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Old 11-30-2009, 04:51 PM   #201
Subee05
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Thanks for the info. Been considering getting an atmospheric bov but this changed my mind. Is it normal on an sti to be able to barely hear the bpv if the radios off and all?
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Old 11-30-2009, 04:56 PM   #202
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Yes, you will almost never hear it. If you're running some type of intake, you'll hear it more though. I had an Injen CAI on my car for a couple months, and it almost sounded like I had a BOV.
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Old 11-30-2009, 05:13 PM   #203
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Yea I used to have a k&n typhoon and i could hear it alot. All I have now is a catback exhaust. If I turn the radio off and roll my windows up, I can BARELY hear it but I still can. This is normal isnt it?
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Old 12-21-2009, 01:26 PM   #204
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Guys,

Is it unsafe to run the OE Bov 'open to armosphere'? My car is MAP based (Motec) and was mapped with a Forge atmospheric valve. The OE valve just feels sooooo much better, and im running 22 psi
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Old 12-22-2009, 12:08 AM   #205
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thanks for the edu
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Old 12-25-2009, 08:07 AM   #206
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Double posting in the original post, Unabomber:

"I have had XXXX brand valve for years, it has never leaked. How do you know? By looking at your boost gauge? Looking at the boost levels in your datalog? Neither of those prove that the valve isnt leaking. The advice above tells you how to set it and KNOW for 100% sure.

But compressor surge will kill my turbo! Unless its really bad, it really isnt going to kill it.

I have had XXXX brand valve for years, it has never leaked. How do you know? By looking at your boost gauge? Looking at the boost levels in your datalog? Neither of those prove that the valve isnt leaking"

Great write up, thanks for the info.
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Old 12-25-2009, 10:00 AM   #207
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Quote:
Originally Posted by scoobymikeGR View Post
Guys,

Is it unsafe to run the OE Bov 'open to armosphere'? My car is MAP based (Motec) and was mapped with a Forge atmospheric valve. The OE valve just feels sooooo much better, and im running 22 psi
Atmospheric BOV's are FINE with MAP based systems because the intake charge is measured at the manifold, and not at the air filter. This means that only what enters the throttle body into the manifold gets measured for the a/f mixture.

MAF systems read o2 just behind the intake, and unless you recirc this will cause your a/f to be off and you'll dump more fuel than air into the cylinders causing you to run rich.
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Old 02-03-2010, 01:26 AM   #208
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ifl
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Old 02-03-2010, 05:06 PM   #209
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thankyou thankyou thankyou
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Old 02-03-2010, 05:25 PM   #210
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I have a JDM STi swap; I can't find an OE BPV, so can I buy an aftermarket recirculating BOV, such as Perrin or TurboXS?
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Old 02-03-2010, 09:01 PM   #211
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Just get a dang ole OEM USDM BPV as it will work just fine as long as you are running at/under 20ish PSI.
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Old 02-03-2010, 11:04 PM   #212
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Da-Risin-Smoke...of course you can buy an aftermarket BPV w/ recirc...HKS and Greddy now make recirc. fittings/kits for their BOV's.
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Old 02-03-2010, 11:12 PM   #213
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one of the GFB bov's is adjustable on the fly. can have 100% recerc, or vent, or any % in the middle.
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Old 02-17-2010, 04:16 PM   #214
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Hi everyone
Da-Risin-Smoke, one comment I would make is that to the best of my knowledge all aftermarket valves on the market for MY01-current STi engines require a part from the OE BPV in order to recirculate. The part I'm referring to is the recirc outlet which is like a cast 45 degree elbow that bolts to the recirc outlet of the OE valve and all aftermarket valves. Assuming you are running a TMIC, you'll need this elbow to fit any valve type. I mention this to help avoid frustration if you buy a valve and then find you're missing a critical part to install it.

Mekks, you're right about that. The GFB Deceptor Pro is capable of adjusting the venting bias from recirc to atmo and anywhere in between using the in-cabin adjustment dial. You can set it silent when you want it, and loud if you want to be cheeky .

There is also a new valve called the Respons TMS, which can adjust the venting bias in the same way, but it done manually under the hood by hand.

I hope this helps!

Best regards,
GFB Pete
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Old 02-28-2010, 01:07 AM   #215
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For the 2008+ WRX it appears that the O ring is in a machined part in the mounting flange of the factory valve vs being mounted in a machined channel in the TMIC like on a 2006 wrx.

1. So, do the 2008+ valves have a channel machined into them to hold the O ring?

2. If so, can you reuse the factory one or does the factory one fall apart if you try to separate it?

4. If the new valve just has a flat mounting flange, can you just get the OEM gasket that would have been used on a 2002-2005 WRX or 2004-2010 STI?

Thanks!
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Old 02-28-2010, 10:32 PM   #216
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Hi jay25RS,
You're right, the MY08+ WRX valve does have a diamond-shaped o-ring sitting in a channel within the valve's mounting flange.

You can re-use the o-ring on the factory valve, it is only held in by compression and will not be damaged by removing it, unlike gaskets which are usually stuck to one or both flanges (common on the earlier models).

The OEM gasket for the earlier models can't be used on the MY08+ WRX, because the shape and bolt spacing is different. What type of valve are you putting on?

Best regards,
GFB Pete
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Old 02-28-2010, 10:44 PM   #217
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Quote:
Originally Posted by GoFastBits View Post
Hi jay25RS,
You're right, the MY08+ WRX valve does have a diamond-shaped o-ring sitting in a channel within the valve's mounting flange.

You can re-use the o-ring on the factory valve, it is only held in by compression and will not be damaged by removing it, unlike gaskets which are usually stuck to one or both flanges (common on the earlier models).

The OEM gasket for the earlier models can't be used on the MY08+ WRX, because the shape and bolt spacing is different. What type of valve are you putting on?

Best regards,
GFB Pete
Thanks for your response! I'm not sure right now but I know that I want to replace the plastic valve with something umm... not plastic lol... Probably looking at something that is full recirc, I don't need the noise although I'm sure that I'll still hear it once I do the AEM CAI.

Do you have any valves with the channel machined into their flanges?
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Old 03-05-2010, 12:57 AM   #218
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Quote:
Originally Posted by GoFastBits View Post
Mekks, you're right about that. The GFB Deceptor Pro is capable of adjusting the venting bias from recirc to atmo and anywhere in between using the in-cabin adjustment dial. You can set it silent when you want it, and loud if you want to be cheeky .

There is also a new valve called the Respons TMS, which can adjust the venting bias in the same way, but it done manually under the hood by hand.

I hope this helps!

Best regards,
GFB Pete
Obviously a car runs rich when fully atmospheric under stock tune. So how would the ECU know when the BPV is set to atmo or recirculate? Sounds appealing to have incabin dialing too.
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Old 03-05-2010, 10:07 AM   #219
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It doesn't and it never did. Thats the whole point. The ECU has no way of correctly metering how much air has escaped the system regardless of full VTA or 50/50. Once you get back on the throttle the ECU is expecting that air to still be in the system since it was supposed to be recirculated back around behind the MAF.
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Old 03-24-2010, 05:58 PM   #220
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Jay25RS, we do make a Respons TMS direct bolt-on (part # T9001) for the MY08+. It does not have a channel machined into the bottom for the factory o-ring, but it does come with a gasket that performs the same task. In addition to being able to fully recirculate, the Respons TMS does give you the option of venting a percentage to atmosphere should you wish to hear it occasionally.

EtoS, something I’d like to clarify is the term “run rich” – the implication from this term is that the air/fuel mixture is richer than it should be, all the time. That is not actually the case with an atmo-venting valve however, as I’ll cover in more detail.

Quazimoto, you’re dead right, the ECU doesn’t know whether the valve is venting to atmosphere or recirculating, and cannot meter the air that is lost to atmosphere.

However the only time the ECU doesn’t know what’s going on is when the valve is open and venting to atmosphere, which, if the valve is designed and adjusted correctly, occurs when the AFR is not critical. In addition, the amount that the AFR changes is proportional to the amount of air that escapes to atmosphere – i.e. if you vent 50/50, the AFR is not affected as much as it is when venting 100%.

So the two key points are this:

The AFR is only affected when the valve vents to atmosphere, and

The amount that the AFR is affected depends entirely upon how much air is vented to atmosphere.

Let’s look at these two points in more detail. When does a BOV vent? When a well-designed atmo-venting valve is set up correctly, it vents ONLY when the throttle is closed or closing, AND there is pressure in the intercooler to be vented. It is shut at all other times, and when shut, it cannot affect the AFR. In addition, the ECU shuts off the injectors on a closed throttle after about 1 second (as long as RPM is over about 1200), so an atmo-venting valve can only affect the AFR for one second or less, when the throttle is closed after a boost event.

The second point deals with the amount that the AFR is changed during the venting. It’s not like the ECU dumps fuel so the cylinders are swimming in it. When the throttle closes, the airflow drops very rapidly because the turbo is no longer being driven by exhaust, and if you look at the size of a BOV opening in comparison to a throttle body, you’ll see that the amount of air flowing out of it is going to be significantly less than what the engine consumes when on boost. The resulting AFR change is relatively quite small.

The other point here is that AFR is very subjective – a standard Subaru runs very rich at full throttle at high RPM anyway to give a higher factor of safety. Many race cars are tuned to inject extra fuel on a trailing throttle to aid cylinder cooling whenever possible. The small change caused by a BOV then is for the most part, fairly irrelevant.

The above is a whole lot of words, but the reality is that in most cases (depending on the mods and tune of your car) you can vent up to 100% of the air to atmosphere on a Subaru without causing stalling, stumbling, poor idle, excessive fuel consumption or backfiring, PROVIDED the valve is designed, adjusted and functioning correctly. Even on cars where the tuning and mods make it more sensitive to atmo venting, the simple solution is to dial back the ratio of air vented to atmospehre - we've not found one yet that will not run happily with 50% atmosphere venting.

Best regards,
GFB Pete
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Old 05-09-2010, 08:46 PM   #221
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Thanks Unabomber for the informative post. Just bought a 02 wrx and was curious about this.
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Old 07-12-2010, 05:05 PM   #222
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In light of the fact that it sounds as though the part has changed for the '08+ WRX's, here's my ?

I have a 2010 WRX and am being told that the OEM BPV or BOV(whatever your preference) leaks at around 17-18 psi. Is this true? Looking to get my car custom tuned soon and want to know if I need to upgrade this part or not prior to tuning. Also need to determine if running the OEM intercooler on my 2010 is going to be okay at 18-19psi. Hearing stuff about the plastic endtanks not withstanding boost much beyond 18psi. I don't ever plan on running high boost(race fuel), but do want to have a 93 octane map made which will wiststand an additional psi over 91 octane. I will be daily driving on 91. Don't really want to spend another $850 upgrading the BOV and i/c as I'm planning to keep the stock turbo, but just add things like EL headers, up-pipe, intake and EBCS to compliment my TBE and AP.

Anyone pressure tested the OEM BOV in the '08+ to see where it starts leaking? Did this on the eclipse I used to have and the OEM unit held to 23 psi. I gave a way my turbo pressure tester with the last car when i sold it. Guess I could always make another one.
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Old 08-13-2010, 08:49 AM   #223
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Hey all, I've read this FAQ several times, and it seemed basic enough in the past, but as I began thinking about the process of the stock BPV the other day, I couldn't figure out WHY a recirc. BPV is necessary. Perhaps it's so simple that I'm overthinking, but here's my logic (that I hope someone can correct).

Basically, the fact of the matter is that if the air recirculated by the stock BPV were not there (e.g. if it were vented to atmosphere instead, let's say), the engine would temporarily run rich between shifts, right?

However, let's say one is accelerating under WOT and shifts at redline. The air that has entered the intake and pressurized by the turbo was already accounted for by the MAF sensor, so the appropriate amount of fuel is also calculated, but during a shift when one has come off of the accelerator, the throttle plate is closed, and neither that air (which gets recirculated) or the corresponding amount of fuel enters the cylinders, right? In this case, why does the amount of air circulating through the turbo/IC/back into the intake even matter? In other words, why would an engine run rich between shifts when there is no air or fuel (or very little, I should say) entering the engine due to a closed throttle plate in the first place?

Is it possible that the engine runs rich not between shifts, but right after the shift? When the driver then goes back to WOT immediately after the shift, the recirculating air then goes into the cylinders, right? So has the ECU waited to inject the corresponding amount of fuel until after the shift when the driver floors it again? It can't do that, right?

What if instead of WOT after the shift the driver only induces 30% throttle, but the air that initially enters the cylinders was that leftover recirculating air from WOT?

If you can see where I'm getting caught up in the logic, please correct me!

Thanks.
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Old 01-09-2011, 03:08 AM   #224
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So really there is no 100% safe way to replace a BOV for sound, on say a stock 06 wrx?

I understand you can use a 50/50 and it's like "a person on leg braces" but it's not perfect.

Basically, i want a louder BOV but what's the best alternative?
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Old 01-09-2011, 03:24 AM   #225
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Quote:
Originally Posted by HonduhPowa
So really there is no 100% safe way to replace a BOV for sound, on say a stock 06 wrx?

I understand you can use a 50/50 and it's like "a person on leg braces" but it's not perfect.

Basically, i want a louder BOV but what's the best alternative?
1. Buy a Subaru.
2. Remove intake silencer.
3. Catless exhaust.
4. Get a CAI or SRI.
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