Bad boost fluctuation 2003 wrx
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This is a discussion on Bad boost fluctuation 2003 wrx within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hey guys how's it going. I've got a 2003 wrx and I just put the Cobb 3" turboback exhaust on ...

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    Bad boost fluctuation 2003 wrx

    Hey guys how's it going.

    I've got a 2003 wrx and I just put the Cobb 3" turboback exhaust on a few weeks ago. Before I put the exhaust on I was getting a tiny bit of boost creep(I think that's what it's called). It would over boost to about 13.5 then come back to 10 and stay there, which is where it usually is. After I put the exhaust on it got a little worse, over boosting to 15, dropping to 7, then going back to 10. The other night I noticed that the boost is starting to fluctuate really bad. Mostly happens in 4th and 5th gear at wot and in 2nd and 3rd if I'm at 3k rpm and then go wot. It will over boost to 15, drop to 7, then bounce between 7 and 13 all the way to redline. Yesterday the car started to not go above 5 psi in 1st gear.

    I've looked at all my hoses and they are all fine as far as I can see. I took it to a mechanic and they blamed it on my gauge, but I disagree because I can feel the boost going up and down. I haven't been able to get a firm answer from anyone, but so far the things that have been suggested are the wastegate, the bpv, or maybe a tune.

    I plan to get the car tuned soon on a dyno but I wanted to make sure I fixed this problem first. I will be getting a new digital boost gauge soon so I can make sure that it's not the gauge, but again I don't think that's the problem.

    The only mods on the car is the turboback and a drop in filter

    Any help would be greatly appreciated, so far I haven't been able to figure anything out, even from my Subaru mechanic.

    Thanks!

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    Master Baiter EJ257's Avatar
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    You're experiencing a boost oscillation. It is likely the boost control system doing its job (without a datalog, you can't be sure). Basically, it senses an overboost, reduces WGDC, boost drops, it senses underboost, adds WGDC, boost rises. This process repeats.

    If your vacuum lines are all in working order and you have everything else in line, a tune should fix that problem.
    2005 WRX STi (Mods | Virtual Dyno)

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    Could this be caused by the bigger downpipe? I went from the stock Downpipe to the bell mouth 3"

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by Dakyn
    Could this be caused by the bigger downpipe? I went from the stock Downpipe to the bell mouth 3"
    Yes
    2005 WRX STi (Mods | Virtual Dyno)

    Resident Tuner @ WTF Tuning, LLC

    "Never trust anything that bleeds for a week and lives ..."

    UNYSOC

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