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Thread: Turbo TBSS 510/540. Power falling off?

  1. 10-29-2011 #1
    deenasty
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    Turbo TBSS 510/540. Power falling off?

    So I had to get the truck tuned. Two bar tune. I have attatched the file, and a scan of the dyno graph. The power seems to drop off after 5300 rpm. It seemed like it likes timing up top, but tuner was afraid to give it anymore than 12-13 degrees. We also noticed that the boost peaked at 10lbs and dropped off like 2lbs up high. Being that my boost controller is not RPM based, there is not much we could do. Im also experincing a little bit of turbo lag/dead peddle down low when I stab it. Its like it downshifts but doesnt really go, until the turbo spools. Is there anything I can do to help the turbo response? Thanks Guys!
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  2. 10-30-2011 #2
    carlrx7
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    iat's or out of cam..
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  3. 10-30-2011 #3
    Nmbr1GMfan
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    What valve springs?
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  4. 10-30-2011 #4
    deenasty
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    IAT's were between 80-120. The cam is a PCMFORLESS Attitude Cam. As for springs, they are PRC .650's.
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  5. 10-30-2011 #5
    Nmbr1GMfan
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    I run around 16 deg on a boosted LS2 and 93 at your inlet temps and no issues.
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  6. 10-30-2011 #6
    IDRIVEAG8GT
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    Noticed this going on when someone didn't turn COT off. I'd review your tune but I'm on my phone and that just ain't happening.
    Gray Ghost- The abomination. 2007 Chevrolet Silverado CCSB. 98mm turbo, nitrous, 428LSX, Rossler 80E with a brake. Finally finished. 23 psi, no numbers, Slow as hell.

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  7. 10-30-2011 #7
    carlrx7
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    how much overlap does that cam have? plot it against speed, trans/converter might be slipping
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  8. 10-30-2011 #8
    Speedmaster747
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    I think the cam might be the issue, that cam was developed for best NA performance, maybe the overlap or lift is the incorrect for boost.
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  9. 10-30-2011 #9
    deenasty
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    Im not sure on the overlap. Yes, it isnt SPECIFICALLY designed for boosted setups, but Alvin at pcmforless said it would work.

    I have attatched another log. There is one good stop/full throttle stab towards the middle of the scan. Does it look lean to you guys under boost? I also noticed quite a bit of timing in her down low and semi-lean condition perhaps giving me this "dead pedal" feel? Tell me what you guys think!
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  10. 10-30-2011 #10
    c.u
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    i`f it was mine i would stop the full throttle run`s.
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  11. 10-30-2011 #11
    deenasty
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    I have not done anymore wot pulls since I noticed the lean condition. Althought it was tuned yesterday, it was not lean on the dyno.
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  12. 10-31-2011 #12
    smokeshow
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    What turbo? I see that all the time with turbos that are too small...
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  13. 10-31-2011 #13
    deenasty
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    Turbonetics t-76 ball bearing with a 1.15 AR
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  14. 11-15-2011 #14
    gn2beatu
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    Looks like your not entering PE mode til 4500, I would enable that to your torque converter stall minus 200 rpm. So if 3600 converter, set it to 3400. Then just richen up your PE by RPM where needed.
    Last edited by gn2beatu; 11-15-2011 at 12:48 AM.
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  15. 11-15-2011 #15
    Mike@G-Force
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    Valve float! Needs more spring pressure.
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  16. 11-15-2011 #16
    gn2beatu
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    I thought I saw he had .650 springs?? What is the cam lift and what rockers?
    2000 Regal GS ~ 3.25 Pulley ~ Headers ~ 3"ex ~ 1.85 Rockers
    Sold 06 TBSS ~ Front Mount T88 ~ 0-30 in 1.17 ~ 0-60 in 3.0
    Wanted ~ Engine-less 95/Older 4x4 ~ Jeep/S-10/Ranger for TT Project
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  17. 11-15-2011 #17
    carlrx7
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    .650 only means that's how far it can compress till it binds.. seat pressure is key, if you have any more than .020 of head room on the lift, then add some shims..

    -Carl
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  18. 11-16-2011 #18
    IDRIVEAG8GT
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    I think it's time for a YouTube clip so we can listen to the exhaust note on a WOT dyno run.
    Gray Ghost- The abomination. 2007 Chevrolet Silverado CCSB. 98mm turbo, nitrous, 428LSX, Rossler 80E with a brake. Finally finished. 23 psi, no numbers, Slow as hell.

    PBM G8- Aluminum 364, twin Precision 67/66 turbos, 6L90 trans swap, CTS-V/Vaporworx fuel system, slowly making progress.

    Dads 2011 CTS-V- Stock bottom end, stock heads, LS9 cam, pullies, ported blower, ported TB, D3 goodies, and lots of nitrous.
    618/618 motor
    906/862 spray

    Caterpillar 50 Forklift- Duramax swap
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