GM Truck Club
THE PREMIER CHEVY TRUCK & SUV FORUM
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER

I disabled AFM as an experiment.

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by stchman, Aug 26, 2013.

  1. stchman

    stchman New Member

    Joined:
    Oct 31, 2012
    Messages:
    1,035
    Likes Received:
    1
    I used my Hypertech to disable AFM on my truck as an experiment. SO many folks are constantly talking about oil consumption, AFM makes for WORSE MPGs, etc., that I thought I would give it a try.

    With AFM I get between 17.8-18.3 MPG Monday through Friday back and forth to work.

    I disabled AFM last night and topped off the tank this morning for the drive.

    I got 20.1 MPG driving to work, which is surprisingly slightly better than what I get with AFM on. Now I know weather, fuel blends, etc., have an impact on fuel economy as well, my driving back and forth to work at least takes the terrain out of the equation.

    I will keep the forum posted.

    At the very least, I don't have to hear the AFM turn on and off and hear it on my exhaust.
    #1
  2. ChevyBoy2009

    ChevyBoy2009 New Member

    Joined:
    Jan 30, 2010
    Messages:
    734
    Likes Received:
    2
    So were we right?
    #2
  3. stchman

    stchman New Member

    Joined:
    Oct 31, 2012
    Messages:
    1,035
    Likes Received:
    1
    I'm not going to declare anything after only 25 miles. So far it looks promising.
    #3
  4. Sierraowner5.3

    Sierraowner5.3 New Member

    Joined:
    Apr 2, 2011
    Messages:
    1,950
    Likes Received:
    4
    something to bear in mind is the fact that the ECM relearns things as you drive, so as you get more miles on it should only get better.

    at least for me, the sweet spot if running 60-65 with the cruise on. flat ground the truck returns 23 on the instant econ display, and lots of interstate driving seems to support that.

    Alex
    #4
  5. stchman

    stchman New Member

    Joined:
    Oct 31, 2012
    Messages:
    1,035
    Likes Received:
    1
    The absolute best I ever got on my route to work for the week was 18.8MPG. Not bad for a heavy truck, but if it can do better with disabling AFM, then I'll do it.
    #5
  6. ChevyBoy2009

    ChevyBoy2009 New Member

    Joined:
    Jan 30, 2010
    Messages:
    734
    Likes Received:
    2
    I cant wait to get my Diablo and see what kind of numbers my truck will get :glasses:
    #6
  7. ChevyFan

    ChevyFan Administrator Staff Member

    Joined:
    Dec 1, 2004
    Messages:
    5,002
    Likes Received:
    13
    You should chart it. Do a daily log and include the total miles, the MPG shown, weather conditions, etc.
    #7
  8. McClintoc

    McClintoc Super Moderator

    Joined:
    Aug 18, 2012
    Messages:
    1,573
    Likes Received:
    2
    For the most accurate results, go through several whole tanks with AFM off and then get back to us. Good luck with the experiment!
    #8
  9. mfleetwood

    mfleetwood Moderator

    Joined:
    Jul 6, 2010
    Messages:
    7,213
    Likes Received:
    11
    Good thread topic...thanks for starting it!
    #9
  10. stchman

    stchman New Member

    Joined:
    Oct 31, 2012
    Messages:
    1,035
    Likes Received:
    1
    Update, day 2.

    I arrived at work with the DIC reporting AVG MPG of 19.1. I will report back tomorrow.
    #10
  11. GuyGene

    GuyGene New Member

    Joined:
    May 23, 2013
    Messages:
    38
    Likes Received:
    0
    Sounds good. I've read good things about that Range thingamajig on other forums. It's not a tune, but just cuts AFM mess off.
    #11
  12. bazar01

    bazar01 New Member

    Joined:
    Feb 20, 2012
    Messages:
    291
    Likes Received:
    1
    On my 2011, I get 20mpg on the highway on actual mileage and gas consumption based on full tank going 70 mph.
    City, I just put it on M5 and get 18mpg going from 35-45 mph speed.

    You think the Range programmer will give me additional benefit on mpg?
    #12
  13. phoebeisis

    phoebeisis New Member

    Joined:
    Jun 14, 2006
    Messages:
    1,613
    Likes Received:
    9
    You have no oil consumption problem-right?
    Anyone disable it who has the oil consumption problem?

    Why would it get better mpg with the AFM disabled?
    #13
  14. bazar01

    bazar01 New Member

    Joined:
    Feb 20, 2012
    Messages:
    291
    Likes Received:
    1
    I don't have oil consumption or oil burning issues at all. I change my oil every 7500 miles and still on top mark.
    My mpg seems right on line as advertized. For me I don't see any benefit to disable it unless the 4-cyl mode puts some strain on the engine or causes uneven wear when in 4-cyl mode. Time will tell.
    #14
  15. RayVoy

    RayVoy Active Member

    Joined:
    Apr 18, 2012
    Messages:
    2,122
    Likes Received:
    5
    I just returned from a trip of 1,000 miles, did some experimenting.

    I found (and this is using the DIC, resetting for each test) that if I drove at 40 mph on a 2 lane, I averaged 24.6 mpg (about 100 miles). If I increased to 55 mph, I averaged 20.2 mpg (again, about 100 miles). Interstate driving at 70 -75 mph, I averaged 18.2 mph. AFM was on.

    This was in Maine, a lot of hills.
    #15
  16. ChevyBoy2009

    ChevyBoy2009 New Member

    Joined:
    Jan 30, 2010
    Messages:
    734
    Likes Received:
    2
    Alot of things come to mind and thats why im going to disable it...

    1.Oil consumption issue(rather have my oil in my motor and not in my intake/anywhere else)
    2.Crappy exhaust sound when AFM is on(sounds like a 4 cylinder on steriods with it on)
    3.Better MPG(suppose to get better with it off)
    4.Trucks have 8 cylinders-rather use them all(if you want better MPG-GET A PRIUS!)
    5.Who knows what stress AFM causes to the motor(heat issues,carbon build-up,etc)

    So im going to delete it and see how it goes once my tuner arrives...:great:
    #16
  17. phoebeisis

    phoebeisis New Member

    Joined:
    Jun 14, 2006
    Messages:
    1,613
    Likes Received:
    9
    Chevyboy
    Yeah I buy all that-except the MPG.
    GM engineers too clever to do the AFM for nothing-

    Hey-I do have a 2006 PRIUS-+ a 1998 Suburban-perfect combination really.
    The suburban was just supposed to be a hurricane evacuation vehicle (1,2 tall dogs 4 cats )-new orleans suburb-didn't expect long trip reliability from 195,000 mile vehicle-I wanted get me 100 miles N reliability.
    But it became obvious it was very reliable-with 20 mpg hy mpg.Yeah pleasant surprise.

    the 96-99 Suburbans get 20 mpg hy-and are dirt cheap-$3000 or less
    very reliable drivetrains easy to DIY repair replace parts
    Maybe the last 5.7s were slightly more reliable than the 5.3s-
    but the 5.3s rarely actually break-leave folks stranded.A qt per 500 miles would be annoying-but it wouldn't really inconvenience me-piss me off if I had spent $30,000-
    I expect GM probably has solved the problem on current models-and offers retro fits that work-but they probably try the cheaper retro fits 1st-SOP for car corps.

    If I had a 2007 2008 that had the problem-was out of warranty-I would do the AFM delete-worth a shot.

    The AFM-doesn't really kick in in city driving, right? It is mainly used in low load hy-maybe under 65mph level hy-no head wind?
    Yeah when does AFM kick in? Careful driving-you won't lose much mpg wise.
    #17
  18. bazar01

    bazar01 New Member

    Joined:
    Feb 20, 2012
    Messages:
    291
    Likes Received:
    1
    NO.

    On my 2011, on "D" or M6, when you are going 35-45 mph, AFM kicks in and out and very annoying. So I just put it on M5 and it stays on V8.

    But when going >65mph, you won't even notice when the AFM kicks in and out on "D" or M6.
    #18
  19. phoebeisis

    phoebeisis New Member

    Joined:
    Jun 14, 2006
    Messages:
    1,613
    Likes Received:
    9
    So it kicks in at under 40 mph??

    What is the annoying aspect-the sudden "ricer" sound- or does it give a rough shift feel-little shudder etc?
    I could see how changing from a nice low V-8 grumble-to a 4 cylinder sound-would take some getting used to
    "what happened to my motor"
    #19
  20. bazar01

    bazar01 New Member

    Joined:
    Feb 20, 2012
    Messages:
    291
    Likes Received:
    1
    I really do not care about the exhaust note. It is when it changes from V4 to V8 when you feel the rpm jumps up because of the increased torque of the V8 it could be causing the torque converter to slip a little. Or maybe the TC goes out of lock up mode and the rpm jumps up. Sometimes, the tranny gets hanged up on a certain gear and it does not know here it is at and you can feel the jolt when it shifts. So I just put it on M5 gear and it stays on V8 mode on city driving with a lot of stop and go and slow speeds.
    #20

Share This Page