"The BIG BOV thread" (Where all bov question threads get merged) - Page 625
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This is a discussion on "The BIG BOV thread" (Where all bov question threads get merged) within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; Unless you're putting down serious numbers, a BOV is unnecessary, and more than likely, more harm than good. A 100% ...

  1. #9361
    Master Baiter EJ257's Avatar
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    Unless you're putting down serious numbers, a BOV is unnecessary, and more than likely, more harm than good.

    A 100% VTA will be worse than the hybrid (50/50). All-in-all, it's your car, and your call. There are countless threads about BOVs on here, so do some research and make your decision.

    Our cars were designed to work with recirculating BPVs. If you want the "PSH!" sound, get a K&N Typhoon SRI or do the silencer delete. Alternatively, go StageII.
    2005 WRX STi (Mods | Virtual Dyno)

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  3. #9362
    Registered User LiquidFIRE's Avatar
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    I agree… I’m pretty new here but I simply put on a SPT SRI and the sound is more then enough. It would not even make sense to put a BOV on the car at this point. No CELs either…

  4. #9363
    Registered User ATCsubie08's Avatar
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    Greddy BOV??

    So generally speaking it seems like BOV's are ineffective and seems like they cause more harm than good. Does a recirculating BOV like the GReddy Type RS Recirculating BOV still have harmful effects on the engine?
    2008 Blue WRX, 5 door...
    First one in the Philly area in Early August 2008 from Concordville nissan/subaru

  5. #9364
    Administrator TheJ's Avatar
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    Quote Originally Posted by TheJ View Post
    A stock WRX/STi comes with a BPV (Bypass valve) which is a vacuum-actuated valve designed to release pressure in the intake system when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake before the turbo.

    An after market blowoff valve does basically the same thing BUT unlike the stock unit it releases air to the atmosphere (giving you the loud sound). Some people see an after market BOV on a stock WRX as being in poor taste (due to the fact that it is purely a noise maker that serves no real function), while others simply find the sound very attractive.

    Opinions notwithstanding, there is a downside to having an after market BOV on a stock WRX. The problem comes when releasing air to the atmosphere that has already been metered by the mass airflow sensor. When the BOV releases (blows off), the ECU will be injecting the wrong amount of fuel into the cylinders. The engine temporarily runs extremely rich (meaning too much fuel is injected into the cylinders). This temporary rich condition isn’t usually THAT harmful, but it can cause bucking or hesitation on lift-throttle. If the condition is really bad, it can eventually foul spark plugs and even clog the catalytic converter as unburned fuel on the catalytic converter burns very hot, and too much of it can melt the cat. Additionally, the rich condition obviously has a negative effect on fuel consumption. The rich condition can not be eliminated by simple engine management or professional tune.


    Links for BOV info:

    Wikipedia

    Unabomber on Nasioc




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  6. #9365
    Administrator TheJ's Avatar
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    Quote Originally Posted by ATCsubie08 View Post
    Does a recirculating BOV like the GReddy Type RS Recirculating BOV still have harmful effects on the engine?
    I don't have experience with that bov specifically but theoretically it shouldn't...

    Michael (AKA; ATCsubie08), why exactly do you want to change out your stock bpv on your stock 2008 WRX?
    Last edited by TheJ; 01-12-2008 at 04:46 AM. Reason: Reduce confusion.
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  8. #9367
    Registered User bigd's Avatar
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    Quote Originally Posted by TheJ View Post
    I don't have experience with that specifically but "theoretically" it shouln't...

    What would be the point though?
    To hold higher boost than stock, or just upgrading a flimsy BPV for one that is more consistent, rugged and dependable.
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  9. #9368
    Administrator TheJ's Avatar
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    Quote Originally Posted by bigd View Post
    To hold higher boost than stock, or just upgrading a flimsy BPV for one that is more consistent, rugged and dependable.
    I 've not heard of many problems with the stock bpv being exceptionally flimsy on brand new, stock WRXs. However, I am aware that an after market part would be needed for "significantly" higher then stock boost levels.

    Maybe my post was too offhand... Perhaps I should have been more specific but I wasn't literally asking the general question "what could possibly be the point of ANY after market BPV". Rather my intention was to ask the member I quoted specifically (who has a brand new, stock 2008 WRX and has made no mention of planned turbo upgrades as of yet) what would be the point "for him".

    It is "possible" he is planning some sort of turbo upgrade that he has not mentioned or he could be somewhat uniquely distrusting of the stock bpv or even perhaps he just wants to dress up his engine bay.

    I don't know, that's why I asked.
    Last edited by TheJ; 01-12-2008 at 08:18 AM. Reason: Tiny buttons on my pda = me typing like a 5 year old
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    Registered User ATCsubie08's Avatar
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    Quote Originally Posted by TheJ View Post
    I don't have experience with that bov specifically but theoretically it shouldn't...

    Michael (AKA; ATCsubie08), why exactly do you want to change out your stock bpv on your stock 2008 WRX?
    For the sound, I like the sound of it and to dress up the engine bay as you put it.. I'm sure when the time comes, if the money is available and there is a turbo upgrade for the new 08's, then I'll be doing that, but I'm sure that time is far off. But after reading all the negative effects an aftermarket BOV can have, I'm shying away from it heavily unless something safe rolls around.
    thanks for the help!
    Last edited by ATCsubie08; 01-12-2008 at 02:30 PM.
    2008 Blue WRX, 5 door...
    First one in the Philly area in Early August 2008 from Concordville nissan/subaru

  11. #9370
    Registered User Micah's Avatar
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    Quote Originally Posted by ATCsubie08 View Post
    For the sound, I like the sound of it and to dress up the engine bay as you put it.. I'm sure when the time comes, if the money is available and there is a turbo upgrade for the new 08's, then I'll be doing that, but I'm sure that time is far off. But after reading all the negative effects an aftermarket BOV can have, I'm shying away from it heavily unless something safe rolls around.
    thanks for the help!
    check the BOV link in my sig
    Torch Red 2002 Chevrolet Corvette Z06 46k mi.
    Black 2002 Subaru Impreza WRX 6-speed 94k mi. my mod list
    10/08/2006 - 14.089@103.01 (5-speed with well worn clutch, no launch)
    "Six stars gleaming, five speeds breaking, four tires chirping, three differentials working, two liters screaming, one turbo boosting... it's what makes a Subaru all-wheel-drive, all we'll drive."
    for Bugeye owners my BOV thread Service Manuals

  12. #9371
    Administrator TheJ's Avatar
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    Quote Originally Posted by ATCsubie08 View Post
    For the sound, I like the sound of it and to dress up the engine bay as you put it.. I'm sure when the time comes, if the money is available and there is a turbo upgrade for the new 08's, then I'll be doing that, but I'm sure that time is far off. But after reading all the negative effects an aftermarket BOV can have, I'm shying away from it heavily unless something safe rolls around.
    thanks for the help!
    If it's sound you want, I don't think you will hear an appreciable difference going with an after market Recirc valve anyway (like the Greddy one were asking about previously). It would sound almost just like your stock bypass valve. That partially lead to my earlier curiosity as to why you wanted one.

    It's venting to the atmosphere (instead of to your intake, as the the stock bpv or a recirc vavle would do) that gives you noticeably louder sound... and some side effects that you may have heard about.

    Not saying you should do this but some people have found that intake silencer removal and/or after market short intakes will enhance the sound from the stock bypass valve.
    Last edited by TheJ; 01-13-2008 at 07:27 AM.
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  13. #9372
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    ...that flutter

    I just bought the GFB stealth bov
    i had no problems installing it

    when i was testing it out,
    at low rpm, i got the flutter noise
    but it sounded great at high boost

    the spring is as loose as can be

    when free rev-ing, the flutter noise does not occur

    is the flutter noise a compression surge or
    is it harmless?
    thanks for the help

  14. #9373
    Registered User Pat'swrx's Avatar
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    Brainfart...what is this called

    so I'm having a brain fart and can't remember the part you remove for a bov...can someone let me know??

    P.S. I need one...whatever it's called

  15. #9374
    Registered User Micah's Avatar
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    many names

    recirculating bypass valve
    bypass valve
    recirculating blow off valve
    Torch Red 2002 Chevrolet Corvette Z06 46k mi.
    Black 2002 Subaru Impreza WRX 6-speed 94k mi. my mod list
    10/08/2006 - 14.089@103.01 (5-speed with well worn clutch, no launch)
    "Six stars gleaming, five speeds breaking, four tires chirping, three differentials working, two liters screaming, one turbo boosting... it's what makes a Subaru all-wheel-drive, all we'll drive."
    for Bugeye owners my BOV thread Service Manuals

  16. #9375
    Registered User Pat'swrx's Avatar
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    YES!!!! thank you!!!

    ...ahhh I feel much better now

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