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Thread: HELP! Cannot get turbo 4.8 to build boost

  1. #1
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    HELP! Cannot get turbo 4.8 to build boost

    I have a 2006 turbo 4.8 4L80 3600-3800 stall convertor S475 T6 1.32AR turbo 1000cc inj cam springs 2bar OS pump gas 93 twin 450 pumps 3.23 gear 29" tire. Turbo is always been little slow to spool on the street then pulls hard. I know due to CID and turbo size that is to be expected but I cannot for the life of me figure out why when I go to the track I CANNOT get this thing to build boost on the foot brake. Will make 1psi and fall on its face let off the brake and it will creep out to 200-300ft and then take off like a rocket. I'm not sure what I'm missing. Would like someone just to see if my tune is wrong or if I have other issues. Thanks!4-21-17 current.hptTP RED TRUCK.cfg1st pass.hpl2nd pass.hpl

  2. #2
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    S475 T6 1.32A/R turbo on a 4.8L engine and you're confused why you have nothing down low?
    I wouldn't even use that on my 5.7L.
    What made you use that turbo? Do you know how to read turbo maps?
    You would've been better off with a Chinese turbo off ebay with an A/R of half of 1.32.. and half the price.
    Exhaust wrap might help + this https://www.hptuners.com/forum/showt...vid-on-youtube

  3. #3
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    While the turbo is large "1.32 is very large" He should still be able to make some boost on the brake. Have you tried fattening it up, and pulling timing? Running any system that'll pull timing and add fuel on the foot brake is what will make boost. I suggest getting a trans brake and two step and going from there. If that doesn't work, sell the s475 and run a 7675-7868 something in that range . I made 800 rwhp on 17 psi with a sbe ls1 on a 7868. Actually have one laying around at the shop in need of a rebuild .

  4. #4
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    Quote Originally Posted by Dennis5374 View Post
    I suggest getting a trans brake and two step and going from there.
    Yeah.. check the link I put up if you haven't already.


    Should just sell it..
    then focus on getting the right size turbo..
    instead of the one that can make the most power.

  5. #5
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    I'm not into the Chinese turbo craze but that's just my personal opinion, have a Lingenfelter LNC2000 have been trying to get it to work but haven't got it just right. I ended up with this turbo brand new for way to good of a deal to pass it up. Exhaust is wrapped as well.

  6. #6
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    Quote Originally Posted by tbandit10 View Post
    I'm not into the Chinese turbo craze...
    Because the turbos were made in China and you were made in the US and you don't want to support China and want to support USA with your turbo purchase instead?
    Even if you got your turbo for $1, end of the day it doesn't fully suit your needs and engine and your car would be much quicker now if you bought a smaller turbo instead.

  7. #7
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    Well, not knowing what you want to do with the car makes it pretty pointless suggesting changing turbos.

    A bigger convertor and getting the 2 step sorted, or a 50 shot would get it working for drag duties.


    If I got that turbo for a dollar I would use it!

  8. #8
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    it has more to do with standards of machine work and quality more so than origin. But by the way for the people who came here to actually answer my question and not trash my setup the convertor was the issue. Thanks again .

  9. #9
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    Good to hear it's sorted.