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Thread: Big off idle stumble, whatt first? IFR? calc.vet? Something else I'm missing?

  1. #11
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by statesman View Post
    It's Aussie humor, and it looks like some people just don't get it.
    you might have to explain it mate...

  2. #12
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Supercharged111 View Post
    It sounds like he's implying that I have a lot of things wrong. If that's the case, why not lay it out instead of making you do it all? If not, I gotbmy panties in a twist over nothing.
    I know he's not having a dig at you, trust me


    remember, we are different (or everyone else is different), we down under view things differently, my wife (born in Anaheim) always reminds me



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  3. #13
    Joe (Moderator) joecar's Avatar
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    Compared to a stock file there appear to be many changes (unless I have the wrong stock file to compare against)...

    did this file start life as a F-car file or as truck file (looks like truck file)...?

  4. #14
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    Quote Originally Posted by joecar View Post
    you might have to explain it mate...
    Everyone knows you've got a busy life, but you still come in here and try to help people. Sometimes it takes a few days before you can look over someone's tune file... "There's a lot to look at in this tune file" is Aussie humor for "you might be waiting a while before Joe gets back to you".

  5. #15
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    Quote Originally Posted by joecar View Post
    Compared to a stock file there appear to be many changes (unless I have the wrong stock file to compare against)...

    did this file start life as a F-car file or as truck file (looks like truck file)...?
    Started as a van I do believe, then converted to COS5, then got a 4L80 added in, and most recently added the 2 bar setup. The only thing preventing me from reverting my IFR and doing a calc.vet is this assumption that I'll adversely affect transient fueling. Since I'm not aware of any transient parameters that I can change, I ASSume the only way is to fudge it in the IFR. Kinda like an older 5.0 Ford I was playing with. Didn't have tuning software, but did have an adjustable FPR and that was the only thing that fixed the off idle stumble in that car (which had better flowing heads and intake and exhaust than stock).

    Quote Originally Posted by statesman View Post
    Everyone knows you've got a busy life, but you still come in here and try to help people. Sometimes it takes a few days before you can look over someone's tune file... "There's a lot to look at in this tune file" is Aussie humor for "you might be waiting a while before Joe gets back to you".
    I know he's a busy guy so I don't want him needlessly looking too much at a tune that I think I know what is wrong with. On the other hand, the only thing I have to lose is gas, but I gain experience. I should probably point out that driveability is good enough for me to DD the thing. When warm I see the wideband peg full lean momentarily but it doesn't seem to stumble and fall on its face so badly then, only when cold. I'm kinda curious if there isn't just a bad handoff from the idle stuff to the VE. Either way that requires VE to be correct. How can I know if my calculated IFR just isn't jiving with the tune?
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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    There's something wrong with your setup. At 3000rpm WOT, you're only getting 96kPa manifold pressure... even at a high elevation, you'd expect more than that with a boosted engine.

    What MAP sensor are you using? What elevation are you at?

  7. #17
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    Quote Originally Posted by Supercharged111 View Post
    I'm kinda curious if there isn't just a bad handoff from the idle stuff to the VE. Either way that requires VE to be correct. How can I know if my calculated IFR just isn't jiving with the tune?
    The VE is very forgiving towards bad injector data... you can use any junk injector data and then bend the VE table to work with it. The MAF is not so forgiving... use bad injector data and you'll never get the MAF to work right.

  8. #18
    Joe (Moderator) joecar's Avatar
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    lol, that's what I thought

    I look at everything, I learn alot from it (and I don't mind), and I'm not going to let lack of time deter me

    statesman is right, I have so many things going all at once (family health, job, 2nd job, upgrading my Trans Am, EFILive, keeping up at LS1tech, sleep) but I can't give up any of them.
    Last edited by joecar; June 20th, 2017 at 06:17 AM.

  9. #19
    Joe (Moderator) joecar's Avatar
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    +1 what statesman said about VE and MAF tables... and the place where you see it show up the most/worst is at idle.

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    I'm at 6000' so a typical day is 77-79kpa. I believe that puts me in the ~3.5# boost range on something that claims about 5# at sea level on a stock engine. Mine has a freer flowing intake manifold and exhaust setup than stock. Cam is very close to stock, just has a smidge more duration and lift but better airflow nonetheless. I'm not sure how significant of an impact the elevation should have on a mildly boosted engine. Here's the MAP that I used, ACDelco 213-1631 from a Supercharged Cobalt I do believe.

    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    I should also mention the only injector data that I changed was IFR, everything else I left as it was.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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