Boost fall and surge while accelerating
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This is a discussion on Boost fall and surge while accelerating within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Firstly, I apologize if there's already a thread about this. Currently my browser won't let me use the search tool ...

  1. #1
    Registered User CGimpreza's Avatar
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    Boost fall and surge while accelerating

    Firstly, I apologize if there's already a thread about this. Currently my browser won't let me use the search tool without giving me a "failed request" page.

    Anyhow this is the problem: While accelerating WOT after peak boost has been met, the boost falls off, the surges back up, then falls off again. It's a weird pulsing feeling. Currently I'm running livetune cobb stage 2 93 octane.

    Mods are: HKS uncatted upipe w/o EGT bung
    SR*S turbo back exhausts w/o cats
    turbo XS blowoff valve (that I want to get removed, but have no more cash to do atm).

    anyone experienced this before?
    One day I'll have a truly awesome sig
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    2004 impreza WRX
    uppipe, downpipe, ap, and a grin
    ~Blobeye syndicate~ #2007

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    Registered User dbswagon's Avatar
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    Hey I am having similar issues. I have an 03 wrx wagon with catless TBE and cobb stage 2 91 oct. My car boosts and accelerates fine until 4th where it boost surges slightly and falls and then in 5th where it dramatically boosts and falls from 3,000 rpm and up. I was told by a couple people it was an issue with the cobb ap map but not sure and would love to fix it.

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    Supporting Member mjboudreaux77's Avatar
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    In 5th WOT - my car will surge beyond target, and fall back to where COBB Stage II wants it. When I am about 1/2 throttle in 5th, boost will go to 7psi and start to bounce. If I accelerate or let off the gas, the bounce stops.

    Seemed normal to me.
    If I don't die by Thursday, I'll be roarin Friday night - Jimmy Buffett

  5. #4
    Registered User dbswagon's Avatar
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    That sounds good but mine goes up then down then up then down about 4 or 5 times between 4000 rpm to redline and the acceleration oscillates the same way. It's really weird because I had catless UP and TBE before and ran stage 2 cobb ap and had no problems. The only difference this time is no UP and a different catback section (same diameter piping tho 3" both times). Anybody's input would be great. I've been searching all over for answers to the problem and people only bring it up but I haven't found the reason for it yet or how to solve the problem without getting a full tune.
    Last edited by dbswagon; 04-06-2010 at 10:29 PM.

  6. #5
    Registered User dbswagon's Avatar
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    Mostly just in 5th.. barely in 4th

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    Master Baiter EJ257's Avatar
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    You're having an issue with boost oscillation

    Here's two threads that came up with a quick search for "oscillation":
    Boost fluctuation/surge.
    04 WRX characteristics questions.
    2005 WRX STi (Mods | Virtual Dyno)

    Resident Tuner @ WTF Tuning, LLC

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  8. #7
    Registered User CGimpreza's Avatar
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    Quote Originally Posted by EJ257 View Post
    You're having an issue with boost oscillation

    Here's two threads that came up with a quick search for "oscillation":
    Boost fluctuation/surge.
    04 WRX characteristics questions.
    Cool! Thanks! I honestly didn't know what term to use for it beyond "pulsation" or some such (until I saw other posts in the thread).
    One day I'll have a truly awesome sig
    -------
    2004 impreza WRX
    uppipe, downpipe, ap, and a grin
    ~Blobeye syndicate~ #2007

  9. #8
    Registered User CGimpreza's Avatar
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    Wow...uh...I was tracking my boost on the way to school using my ap. You know for sure somethings really off when you see 19.7 psi. I'm not very handy at all, so I guess it's off to the shop.
    One day I'll have a truly awesome sig
    -------
    2004 impreza WRX
    uppipe, downpipe, ap, and a grin
    ~Blobeye syndicate~ #2007

  10. #9
    Registered User dbswagon's Avatar
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    For me the ap reads the boost a little higher than what my boost gauge says. But also, I just got some new rims and tires. The diameter of my tires are now comparable to stock, whereas before I had 205/40/16 (much smaller) on my stock rims. My boost "oscillations" have gone away completely in all gears. It must be because the ap stage 2 map requires stock tire diameter size for the turbo to boost properly at the correct rpms : )

  11. #10
    Registered User CGimpreza's Avatar
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    My boost has repeatedly flown up to around 19 psi in 4th and above. I'm pretty sure that's -not- supposed to happen (plus I'm on stock wheels ). So I'll have to cross my fingers and pull in to the dealer ( don't have any local subbie experts that I know of around here to call on).
    One day I'll have a truly awesome sig
    -------
    2004 impreza WRX
    uppipe, downpipe, ap, and a grin
    ~Blobeye syndicate~ #2007

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