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Thread: wtf, why am i seeing boost my 1400rpm and 21.6psi by 2100rpm on 13T's?

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    Forum User verified Feedback Score 1 (100%) thor'svr4's Avatar
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    wtf, why am i seeing boost my 1400rpm and 21.6psi by 2100rpm on 13T's?

    to make a long story short i was out today playing around with the boost controller and by 14psi the car was really starting to come alive. i had just turned it up to 15psi when i began a 3rd gear highway pull. around 4500-5000rpm i heard a BANG and for a split second i thought i had blown an ic pipe again. but right as i heard the bang it felt like i was spraying nos, i was almost instantly at redline in 3rd. i glanced at my afr gauge and saw 10.9-11.2 and my HKS EVC read a peak of 21.6psi. no knock on the datalogger. i thought that maybe one of the wastegate vac lines had come off but everything is still on and tight.

    but now i am boosting very early. normally if im in 3rd at 2000rpm and floor it ill see a few psi but i never get to 12-15psi until 2700-3000rpm. for some reason im suddenly seeing small amounts of boost by 14-1500 rpm and 20+ by 2000rpm. my boost controller can sometimes keep it to 15, but every few pulls it just over boost’s like crazy and i see 20+psi.

    what can cause me to spool up so fast?
    and does anyone know how i can steady my boost with the HKS EVC? i reduced my gain to 60% so that i should under boost, but im still over boosting. anyone got any ideas?
    the basic go fast bits...
    forged short block, Billet DR1000's, 680cc injectors, meth inj, FMIC, MAFT, Apexi Neo, hotwired 255lph fuel pump.

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    seize the carpe! Feedback Score 0 Lithium's Avatar
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    maybe you blew a WG Diaphragm. I would check to make sure both waste gates are still working and that the flappers aren't stuck.

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    Forum User Not Verified Feedback Score 0 -dLs-'s Avatar
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    ^---agree with him. A friend of mine had the same problem on his 3s (stock turbos however) and it sounded like a 9mm was fired under his hood. Turned out to be the WG stuck wide open, however we were seeing insane boost numbers (IE no cut off, it would just go up, up, up if you kept your foot into it).

    -dLs-

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    So you're getting 20+ psi at 2100rpm, it spools to redline, and no knock...?

    Whatever it is, I hope you apply for a patent...

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    Forum User verified Feedback Score 1 (100%) thor'svr4's Avatar
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    Quote Originally Posted by -dLs- View Post
    ^---agree with him. A friend of mine had the same problem on his 3s (stock turbos however) and it sounded like a 9mm was fired under his hood. Turned out to be the WG stuck wide open, however we were seeing insane boost numbers (IE no cut off, it would just go up, up, up if you kept your foot into it).

    -dLs-
    there is a good chance the wastegate arm could get stuck with 13T's since you need to remove some bracket material just to install the arm. so maybe my arm just got stuck. but if my arm was stuck wide open wouldnt i not build any boost?

    the car does seam to keep building boost till you let off the gas though, ie the gas peddle controls the boost.

    Quote Originally Posted by RealMcCoy View Post
    So you're getting 20+ psi at 2100rpm, it spools to redline, and no knock...?

    Whatever it is, I hope you apply for a patent...
    i was extremely skeptical at first too. i figured my EVC might be reading the boost pressure wrong or something. as far as i know its impossible for 13T's to spool that fast so if anyone has and ideas on how my EVC could be reading high, or my tach signal is extremely low (even though i still idle at 700-800rpm) or any ideas that can explain what is happening ill look into it.
    Last edited by thor'svr4; 10-24-2010 at 01:58 AM.

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    Forum User Not Verified Feedback Score 2 (100%) jba3's Avatar
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    Run a vac line straight from the ypipe to the wastegates, removing the EBC. SLOWLY and carefully get on it a bit, see if you can boost past 7-8psi. If you can hit 10+ like that, chances are you have a stuck wastegate or two.
    1995 VR4 Coupe

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    Forum User verified Feedback Score 1 (100%) thor'svr4's Avatar
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    Quote Originally Posted by jba3 View Post
    Run a vac line straight from the ypipe to the wastegates, removing the EBC. SLOWLY and carefully get on it a bit, see if you can boost past 7-8psi. If you can hit 10+ like that, chances are you have a stuck wastegate or two.
    that’s actually a really good idea. ill give that a shot tomorrow or Friday. my main issue is that im up at school so its hard to find time and tools to get to work on my car. so ill prob not have a chance to work on the car till Friday afternoon. so far ive found one issue. for 13T's you need to cut off the heat shield mount on the front header so that the waste gate arm will clear. i cracked my old header and replaced it with one i had laying around BUT i never cut the bracket on the new header. it doesnt look like the arm is hitting the bracket but it could be. and that would keep my waste gates from opening and explain the high boost.

    i still dont understand why it would happen suddenly, or why im boosting so soon in the rev range. my data logger confirms my rpms are accurate so i think ill double check the HKS EVC with a boost gauge i had hidden under my shift boot. maybe my HKS EVC is reading high and thats why i see over 20psi by 2100ish rpm. i KNOW there’s no way 13T's can make that much boost that early, but thats why im seeing on the EVC and the good ol butt dyno is saying that the car pulls stupid hard that low in the rpms. also my wideband is showing me dip in the afr's much sooner while accelerating at partial throttle (~35%).

    ive never heard of this problem so im assuming it has to do with something aftermarket that i messed up, the problem is ive got no idea what i could have done that would effect when the 13T's spool. also i havent been able to track down the source of the 'BANG' that i heard on the highway right when the issue began.

    on a side note, when does everyone else’s 13T's spool by? 2700-3000rpm is when they should really start to pull, right? what vac are you at while cruising on the highway in 4th gear? if im cruising and not accelerating or applying any throttle (steady 22ish percent TPS) im at -2.2psi and under as light of an acceleration as i can in 4th at 65mph im at 2-4psi of boost. i swear i used to see -8 to -5psi under a steady 4th gear cruise and -2ish while lightly accelerating? does that sound about normal? if i try driving in 5th on the highway (even if i have a steady TPS) i am always in boost, which i think is abnormal. right?
    Last edited by thor'svr4; 10-25-2010 at 09:46 PM.

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    Couldn't a bad cat causes these same issues, assuming you have one?

    1991 Dodge Stealth RT/TT

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    Forum User Feedback Score -1 (0%) skater334's Avatar
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    Quote Originally Posted by CCrunner84 View Post
    Couldn't a bad cat causes these same issues, assuming you have one?
    No, read what -dls- posted above


    Quote Originally Posted by Atrosity
    Quote Originally Posted by CandyAppleVr4
    3S's have been turning normal people into mechanics since 1991. =P
    yeah you can say that again

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    Forum User verified Feedback Score 1 (100%) thor'svr4's Avatar
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    hopefully tomorrow i will get to the bottom of this. i turned the boost controller to 8psi and it seams to be able to hold it to a solid 7.8-8psi on the HKS EVC display and 8psi on my boost gauge. im starting to think maybe the wastegates open with more force as the boost level is increased, perhaps causing the wastegate arm to 'wedge' inbetween the heat shield mount and the header causing the arm to be stuck for a moment which is causing the high boost setting to spike and hold a very high boost. i think ill check the wastegates and cut off the heat shield bracket. if that doesn’t work then ive got no idea.

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