Bov Vta - Subaru WRX Forum
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#1 Old 03-24-2010, 01:56 PM
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Bov Vta

So I installed a Perrin Adjustable VTA a few day ago with a boost guage install. Can the BOV hurt the performance of the car? I know these are not required but i do like the sound and it doesnt sound ricey at all. Any info on this. By the way I only paid 160 for BOV.

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#2 Old 03-24-2010, 02:46 PM
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It can cause idle issues as well as in between shift issues, especially at lower rpm shifts. Basically air that the car thinks is being recirculated is leaked out, causing the car to run rich. It basically acts as a massive boost leak for split second.

Harm the engine? No. Harm performance, probably.

-Chris
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#3 Old 03-24-2010, 03:51 PM
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Yah I think I will be reinstalling my stock unit for now. It ildes fine and drive fine, o well. Thanks for the info.

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#4 Old 03-24-2010, 08:02 PM
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i dont know why guys think a BOV will affect idle. it cant because the valve for the blow off is closed. closed equals no leaks, no leaks equal normal idle. you have to shift and make enough boost to open the valve to leak off the excess boost first. as for the shifts its the only time you may feel something. normal driving you have to make enough boost to even open the valve there for normal driving you should be fine. as for racing round and making high enough boost, now you will open the valve and for a split second you run rich. 1. rich isnt bad or harmful to performance when it applies for literally .5 seconds. 2. again you shift in like .5 seconds. you cant hurt anything so dont worry about taking it off. if your at 285/285 id leave it on because you are making high boost when your WOT and then you shift. anything above 17psi will and can cause your stock BPV to wear and even crack over time. leave the performance one on and dont worry. worst your gonna get is a little back fire when the super heated exhaust fumes with more then normal rich fuel condition hits the ambient temp and goes pop.

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#5 Old 03-24-2010, 08:44 PM
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Quote:
Originally Posted by synolimit View Post
i dont know why guys think a BOV will affect idle. it cant because the valve for the blow off is closed. closed equals no leaks, no leaks equal normal idle. you have to shift and make enough boost to open the valve to leak off the excess boost first. as for the shifts its the only time you may feel something. normal driving you have to make enough boost to even open the valve there for normal driving you should be fine. as for racing round and making high enough boost, now you will open the valve and for a split second you run rich. 1. rich isnt bad or harmful to performance when it applies for literally .5 seconds. 2. again you shift in like .5 seconds. you cant hurt anything so dont worry about taking it off. if your at 285/285 id leave it on because you are making high boost when your WOT and then you shift. anything above 17psi will and can cause your stock BPV to wear and even crack over time. leave the performance one on and dont worry. worst your gonna get is a little back fire when the super heated exhaust fumes with more then normal rich fuel condition hits the ambient temp and goes pop.
A vented to atmosphere BOV WILL cause idle issues depending on the type of BOV. For instance I run a Synchronic Synapse BOV (full recirc but it can go VTA), without the anti stall adapter on it, the car idles rough and can possibly stall. It just depends on the BOV.

As for the running rich, it runs rich for I believe two rows? Which, yes as you stated isnt much, BUT it will throw a CEL, Engine bank rich. Which, not only is annoying to see the yellow icon, but it also disables the cruise control and the hill assist in our newer 08/09 models. Running rich for that micro second isnt really going to hurt the car, but it does confuse the MAF sensor to the point where it will always throw a CEL unless tuned properly. The topic has been discussed wayyyy to many times, and a simple search will show it. No offense to the OP, but our cars simply just dont originally like the fully VTA BOV. If youre striving for the sound then either; use it and deal with the CEL, use it and tune it properly or install a new intake (which might also throw a CEL ironically) and maybe even a downpipe to further the sound.

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#6 Old 03-24-2010, 09:22 PM
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1mpluse: Thanks for you first hand knowledge on your experiences.

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#7 Old 03-24-2010, 09:35 PM
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I say go with a 50/50 hybrid one. That way you get the sound you're looking for and it won't drive the MAF crazy since there's still recirc. air going back in. Just my .02 cents.
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#8 Old 03-24-2010, 11:58 PM
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*sigh*

Some bad info in here. Please read these threads:
http://www.wrxtuners.com/forums/f52/...and-bov-28382/
Cobb Ap/ Bov
Longterm GOOD/BAD effects of BOVS
use the search button...

Short of it:
1) BOV's waste perfectly good pressurized and cooled intake air
2) Yes they can cause you to run rich
3) Yes they can hurt performance
4) Yes your stock BPV can handle way more pressure than factory settings
5) Most "50/50" valves are just as bad if not worse than traditional BOV's. It's a good option to no-one

You don't need and you shouldn't want a blow off valve. By the way, they're also illegal.

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#9 Old 03-25-2010, 01:15 PM
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i cant speak about a Synchronic Synapse BOV but from "my" personal experience a standard open/close, on or off BOV will not cause idle issues!! it cant, it physically can not unless it is malfunctioning and or the seal is broken. (which can happen on any valve! even stock BPV valve!) all it is, is a valve that is shut 360 degrees around the valve with a vacuum line attached to the intake manifold. if everything is shut, closed and sealed properly, then it can NOT cause an idle issue period!

MOSC your right about everything you said about 100% BOV. the only thing is the "dont need and shouldnt want part". just to clarify 100% back to intake BPV's are needed and you were talking about 100% BOV's.

i promise from my tuners personal experience there is a limit to the stock BPV. does anyone know for sure? no theres no way to tell. just like 5 speed trannys. there is no set number to not go over so you dont blow your third gear. the stock BPV can handle higher boost then stock. but for how long? no one can answer that. everything will break down, everything will need replaced eventually, and time and time again my tuner has had to cut a tune short for going to high on boost and the stock BPV leaking early and making him lose power. the internal spring wasnt made for plus 18psi boost. can one BPV handle it? yes. can all of them? no.

its better to be safe then sorry. to be on the road or on the dyno and have your stock BPV crack or leak and cause a major problems. it has happened just like 5 speed trannys blowing but it doesnt happen all the time.

back to 100% BOV's im i wrong in saying you can run them and run them fine as long as you move the MAF sensor out of the intake before the turbo and move it after the turbo before the throttle body??

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http://www.wrxtuners.com/forums/f121/2011-wrx-build-31226/
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#10 Old 03-25-2010, 01:40 PM
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Quote:
Originally Posted by synolimit View Post
back to 100% BOV's im i wrong in saying you can run them and run them fine as long as you move the MAF sensor out of the intake before the turbo and move it after the turbo before the throttle body??
Yes, that will fix the issue... That's what a blow-through boost tube does. Puts the maf after the intercooler in front of the throttle body. Basically as long as it's after the BPV/BOV it'll be fine. Why Subaru didn't do that in the first place is beyond me.

-Chris
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#11 Old 03-25-2010, 02:12 PM
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You'd have to put the MAF on the engine side of the intercooler. That's infeasible. No, you can't get around this by moving the MAF. Moving it would require a new tune by somebody way smarter than me to figure out all kinds of new issues that arise from not knowing how much air is feeding your turbo.

A BOV can be tuned around to prevent problems but that will basically be by sacrificing performance to ensure you are safe between shifts.

The stock BPV has been tested and tested again for almost a decade now. It's basically the same design that subaru has used for many years. It can handle 18 PSI without any issue and with simple modification has been shown to hold well in excess of 20 PSI. If you go beyond that, you STILL shouldn't get a BOV. What you want is an aftermarket recirc valve like the one made by perrin. It's still a full BPV and can handle huge PSI (at least 35 PSI).

Look, BPV's make noise too. You don't hear them in the factory car because of the intake silencer. You can remove this part, you SHOULD remove this part (it costs you airflow). You will hear the BPV. No, it won't sound like an air-horn going off but it will actually continue to function.

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#12 Old 03-25-2010, 03:41 PM
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With the AEM CAI on my 08 along with stage 2 22 psi tuning my car is plenty loud fully recirculating like Mosc says. If you want louder then that.....probably should have bought a SRT4. LOL

Brad

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#13 Old 03-25-2010, 04:05 PM
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When it comes down to it, you are talking about the most awesome intake air ever. It's pressurized and cooled. This is primo air you're throwing away. When you first hit that next gear, you'll have a nice surge of response from the turbo rather than the lag of trying to fill up the IC again as well as burn off that excess fuel you just dumped in. Computer stuff aside.

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#14 Old 03-25-2010, 04:08 PM
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I've put on the SPT intake last weekend and my stock BPV is plenty loud now.

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#15 Old 03-25-2010, 04:13 PM
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Quote:
Originally Posted by blk05WRX View Post
I've put on the SPT intake last weekend and my stock BPV is plenty loud now.
Right, because this bypasses the intake silencer in your fender well.

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