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I disabled AFM as an experiment.

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

  1. ChevyBoy2009

    ChevyBoy2009 Rockstar 4 Years 500 Posts

    It seems to me every time you let off the throttle it will switch to V4 mode...it gets annoying!...then you get a alittle hesitation if you need to get back into V8 mode while in V4 mode...I also hear that you will gain better throttle response when you have it disabled...it turns on alot during city driving(More than you would expect)
  2. ChevyFan

    ChevyFan Administrator Staff Member 5+ Years 5000 Posts

    Just to be fair to everyone in this thread. GM's chief engineer told me that they acknowleged there were problems with the AFM that they had fixed. I assume they were talking about excessive oil consumption, but who knows? This could be an example of engineering that doesn't apply to everyone all of the time. I'm not going to say yes, not going to say no either. Do a proper and unbiased test and let's see what happens.
  3. ChevyBoy2009

    ChevyBoy2009 Rockstar 4 Years 500 Posts

    I will chart it out when i receive my tuner in the mail...I had a "fix" done about 2-3 weeks ago...i used a quart to 1 1/2 quarts in 962 miles!...i received a carbon cleaning and a updated valve cover and oil topped off...seemed to help(havent HAD to check the oil since then):rofl:
  4. stchman

    stchman Active Member 1 Year 1000 Posts

    Day 3:

    I am so far getting 18.7MPG which is on par with having AFM enabled.

    As for [MENTION=32920]ChevyBoy2009[/MENTION] with the exhaust thing, I have louder muffler on my truck and I can indeed hear when the engine switches from 8 to 4 cylinder(IMO it is not an annoying as people make it out to be). The V4 is actually a deeper tone than the V8 mode. As far as better throttle response with AFM disabled, that is just not true, the throttle response is identical. People that tell you throttle response improves with AFM disabled are obviously under a placebo effect. The switch from 4 back to 8 is pretty much instantaneous, so the only ways one knows about V8 to V4 is aftermarket exhaust and/or the DIC.

    My 2013(so far) and my old 2008 did not suffer from oil consumption. With that being said, they used a little bit of oil (~1qt every 5-6K), but ALL engines will use a little bit.

    I am just doing this as an experiment. IMO, the AFM switches on and off WAY too often to be of a better benefit, I belive that if GM is going to do the AFM thing, then leave it in 4 cylinder mode for a lot longer.
  5. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    Great info
    Chevy- I'm a little unclear-you used 1 1/2 qts in 962 miles,so THEN you had the fix done
    and now it seems like you are using less?? That it??
    Before you get and install the tuner-you'll measure post fix oil consumption?

    A guy from another forum-a mpg forum-is getting his hands on a 2014 5.3 16/23 mpg 355 hp
    He will have it 2-3 days for testing.He did a short drive already-he says it is seamless-going back and forth 4 cylinder to 8 cylinder.
    The 4.3 is no longer the "I can't afford the 5.3" choice-it is 285 hp 18/24 mpg-pretty spectacular mpg and plenty of power.
    I'll pass on his testing of the 2014 5.3 -mpg at a steady 60 mph level highway.It should beat the 3.5 twin turbo Ford in respect to hy mpg-simpler too-twin turbo-kinda complicated .
  6. stchman

    stchman Active Member 1 Year 1000 Posts

    I personally think the transition form V8-V4-V8 on the 2008-2013 5.3L engines is seamless as well.

    The new 4.3L in the 2014 truck from what I understand will be the standard engine in the regular cab and the new extended cab. It looks like it will replace the old 4.8L V8 engine.
  7. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    Sure-the 4.3 won't be the poor relation anymore.
    Before it was strictly the engine you bought if you couldn't afford the V-8
    It didn't beat the 5.3 in FE or anything else
    Now the 4.3 will get spectacular-for a 1/2 ton- FE- beating the Ford and being just one HY mpg down vs the 8 speed Dodge
    It will be a base engine you might actually choose.
    And $$ is $$- it will be in lower trim levels meaning real life it might be $3000 or more less than the 5.3-REAL $$.
    I never would have guessed a 355 hp 5.3 would be rated 16/23-
    it will get city mpg ,about as good as the HY mpg of my 98 Suburban 12/17 EPA
  8. ChevyBoy2009

    ChevyBoy2009 Rockstar 4 Years 500 Posts

    Yes i used 1 1/2 quarts in 962 miles!...then i had the "fix" done and i havent checked the oil yet(they topped it off)-i will tonight. Ive only got about 300-400 miles since then.

    - - - Updated - - -

    Yes i agree the transition from V8-V4-V8 is seamless as well. But I have a cat-back dual exhaust with a glass pack and its pretty noticeable (sound) transition with that set-up(BTW that exhaust sounds amazing)
  9. stchman

    stchman Active Member 1 Year 1000 Posts

    My exhaust is probably not as loud as your exhaust is, but the transition from V8 to V4 was audible, but not that irritating as I am at highway speeds and when I am using my cruise control at 65MPH. I'm only twisting 1600RPMs at 65MPH and my exhaust note is not very noticeable at those speeds.

    I need to make a video of my exhaust note and upload it to YouTube.
  10. ChevyBoy2009

    ChevyBoy2009 Rockstar 4 Years 500 Posts

    At 65 mph i can hear the transition...i love the exhaust when im pulling my 30ft camper also...sounds great!...it doesnt transition as often pulling the camper tho,other than when your going down a hill and then go into V4 then have to go straight up another hill,that transition sucks!...to be honest when im pulling my camper which weights roughly 5,500 lbs at 70 mph on interstate im running around 1,600 to 1,800 rpm...i love that 6th gear!

    - - - Updated - - -

    I like the idea...but do you think it will be very profitable/popular?...I for one would go to the bigger dmax than the smaller displacement one

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