"The BIG BOV thread" (Where all bov question threads get merged) - Page 671
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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; That only told me that BOV can be bad it barely said anything about recirculation... if i set the recirculation ...

  1. #10051
    Registered User Billeran's Avatar
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    That only told me that BOV can be bad it barely said anything about recirculation... if i set the recirculation right on the BOV such as a Blitz would the car still run rich?

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  3. #10052
    Administrator TheJ's Avatar
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    Quote Originally Posted by Billeran View Post
    That only told me that BOV can be bad it barely said anything about recirculation... if i set the recirculation right on the BOV such as a Blitz would the car still run rich?
    1) There is a link to nasioc in that link which contains more info on BOVs.
    2) Yes it will still run rich. Note that the problem with after market BOVs that release ANY air to the atmosphere, that has already been metered, will cause an issue. You can not completely get around the "air has already been metered" issue by changing the ratio, unless you put it to 100% recirculate... which basically would defeat the purpose (assuming your purpose is to get the whoosh sound) of having an after market BOV that can vent to the atmosphere, on a basically stock WRX.
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  4. #10053
    Registered User Timdog1650's Avatar
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    If you're running a 100% recirculated BOV, you can set it up to behave just like the stock BPV, but, remember that the spring pressure in the BOV is going to make a big difference in how the valve itself performs. If you keep the spring too tight you may experience compressor surge, which can kill your turbo. If you keep it too loose you will leak boost under heavy load and you'll be costing yourself in the power department. If you buy a full recirc valve and set it up to work EXACTLY like the stock valve as far as spring pressure is concerned (which is what will work best on a stock turbo car), then you need to ask yourself why you just spent a couple hundred dollars on a valve that is doing the same exact job as what you already had installed on the car.

    Edit: You know, the more I think about it, the more I realize why people want to screw with their BOV. It's easy to mod, it's right there on the top of the engine, easy to work on with hand tools, highly visible, it makes an admittedly cool sound when it's 100% atmospheric, it's the trademark of a turbo charged car, and doesn't require any mechanical background whatsoever to work on. Something like TGV deletes, however, requires a whole litany of Subie specific skills and a whole garage full of hand tools to do properly...
    Last edited by Timdog1650; 07-11-2008 at 10:12 AM.

  5. #10054
    Registered User Billeran's Avatar
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    Yea i do like the signature sound i will say that, but it was more of a just wondering than a wow that is all i want lol. thanks for your info guys... ill just wait until i drop a huge turbo in there before then, besides sleeper is more BA

  6. #10055
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    recirculating BOV

    does recirculating BOV go pshhh? if not what is the point for it?

  7. #10056
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    Quote Originally Posted by leonwrx13 View Post
    does recirculating BOV go pshhh? if not what is the point for it?
    There is a link in my sig concerning BOV's - you should read it.
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  8. #10057

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    a qwik google search and here you go:

    A BOV and a DV more or less the same, and perform the same function. The difference in terminology is pretty much meaningless. Where people get their undies in a bundle and/or burned is the issue about venting to atmosphere or not.
    With a closed, MAF-based system (such as my current motor, a 1.8 litre turbocharged Audi), venting to atmosphere will cause the motor to run rich. Period. Venting a BOV/DV to atmosphere simply to make more noise is one of a number of definitions which puts the owner of that car into the category of "ricer". ( flames > /dev/null )

    The ECU meters incoming air via the MAF, and using inputs from the MAF, TPS, MAP (if so equipped), RPM, O2 sensor(s) and who knows what else determines how long to fire the injectors. If any of that metered volume of air is vented to atmosphere, the ECU has no idea that it's lost some air and will fire the injectors long enough to match the volume or pre-metered air. Result? Rich condition.

    And just for a minute, consider what happens a non-recirculated valve is open during normal driving. When not making boost, turbocharged motors live in vacuum. Maybe even enough vacuum to hold the BOV/DV open. Ingesting unmetered, and in 99% of the cases which I've seen, unfiltered air. Sound like a good idea?


    read more:
    BOV (blow off valve) vs DV (diverter valve) - what's the deal, anyway?
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  9. #10058
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    Quote Originally Posted by Micah View Post
    There is a link in my sig concerning BOV's - you should read it.
    thats doesnt help

  10. #10059

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    read the 2nd post it explains them both and the reason why on a subaru turbo car its not recommended to use a vent to atmosphere bov (the one that goes psshhht)
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  11. #10060
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    Quote Originally Posted by Weasel 555 View Post
    read the 2nd post it explains them both and the reason why on a subaru turbo car its not recommended to use a vent to atmosphere bov (the one that goes psshhht)
    i know they r bad. but what about the recirculating once? arent they ok?

  12. #10061

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    leon,
    recirculating ones are ok, Subaru in the USA would NOT use them on there turbo imprezas since 2002 to present if they didnt work correctly.

    otherwise they would look like a very stupid car manufacturer wouldnt you think ?
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  13. #10062
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    Yes, the recirc. valves are o.k. on the WRX, they're actually preferred. The post(s) below explain why this is.

    If you really wanted to use a atmosphirc BOV, you could have your ECU tuned for this, but I don't really think that this is the best way to go.

    The WRX is designed so that the BOV recirculates the air and it does so effectively. I'm pretty sure the link below explains the benefits of using a recirculatory BOV on the WRX, check it out again. There is a lot of good info there.

  14. #10063
    Registered User Feezor's Avatar
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    If sound is all you want then why not just do the intake silencer delete?
    Quote Originally Posted by Timdog1650 View Post
    Personally I think it's a good thing when my trannys suck, but that's just personal preference.

  15. #10064
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    [QUOTE=Homaha_Scooby;2316670]

    If you really wanted to use a atmosphirc BOV, you could have your ECU tuned for this, but I don't really think that this is the best way to go.
    [QUOTE]

    I could've sworn you can't tune for atmos. BOV as the air has already been measured. correct me if im wrong but i doubt that because if this were so, there would be more BOV on healthy wrxs out there.
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  16. #10065
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    Quote Originally Posted by Homaha_Scooby View Post
    Yes, the recirc. valves are o.k. on the WRX, they're actually preferred. The post(s) below explain why this is.
    Not seeing the posts below this, but I guess you mean the other posts above. Regardless, recirculating bypass valves are stock equipment on the turbo impreza, and are perfectly fine.

    Quote Originally Posted by Homaha_Scooby View Post
    If you really wanted to use a atmosphirc BOV, you could have your ECU tuned for this, but I don't really think that this is the best way to go.
    EPIC FAIL - IF YOU DO NOT KNOW WHY THEN YOU NEED TO DO MORE READING TO ACCURATELY UNDERSTAND THE PROBLEMS INVOLVED WITH A BOV AND OUR MAF TUNED CARS.

    The only way to circumvent this is to change the tuning from MAF based to MAP based. Metered amounts of fuel are provided for measured airflow. Compressed Airflow prior to the throttlebody gets diverted to atmosphere with a bov, and back to the intake tract with a bpv. When the air gets released by the bov, the fuel is still provided to the cylinder. This creates an overly rich situation where fuel will strip oil from the cylinder wall and get thrown out with the exhaust stroke, which increases oil consumption as well as friction and therefore cylinder temps. This process can also be felt in certain driving conditions as a small hiccup or even a stall. This is why BOV's are considered bad news for our MAF tuned Subaru's.

    Quote Originally Posted by Homaha_Scooby View Post
    The WRX is designed so that the BOV recirculates the air and it does so effectively. I'm pretty sure the link below explains the benefits of using a recirculatory BOV on the WRX, check it out again. There is a lot of good info there.
    He's right here, though it may seem a bit confusing to some as many people equate a BOV with VTA. In any case, the large blob of a paragraph up there after the bold italicized text should explain things clearly enough. Let me know if I've missed anything or misrepresented anything. I am after all a keyboard/wallet mechanic. I haven't worked on any of my own cars since I started buying imports.
    Torch Red 2002 Chevrolet Corvette Z06 46k mi.
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