"The BIG BOV thread" (Where all bov question threads get merged) - Page 619
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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; Originally Posted by chris747 i have a greddy type s as well just sitting here, and im also thinking of ...

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    Quote Originally Posted by chris747 View Post
    i have a greddy type s as well just sitting here, and im also thinking of getting it installed on my STI (mods is only an open downpipe).

    i already talked to a shop about a custom flange.

    one question, do you have that greddy BOV recirc or VTA?
    i went to home depot and got a short plastic pipe from the plumbing section. It threaded right into the BOV and cost only like 30 cents.
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    Registered User Metallus's Avatar
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    i need some help deciding

    im looking to get a new BOV just as a noise maker for now but, i also plan on doing a turbo swap within the next year so its going to be necessary anyway. ive pretty much decided on an HKS SSQV. does anyone know of any faults in these? ive also heard rumor that they've been discontinued, is that true? also, could someone please point out the difference in these two BOVs <http://www.maperformance.com/store/home.php?cat=511> i know that one is two stage while the other only has one to hold higher boost/HP, but does one have a distict advantage over the other? price isnt a problem in deciding. thanks in advance for the advice.
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    Sammich Makin' Pwincess wrxtreme06's Avatar
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    from what i hear, BOV's are really bad for your car. ive heard they make you run rich and will cause you to backfire. if youre just looking for noise, do a snorkus delete and change or air filter/get a short ram intake.

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    Registered User sti 701's Avatar
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    Quote Originally Posted by Metallus View Post
    im looking to get a new BOV just as a noise maker for now but, i also plan on doing a turbo swap within the next year so its going to be necessary anyway. ive pretty much decided on an HKS SSQV. does anyone know of any faults in these? ive also heard rumor that they've been discontinued, is that true? also, could someone please point out the difference in these two BOVs <http://www.maperformance.com/store/home.php?cat=511> i know that one is two stage while the other only has one to hold higher boost/HP, but does one have a distict advantage over the other? price isnt a problem in deciding. thanks in advance for the advice.


    ive nothing but good stories from the aps. you could check them out
    and tial thats a big one too

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    Quote Originally Posted by wrxtreme06 View Post
    from what i hear, BOV's are really bad for your car. ive heard they make you run rich and will cause you to backfire. if youre just looking for noise, do a snorkus delete and change or air filter/get a short ram intake.

    im assuming your refering to "atmospheric" BOV's. which are fine if you tune them. "indirect tuning" as im told. i would not get a atmospheric unless i was going to have someone tune my car.

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by wrxtreme06
    ive heard they make you run rich and will cause you to backfire.
    Due to the placement of the MAF sensor

    Quote Originally Posted by wrxtreme06
    if youre just looking for noise, do a snorkus delete and change or air filter/get a short ram intake.
    +1

    The silencer delete + K&N filter will cost ~$100, it's easy to do yourself, and it won't cause the issues that a VTA BOV will. It will not be as loud as some aftermarket BOVs, but I haven't heard the negatives about this method.



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    hey guys I read through as many pages as I can but 600 smething pages is a lot to go through lol

    so is a bov good to run with a stock turbo? and I read something about someone doing something to the stock BPV to make it work like a BOV is that possible? if so is it a bad thing to do? also at what RPM does the boost kick in? in a MT and a AT?

    thanks

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    Geriatric Ginger Mod Rogan's Avatar
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    Quote Originally Posted by matt duarte View Post
    hey guys I read through as many pages as I can but 600 smething pages is a lot to go through lol
    so is a bov good to run with a stock turbo?
    Hi Matt.. answered on pg1.. No. edit: It's not the turbo that is the issue. It's the engine management and air metering, that is the issue. you dump out already metered air, that the ecu is fueling for, thus giving you an overly rich condition. THAT, is what is bad.
    and I read something about someone doing something to the stock BPV to make it work like a BOV is that possible?
    yes, disconnect/plug the return hose from the BPV.
    if so is it a bad thing to do?
    YES.
    also at what RPM does the boost kick in? in a MT and a AT?

    thanks
    Whats the tacho tell you? Boost "begins to kick in" as soon as the engine is placed under load. Where does it reach full boost? Depends on many factors, but usually around 2000-2500..
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    Question Bov

    I have an 05 wrx and i here it is a bad idea to get a BOV for it, is that true and why is that if it is true??

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    From "Unabomber" on NASIOC:

    Blow Off Valve FAQ

    Term usage: "Blow off valves" go by several names, among them are compressor bypass valve (CBV), air by-pass valve, bypass valve (BPV), blow off valve (BOV), Diverter valve, and possibly a few others. BOV is the common and incorrect term that lumps true blow off valves and bypass valves under the same term. For the sake of correctness, this post will refer to either aftermarket BOV, aftermarket BPV or OEM BPV as these are the most correct terms.

    What is the function of a blow off valve (BOV)? To release pressure from the intake tract of a turbo car when the throttle closes. It is a vacuum-actuated valve designed to releases the air to the atmosphere.

    What is the function of a bypass valve (BPV)? To release pressure from the intake tract of a turbo car when the throttle closes. It is a vacuum-actuated valve designed to recirculate the air back into the intake before the turbo inlet, but after the airflow sensor.

    What is the purpose of a BOV/BPV? When the throttle closes and the intake system is under pressure, the high-pressure air entering the motor will bump into the closed throttle plate, and in the absence of a BOV/BPV, a pressure wave will travel back to the turbocharger. The result is that the compressor wheel will stall (a phenomenon known as “compressor surge”) and slow down very quickly. This is hard on the bearings and decreases the turbo’s lifespan, but it also means the turbo will take longer to spin up the next time the throttle is opened.

    Are aftermarket BOVs necessary with Subaru turbos? No. The OEM BPV is perfectly fine up to 20psi of boost. For applications using higher boost levels, an aftermarket BOV/BPV should be considered.

    Can I mod my stock BPV to hold higher boost? Yes. This link gives detailed instructions on how to do so.

    Is the STi BPV better than the WRX BPV? No. They are the same. However, the JDM STi BPV will hold more boost as it is physically different than both the USDM STi BPV and the WRX BPV. The specific PSI rating of the JDM STi BPV is unknown, but users have reported it is good up to 25 PSI.

    Is an aftermarket BPV better than the stock BPV? No. Unless you are considering an aftermarket BPV solely for the purposes of holding higher boost levels. An aftermarket unit should sound just like the OEM unit.

    Which manufacturer is best? This topic is highly debated. There have been no reported consistent "bad" aftermarket BOVs. Obviously, there may have been bad ones sold, but not enough to report as "bad" overall.

    What are the different types of aftermarket BOVs/BPVs? Different manufacturers use different methods. There are three basic types:
    1. Aftermarket BPV: Similar in function to the OEM BPV where 100&#37; of the air is recirculated.
    2. Atmospheric BOV: 100% of the air is vented to the atmosphere.
    3. Hybrid BOV: These depend on the manufacturer and end user settings. These can either be adjustable or manufacturer set for different percentages of atmospheric/recirculation dumping. They can also be set to work as recirculation during lower boost conditions and 100% atmospheric during higher boost conditions.

    Are there any downsides to aftermarket BOVs? There have not been significant amounts of problems with BOVs. Aftermarket BOVs can and do require some light end user maintenance to keep them performing perfectly. For aftermarket hybrid BOVs that have end user defined settings, there will be an initial period of adjustment to obtain the desired recirculation/atmospheric ratio. As well, most aftermarket BOVs will require "tuning" (usually via supplied washers, a screw, or other mechanism on the BOV itself) to allow them to idle correctly and blow off at the right time.

    Are there any negative effects with aftermarket BOVs? Yes. The downside of releasing the air to atmosphere is that it has already been metered by the mass air sensor, and when it 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.

    Can my tuner or engine management tune out this rich period? No.

    Where do I buy aftermarket BOVs/BPVs? Every Subaru/Import performance store sells BOVs. For purchasing, support your local economy or the NASIOC Vendors.

    How hard is it to install aftermarket BOVs/BPVs? Allow around 1 hour for install time. Professional installation, depending on your area, is around $75. This is one vehicle modification that is very simple and can be successfully accomplished by even the greenest shade tree mechanic.

    How do I install BOVs/BPVs? Refer to the BOV/BPV manufacturer's instructions. For BOVs/BPVs without instructions, below is a link to one of the better known installation instructions:
    scoobymods.com instructions (with photos)

    Editors Note

    My thanks to Dan of Mach V Motorsports for writing an excellent BOV article that provided a lot of the information contained within this FAQ. He also provided additional information that was helpful in the formulation of this FAQ.

    This post was created because I wasn't able to find a good blow off valve FAQ. I came up with the text based on LOTS of searching here. Upon reading this you should have an idea of whether a blow off valve best suits your needs or not. The manufacturer is up to you.

    If you find an error in this FAQ, please PM me with factual details and I will update this post. Responses such as, "I have XXX's blow off valve and it's great!" or "XXX's blow off valve broke after 1 month" are not appreciated here, that is what the Car Parts Review Forum is for.
    Last edited by encryptedzion; 12-07-2007 at 07:42 PM.

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    Question question..

    It says a recirculated bpv/bov is pretty much the same as the stock one so wouldnt there be no problems?

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    An aftermarket BPV or recirculating BOV plumbs the air back into the system, like a stock BPV, but it can hold more boost pressure. It won't have any negative effects like a vent-to-atmosphere BOV.
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    if you have a bov and you dyno tune your car is it still making your car run too rich or should the tune fix all of that

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    Quote Originally Posted by Pat'swrx View Post
    if you have a bov and you dyno tune your car is it still making your car run too rich or should the tune fix all of that
    See the post three entries above your post in this thread.
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    Registered User sti 701's Avatar
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    Quote Originally Posted by Pat'swrx View Post
    if you have a bov and you dyno tune your car is it still making your car run too rich or should the tune fix all of that

    Suposedly there really is no way to tune for that. you have to tune it "indirectly". but yeah, if you brought your car to a tuner he could smooth it out.

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