Low psi (please help)
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This is a discussion on Low psi (please help) within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I just purchased an '06 WRX and I recently discovered an issue. You guys have probably heard of this one ...

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    Low psi (please help)

    I just purchased an '06 WRX and I recently discovered an issue. You guys have probably heard of this one a few times but I couldn't really find any solid answers. Anyways my boost is only running at 7.5-8 psi and from what I've read it should be near 13. Has anyone ran into this issue and found a resolution???

    Any help will be greatly appreciated.

    -Oakley

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    Sammich Makin' Pwincess wrxtreme06's Avatar
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    how are you monitoring your boost?

    what gear were you in while doing your reading?

    any mods?

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    Registered User poly_poly-man's Avatar
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    Assuming everything wrxtreme said has a reasonable answer...

    Sounds like wastegate boost to me (it'll really be 7psi, but you're either reading high, or have a tightened arm or smth).

    Check all your boost lines, especially the one going to the wastegate. Make sure the BCS is plugged in, check your entire intake and exhaust system for leaks, and look for anything else obvious.

    We'll need your entire mod list, because everything is critical.
    My big thread: The Used WRX Buying Checklist - Please Contribute!

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    It has the stock optional WRX boost gauge that reads from -.15-.15 psi. As far as the mods go it has a catback exhaust and an accessport although I believe that isn't mapped right now. Is running that low of boost bad for the engine?

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    The reading is usually in 3rd and 4th gear. It won't rise past 8 even when floored. I'm trying to take it as easy as possible until I get it fixed.

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    Registered User poly_poly-man's Avatar
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    Running low boost probably isn't bad for the engine, but it's not why you bought the car, right? . Also, it could be a sign of certain other issues (like intake/exhaust leakage).

    You are sure that you're reading the boost gauge correct, right? The positive side is not psi, it's bars iirc. You should be a tad under 1 bar stock. Sounds like you may have figured it out, though.

    Also, watch that the boost line to the gauge itself isn't pinched - if the car feels like it should and you're not seeing the right values, it could be that the gauge is not seeing your full boost.
    My big thread: The Used WRX Buying Checklist - Please Contribute!

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    Ah maybe I'm reading it wrong. From the 0 point it is reading two notches above the .05 mark. So my question is how is this relative to psi? Sorry for the noob questions. Below is an image of the gauge I have.


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    He simply abides. SD_GR's Avatar
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    Quote Originally Posted by neurotivity View Post
    It has the stock optional WRX boost gauge that reads from -.15-.15 psi. As far as the mods go it has a catback exhaust and an accessport although I believe that isn't mapped right now. Is running that low of boost bad for the engine?
    I know of no stock boost gauge that reads in PSI. Check the units on the gauge.

    EDIT: Saw the photo you posted. Your gauge does not read in PSI. It reads in MPa; this is the leading reason why the gauge is labeled "MPa." Your max boost is .08 MPa from what you've said, and that is equivalent to roughly 11.6 PSI.

    Since you have an AP, you can use that to measure boost pressure. I think the AP will read PSI directly. It might be interesting to compare results. So far though nothing described is anything dramatically wrong with the car.
    Last edited by SD_GR; 03-21-2011 at 05:35 PM.
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    Sweet yeah I had to send my AP2 in to get the screen fixed but yeah I haven't seen a gauge that reads MPa so I was basing the psi of the actual number of bars it was reading and not the distance from the .1 bar. I will check the AP reading as soon as it's shipped back from Cobb. With that being said though if it truly is only running 11.6 isn't that still a bit low. I mean it's good to know that its not actually 7 psi but I believe it should be near 13 right? Thanks for the info though, that saved a ton of frustration.

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    Registered User poly_poly-man's Avatar
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    11 psi isn't too bad, but it still could be a boost line pinched, or a minor intake leak or smth. Double check with an AP, definitely.
    My big thread: The Used WRX Buying Checklist - Please Contribute!

    My current car: 2002 WRB WRX Wagon.
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    So I'm thinking you may be right about the leak. When driving at say 2500 RPM's approaching 3k without letting off the gas or pushing in the clutch pedal, the stock BOV sounds like its releasing pressure. At 3500 RPM's when shifting it does the same as it should. It shouldn't release pressure until the foot is off the throttle correct?

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    Registered User poly_poly-man's Avatar
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    maybe that's not the sound of your bpv, but of something else in your intake tract not sealing right? Check it out - it's making you run rich too, if that's what it is.
    My big thread: The Used WRX Buying Checklist - Please Contribute!

    My current car: 2002 WRB WRX Wagon.
    Mods: GM BCS, Carberry SD rom, uppipe, AEM UEGO, Klunk Killer, F+R shifter bushings, head unit

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    Okay so I did a pretty thorough inspection of my intake tract and vacum lines and I cannot visibly see anything that would cause it although it could be somewhere and small enough that I wouldn't be able to see it. I read the DIY "find your leak" tool post and it doesn't seem too hard to make although I don't have a compressor and the soapy mixture he used along with it seems potentially unsafe. I also read the sticky note and I apologize for not posting this sooner but I have an '06 WRX with 73k and no mods. I'm noticing the drop in pressure during while accelerating in 2nd 3rd and 4th gear. I have ruled out all of the possible causes based on research and narrowed it down to a boost leak. Is there any specific test I can do or have done to find a boost leak?

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