 3500 CC D/A (sold)
    2005 Harley Ultra Classic (sold)

  10. #10

    Default

    I put 120K miles on my last 2009 LMM, only had it bother me about a regen once that I recall.

    Most of the time they must have happened while towing, and since my average MPG loaded/unloaded hovered in the 12s, it wasn't really noticable.

    The more you tow, I guess the less of an issue the DPF is. I was amazed at how clean the tailpipe remained over time...basically ZERO soot accumulation, indicating that not much makes its way out.
    2011 Chevrolet Tahoe 5.3L daily driver
    • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
    • Total GM diesel miles to date : ~950K

  11. #11
    Join Date
    Mar 2000
    Location
    Loyal WI US
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    10,792

    Default

    What I have observed is that a typical regen cycle yields about 12mpg empty based on the DIC average. The longer the regen, the more your avg MPG will drop.

    As for the tail pipe soot, remember, the big air gap allows lots of air through and it tapers outward so there's not much contact with the walls. Look back inside the main pipe and you'll see some black.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  12. #12
    Join Date
    Apr 2001
    Location
    Alvin, TX, USA
    Posts
    192

    Default Exhaust Regen

    Guys, especially John, my 2012 regens about every 250 miles empty. Some of you get 400 to 700 before regen?

  13. #13
    Join Date
    Mar 2000
    Location
    Loyal WI US
    Posts
    10,792

    Default

    I'm still getting consistent 700 mile regens at about 24 grams soot load. If I had the ability to extend the regen miles through programming I'm sure I could get close to double the miles before the max soot load is reached. While double 24grams is 48, the base soot after regen always pops back up to several grams minimum shortly after the regen cycle is complete.

    I had an email conversation with a customer who thought he was getting long regens. He went on a trip and found it to be in the 200-350 range.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  14. #14
    Join Date
    Oct 2000
    Location
    Defiance, MO USA
    Posts
    170

    Default

    I just made a verbal commitment on a 2014 2500HD Duramax. I have been hunting for info on fuel mileage posted on the web. I have high hopes the 2014 will get better MPG than my current 2001 which is around 16mpg. Now I am worried after reading this thread. I seldom haul or pull anything. I bought/am buying a 2500HD diesel because I like the power and hate transmission downshifts on lesser vehicles every time you encounter a slight grade when cruise control is on. Since I won't be working the engine hard I will probably have frequent regens and my MPG will suffer.
    2014 K2500HD Crew Cab LTZ Duramax / Allison 4x4

  15. #15
    Join Date
    Aug 2003
    Location
    Tucson, AZ
    Posts
    109

    Default

    Those of you who can tell when your vehicle is in regen mode, how do you know? The only time I ever knew my '09 needed regen is when it told me I needed to do it. That was because I was driving only around a campground for two weeks. Do you think perhaps the reason I don't know it is because virtually all the time I use the truck, I'm carrying a 4k camper and towing a Jeep Wrangler?
    Bob
    2009 LTZ 3500 D/A ext-cab DRW
    1993 11' 3" Lance cabover camper

  16. #16
    Join Date
    Feb 2014
    Location
    Loveland CO
    Posts
    4

    Default

    Quote Originally Posted by Kennedy View Post
    I believe from what I have been reading is that there is a 700 mile component to this as well as differential pressure/soot load.

    Mine was doing mid 300's but last one was at 700 and only 24g soot load at the time it started. It finished in 34 miles but dropped the DIC MPG very little then started to recover quite quickly.
    How do you find out your soot load, does it say in the DIC?

  17. #17
    Join Date
    Mar 2000
    Location
    Loyal WI US
    Posts
    10,792

    Default

    Soot load is monitored in the scan data.

    I encourage my tuning customers to start with the Edge Insight: http://www.kennedydiesel.com/detail.cfm?ID=673


    The Insight is used to monitor the soot load among other things. It is also a useful coach in that when you see it beginning the regen mode you can drive accordingly. In my case knowing that the regen is coming every 700 miles like clockwork is also helpful. Whenever possible I try to plan to be on the highway when this comes around.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  18. #18
    Join Date
    Oct 2000
    Location
    Defiance, MO USA
    Posts
    170

    Default The picture tells it all

    With about 450 miles on the odometer this was snapped after an hour at 70mph with cruise on. This is what makes me question a good many folks who claim they get 20+mpg. I don't think my new baby would get that going down hill with a tail wind.
    Attached Images Attached Images
    2014 K2500HD Crew Cab LTZ Duramax / Allison 4x4

  19. #19
    Join Date
    Feb 2014
    Location
    Loveland CO
    Posts
    4

    Default

    Quote Originally Posted by Kennedy View Post
    Soot load is monitored in the scan data.

    I encourage my tuning customers to start with the Edge Insight: http://www.kennedydiesel.com/detail.cfm?ID=673


    The Insight is used to monitor the soot load among other things. It is also a useful coach in that when you see it beginning the regen mode you can drive accordingly. In my case knowing that the regen is coming every 700 miles like clockwork is also helpful. Whenever possible I try to plan to be on the highway when this comes around.
    I have a Edge Insight that I had in my old truck, I got it last year, it is version REV 04 with a build date of 05/2011 also has this number as well# H00001700. I can not find the soot load on my devise, if it is not the latest version I believe I can download the newest version to my Insight, is that correct? I just want to learn all about this regen business, also will my motor noise be louder during regen? Today my injectors were real loud at around 2100 RPM to about 2400 then it got quite again. Thank you for your patience this new truck is a hole different animal then the LB7 I have been driving for 12 years. I am very interested in buying your tune when your ready to release it.

  20. #20
    Join Date
    Mar 2000
    Location
    Loyal WI US
    Posts
    10,792

    Default

    You'll want to go to Edge site and download their Fusion program to update your unit.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

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