"The BIG BOV thread" (Where all bov question threads get merged) - Page 517
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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 Timmmy cause a bov shot my dog and stole my truck bov killed my dog 2...

  1. #7741
    Registered User WRXED06's Avatar
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    Quote Originally Posted by Timmmy View Post
    cause a bov shot my dog and stole my truck
    bov killed my dog 2

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  3. #7742
    Registered User D0WNxSH1FT's Avatar
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    In the future please use the SEARCH function for these type of questions.

    Lets use a simple math problem to explain this.

    Intake brings in 10 units of air. MAF sensor tells the ECU that 10 are coming.
    BOV releases say 3 units of air.
    therefore only 7 units of air are sent into the engine.
    ECU sends in 10 units of gasoline thanks to the MAF sensor reading.
    There are now 3 units more of gas in the engine.

    You are running rich. This causes poor idle, pausing between shifts, etc.
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    But it sounds so cool, yO. Gots ta get me one of dem.



    J/k.

  5. #7744
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    I think it is interesting that people don't usually talk about the down side to the OEM BPV. When the PBV opens, it is releasing air that has all ready been sent through the turbo and heated up, and puts it right back in front of the turbo to be heated up again.

    On older WRX's I don't think a 100% Atmo dump valve is terribly bad. Yes, you are releasing air that has been metered, but how long do you think it takes the computer to catch up? Most likely a second or less I would think.

    Now, on the 2006 + WRX, the tuning and fact that they have air injection you have to run 100% recirc. or you will run into idle issues.

    I think that you are fine using a 50/50 BPV on the 2.0 liter WRX's. I have been using one for about 10,000 miles with no issues at all with idle, etc.
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  6. #7745
    Registered User SWRX's Avatar
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    no problems with shifting/idling if you have a 5EAT

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    Quote Originally Posted by 04.SPT.WRX View Post
    Your engine's best friend:


    Ftw!!!
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  9. #7748
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    Quote Originally Posted by scubynubie View Post
    I think it is interesting that people don't usually talk about the down side to the OEM BPV. When the PBV opens, it is releasing air that has all ready been sent through the turbo and heated up, and puts it right back in front of the turbo to be heated up again.
    That "hot" air is already metered and accounted for as you are closing the throttle plate - this air is not running under a significant load where hotter temps would be considered more of an 'avoidance of knock' issue. The goal here to to be sure that the air/fuel mixture is proper so that it is more completely comsumed in the ignition-combustion process. The goal being to avoid issues such as cylinder wash which lead to increased resistance, temps, and oil consumption.

    Quote Originally Posted by scubynubie View Post

    On older WRX's I don't think a 100% Atmo dump valve is terribly bad. Yes, you are releasing air that has been metered, but how long do you think it takes the computer to catch up? Most likely a second or less I would think.

    Now, on the 2006 + WRX, the tuning and fact that they have air injection you have to run 100% recirc. or you will run into idle issues.

    I think that you are fine using a 50/50 BPV on the 2.0 liter WRX's. I have been using one for about 10,000 miles with no issues at all with idle, etc.
    Do you have an A/F gauge with wideband sensor? If not you cannot make this claim as you have no way to measure the results. If you do though - please let us know what you have seen. I am very curious about the resulting ratios off throttle when the pressure is equalizing.

    Everything I have read however with MAF states that BOV's are a bad idea - using a partial mix is simply partially correcting the issue. In real world driving, I'm sure there are plenty of moments where you are going to run a bit richer than you should, the thing is you want to minimize that type of thing. You also certainly don't want this occuring any more because of a BOV - an item which does not add much in the way of performance (vs a BPV) and simply makes noise.
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  10. #7749
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    First, my point with my post was basically to say that this isn't such a simple issue as BOV's are bad, the devil, etc... There is a lot going on here, so there is more to be considered than just the MAF sensor.

    Quote Originally Posted by Micah View Post
    Do you have an A/F gauge with wideband sensor? If not you cannot make this claim as you have no way to measure the results. If you do though - please let us know what you have seen. I am very curious about the resulting ratios off throttle when the pressure is equalizing.
    Well, not really. I can make my argument, as we are just basically ďbench racingĒ here any way, and you can agree or disagree. These are all just hypothesis anyway, and there hasnít been much testing done either way. I will however say that I have done a lot of testing on my car (you can see in my sig), and this has never been an issue. Though keep in mind that I am using a 50/50 BOV.

    Quote Originally Posted by Micah View Post
    Everything I have read however with MAF states that BOV's are a bad idea - using a partial mix is simply partially correcting the issue. In real world driving, I'm sure there are plenty of moments where you are going to run a bit richer than you should, the thing is you want to minimize that type of thing. You also certainly don't want this occurring any more because of a BOV - an item which does not add much in the way of performance (vs a BPV) and simply makes noise.
    You are correct that if you have a MAF, and only a MAF, that BOVís can cause some issues with idle especially. The trick is that the WRX has a MAF, and a MAP sensor, so it is looking at two different sets of information. (when you are reading live boost from your Access port, this is where it gets that information, directly off the throttle body) So when the pressure drops on your intercooler, the ECU will know that, and should be able to compensate at least somewhat. Now you will certainly run rich with a BOV regardless, but as you mentioned, the throttle plate is closed because you are off the throttle. So you arenít injecting much, if any fuel into the cylinder at that time, so you may run rich for a second, but not so much that you will be getting large amounts of gasoline past your rings and into your oil.

    Basically, I guess what I am saying is that I think there should be more discussion about this issue rather than just saying that they are bad, period.
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  11. #7750
    Registered User D0WNxSH1FT's Avatar
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    It is BAD, period. Please do not try to confuse people with theories. It is a proven fact that a BOV on a WRX causes a rich condition which is bad and the only reason people buy them is for the sound.
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  12. #7751
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    Quote Originally Posted by D0WNxSH1FT View Post
    It is BAD, period. Please do not try to confuse people with theories. It is a proven fact that a BOV on a WRX causes a rich condition which is bad and the only reason people buy them is for the sound.
    Okay, why does it cause a rich condition? Proven by who?
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  13. #7752
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    Quote Originally Posted by scubynubie View Post
    Okay, why? Proven by who?
    Proven by countless tuners who can see on their laptops that it causes a rich condition. Just like how a cold air intake on a WRX causes a lean condition. These arent theories, these are facts and I dont want new members to come and read your idea and then say oh well, let me get a bov b/c there is a slight chance it isnt as bad as everyone thinks.

    Feel free to investigate further the effects of a BOV on the WRX.
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  14. #7753
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    Quote Originally Posted by D0WNxSH1FT View Post
    Proven by countless tuners who can see on their laptops that it causes a rich condition. Just like how a cold air intake on a WRX causes a lean condition. These arent theories, these are facts and I dont want new members to come and read your idea and then say oh well, let me get a bov b/c there is a slight chance it isnt as bad as everyone thinks.

    Feel free to investigate further the effects of a BOV on the WRX.
    You are certainly entitled to your oppion, just as I am. But I won't conceed that I am wrong, especially if you can't offer up any documentation...

    Keep in mind that my theories are based on my experience using the part too, so there is a reason behind them.
    Last edited by scubynubie; 11-10-2006 at 11:27 AM.
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  15. #7754
    Registered User Ballz's Avatar
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    Quote Originally Posted by D0WNxSH1FT View Post
    Proven by countless tuners who can see on their laptops that it causes a rich condition. Just like how a cold air intake on a WRX causes a lean condition. These arent theories, these are facts and I dont want new members to come and read your idea and then say oh well, let me get a bov b/c there is a slight chance it isnt as bad as everyone thinks.

    Feel free to investigate further the effects of a BOV on the WRX.
    +1 million

  16. #7755
    Registered User SixDaysToSunday's Avatar
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    BOV - BAD IDEA

    Kids do it for the sound, theres no performance increase, in fact my buddy took a trip to Watkins and w.o his BOV did a quarter mile in 13.9

    With BOV, he did a quarter mile in 14.3

    .4 second difference is enough for me, it's NOT going on my car
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