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Old 03-08-2011, 06:36 PM   #1
xluben
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Default New Forge BPV for 08+ WRX's

OK, let's start this off by saying that if you have an STI or WRX 07 or older, you do not need a BPV. This is well established. The stock one works fine. BUT if you have an 08+ WRX, the BPV (and the TMIC end tanks) are made of plastic. They tend to leak quite easily. Some even at stock boost levels, but more regularly at Stage 2 or slightly beyond (18-20psi starts getting into the danger zone). So if you have an 08+ WRX, and are Stage 2 or further, you're probably looking at a new BPV. This post will apply to you!

Here is a photo of the OEM BPV and TMIC (showing BPV mounting location and seal design).



The Forge BPV is commonly recommended due to the low cost, and good build quality of the unit. It is a fully recirculating valve, so there will be no issues with running rich during shifts. The valve is an extremely solid piece of work. Nothing feels cheap about it (except the price). Up until very recently, all retailers selling Forge BPV's for the 08+ WRX, were simply selling the Mazda version. It uses the same size flange mount, and is adjustable so the hoses can point in the proper direction to mount on the WRX.

The model number is: FMDMAZ3

Here is a link to the product page: http://www.forgemotorsport.co.uk/con...oduct=FMDVMAZ3

I got the black version. Here is a shot of what you get (and a third (blue) spring, which is installed in the BPV for the photo).



Very similar in size and layout to the stock BPV.



The first issue is seen when you look at the seal design of the newer stock TMIC's. The stock valve and intercooler use a diamond shaped gasket seal. The Forge BPV uses a round o-ring seal. The round o-ring does not completely cover the diamond shaped hole in the OEM TMIC, so it does not seal properly no matter what you do. If you want to use the Forge BPV with the OEM TMIC you can either cut a custom flat gasket or seal it in place with epoxy or silicone or some other sealant.



If you have an aftermarket TMIC it will probably work just fine. Most aftermarket intercoolers still have a round mounting point, so the o-ring will seal without any problems.



So assuming you have found a way to mount the Forge BPV onto your WRX (using a gasket or sealant, or onto an aftermarket TMIC) you should be fine right? Kind of, but not really. I had mine on my car for a while, and it seemed just fine. But once I put on an AEM intake, I could then hear a bit of fluttering every time that I shifted under load and partial boost. It wasn't a lot, and it wasn't every time, but it was there. Normally like 3rd, 4th, or 5th gear, usually slightly uphill, boost between 5-10psi. Maybe not a big deal, but annoying none the less. Also, this may not be an issue if you use the BPV on the stock intercooler, because of the decreased air volume.

I recently got the new WRX specific Forge BPV (thanks RallySportDirect!). I was a bit disappointed that it was bright and shiny silver (ugh), so I wasn't even sure if I'd put it in, I figured it would work the same, and it wouldn't look as good. I thought maybe I'd wait and see if they came out with a black one eventually. I was told they always come out with the silver ones first, and then release the same model in black sometime later. This is the new valve that I received.

The model number is: FMWRX3

Here is a link to the product page: http://www.forgemotorsport.co.uk/con...product=FMWRX3

Unfortunately I don't have any photos of the valve, since I did put it in my car. I can tell you that mine does NOT have the bolt down top portion to hold the piston in (as shown on the Forge product page). It uses the same screw clamp style that my other valves uses (see photo above). A collar around the edge screws down and holds the top in place. I think this is better because it allows for complete 360 degree adjustment of the vacuum line nipple.

EDIT: I found that RallySportDirect already has the new valve on their site. Here is a photo of the one I have.



Anyways, I eventually decided to compare the valves side by side. They are the same size and shape, but the new one has a groove milled in to hold the OEM diamond shaped seal. I thought they were the same other than that. The springs are the same force, and the piston looks identical. But I eventually noticed that the hole in the bottom of the valve is larger on the new unit! The increased area acting on the bottom of the piston should increase response time (valve opens more quickly). I don't have a photo of the new valve, but I will try to explain the difference on this photo of the old valve.



If you look at the photo above, you can see a circular groove machined into the base of the valve, around the hole for the piston (the two small holes on either side of the piston, within the o-ring, are not actually holes, they do not go all the way through). The size of the circular groove is the size of the hole on the new valve! It's probably an 1/8th of an inch wider in diameter. This allows quite a bit more air to act on the piston, and therefore increase the force working to open the valve.

EDIT: I found that RallySportDirect already has the new valve on their site. Here is a photo of the one I have.



You can see the groove for the OEM diamond shaped gasket to fit into. Make sure you don't damage this or you'll have to buy a new one from the dealer. The Forge valve does not come with this seal. You can see from this photo that the bottom of the piston looks the same, but the hole for the air to act on the piston is much larger than on my old valve. This allows for a greater surface area for the pressure to act upon. Area x Pressure = Force, so assuming the same boost pressure, there is now more force trying to open the valve. This results in quicker response!


I put the new valve on my car without changing anything else. Same spring (yellow), same TMIC, etc, etc. Went for a quick spin and it now performs perfectly! The flutter when shifting is gone! It seems to respond (open the valve) very quickly. I think this is a good thing because it will help to reduce wear and tear on the turbo. If you want to limit pressure drop when shifting, then this might not be for you. But for most people the new valve is better all around! I am glad to finally be rid of the flutter, and I also think the OEM gasket will seal better than the thin o-ring on the other valve (although this was never an issue).

Hope this info is useful to someone. I have been trying to figure out the flutter for some time now, and I'm happy to see that Forge took care of it with the design of the new valve! Not sure when retailers will have it (maybe they already do), but if you have an 08+ WRX and are looking for a Forge BPV, I would look to get the updated version!

Last edited by xluben; 03-08-2011 at 09:56 PM.
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Old 03-08-2011, 07:06 PM   #2
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The flutter is something you will experiance on the piston style BOV iT's valve flutter. This is what happens when the valve opens and closes very rapidly as the pressure in the bottom side and the top side get very close to equal. Mine does it between shifts under light loads. I have the turbo xs bov. the higher spring rate will eliminate some of it but You will have a less responsive bov.
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Old 03-08-2011, 08:00 PM   #3
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So that's what I'm hearing? The valve fluttering? I thought it was the compressor wheel slowing down due to backpressure. Whatever it is, it seems to have decreased with the new valve design.

Maybe I'll try some different springs. If it gets worse with a harder spring I would assume it's the backpressure causing the compressor wheel to slow down. If it gets better with a stiffer spring, then it does make sense that it's the valve fluttering.
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Old 03-08-2011, 08:25 PM   #4
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The firmer the spring the less you should hear it but The valve Wont be as effective at lower boost.
Remember the hose the attaches to the top or side of the BOV has the full boost pressure under load this is helping hold the Piston down, Then on the bottom of the piston is manifold pressure The same pressure as what pushing down on the Top of the valve, That is why they say add firmer springs or more washers if you are experiancing The piston in the bov lifting at idle causing the rough idle. This is from Vaccum at idle.
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Old 03-08-2011, 08:43 PM   #5
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Yep, under boost the pressure on either side of the piston should be equal. The way the valve is designed has a much larger surface area on the top of the valve, so under boost, the valve should essentially hold it self closed without a spring at all (assuming equal pressure on either side of the piston).

But at vacuum the valve is actually being pulled upwards. This is what the spring is used for. It holds the valve closed at idle, and helps to quickly close it when needed. Really the spring should only have to be strong enough to overcome vacuum pressure. Anything more than that is just slowing down its response.
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Old 03-08-2011, 09:15 PM   #6
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I totally get that and agree 100%. But why does forge recommend stiffer springs with more boost? It really shouldn't matter.
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Old 03-08-2011, 09:18 PM   #7
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Yeah, I don't understand that either. Might be just to try and control valve lift on higher boost setups.

If you look at how Tial specs their springs, it is based solely on vacuum readings:

http://www.tialmedia.com/documents/w3_tial_bovq_sp.pdf

Similar piston design, and this method of spring selection makes a lot of sense to me.
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Old 03-08-2011, 09:29 PM   #8
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That makes more sense to me. So much so I may try installing the weaker spring in my forge valve. If I measure engine vacuum then use a vacuum pump on the valve with it off the car , I should be able to match engine vacuum with the pump and not have the valve open till a few more inches of vacuum. Only down side I can think of is slightly less boost holding In between shifts.
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Old 03-08-2011, 09:41 PM   #9
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That's exactly how I see it. I wish I had a regulated vacuum pump so I could perfectly tune the spring to barely hold the valve closed at max vacuum. I like a valve that responds quickly, and I'm willing to lose a little more pressure during shifts.

Another thing that would be pretty easy to implement would be some kind of adjustable valve lift limiter like the Perrin BPV uses. It is basically just a screw that you lock in place and it only allows the valve to open a certain amount. See page 2 for a cutaway:

http://www.perrinperformance.com/sha.../pspint610.pdf

You could do a screw in the Forge piston, but adjustability would be limited because the piston doesn't have as much material to drill/tap. Unless you drilled all the way through the piston, and then used something to seal the screw in place (ie. set it and loctite it in place). You could also put the screw in the top of the BPV (you'd still have to seal it in place) or even just use some kind of spacer that the piston would bump into before fully opening.

The advantage of this would presumably be; quick response, without the complete loss of pressure. You could perfectly tune the spring to open the valve instantly (and avoid back pressure), while still limiting the airflow (so that you don't loose all of your boost during a quick shift). Seems like a good idea in theory. Not sure if it makes any difference in practice.
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Old 03-08-2011, 09:41 PM   #10
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ZOMG! the Forge valve that has been working on Legacy GT's since 2005 also works on the 2008+ wrx!?!?!






siiiiigh.
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Old 03-08-2011, 09:49 PM   #11
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Quote:
Originally Posted by KurtP View Post
ZOMG! the Forge valve that has been working on Legacy GT's since 2005 also works on the 2008+ wrx!?!?!






siiiiigh.
If I understand things correctly, the LGT uses the same TMIC as the 08+ WRX, but sometime in 08 or 09 the WRX TMIC went from a normal circular seal, to the diamond shaped hole/seal. I'm not sure if the LGT TMIC did the same thing. This makes the Mazda valve no longer a direct "bolt-on". Sure, you can make it work with other sealing methods, but it won't seal with the o-ring and design that Forge intended.

So Forge has been kind enough to come out with a new model with an updated flange that does seal with the newer TMIC's. Along with the seal change, they also updated the airflow/pressure bias on the piston to allow for quicker response of the valve. Something that I found beneficial in my setup. I think the new valve (not the one LGT's have been using for half a decade) is nice improvement over the old one. Both in ease of use, and in performance. That is merely what this post was meant to show.
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Old 03-08-2011, 10:00 PM   #12
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I went through the same thing with the seal on the valve. Everyone I contacted basically just told me to bolt it on I was wrong lol. Thanks for posting up the new valve. I made a gasket for my lgt valve so I'm keeping it for now.
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Old 03-08-2011, 09:53 PM   #13
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My legacy had the diamond shaped hole/seal in the TMIC.

I'm not mad at you for discovering a valve you like. I'm just getting old. And like old timers getting frustrated with kids who don't listen, old timer Subaru enthusiasts get tired of it on Nasioc too. Legacy owner's especially.

From our perspective, we have been talking about what works on these cars since 05 when the LGT came out, and despite us saying so, and despite a thread sticky here saying so, 08+ wrx'ers dont want to listen. The 2008 WRX is nothing more than a 05-09 legacy with difference sheet metal and a different interior. Your car, down to the suspension and subframe, is the same car as a 2005-2009 Legacy GT. A lot of the parts marketed for the 08+ wrx, are in fact, LGT parts.

Again, things move on and change. But the concepts that make a EJ25 USDM turbo motor work are the same things now that they were 5 years ago when they came out, and something even before that with the EJ20. The answers are there.

Obviously share your findings on what you try and inform others, but a lot of 08+ wrx'ers frustration with parts working or not working etc could be solved in 10 minutes of searching on LGT.com.

Just a thought, is all.

Last edited by KurtP; 03-08-2011 at 10:00 PM.
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Old 03-08-2011, 09:55 PM   #14
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Quote:
Originally Posted by KurtP View Post
My legacy had the diamond shaped hole/seal.
Makes sense that Subaru switched all of the TMIC's to the new design in 09. So, which valve to you have? The Mazda one? How did you get it to seal?
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Old 03-08-2011, 10:03 PM   #15
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Quote:
Originally Posted by xluben View Post
Makes sense that Subaru switched all of the TMIC's to the new design in 09. So, which valve to you have? The Mazda one? How did you get it to seal?
I used the same thing I use on all BOV's for any turbo car: a liquid gasket/seal.

I've found that regardless of how it was made, BOV's very frequently require a liquid sealant to work anyway. Esp. when transitioning to a FMIC that doesnt use that ridiculous honey comb/diamond fitting.

The new adapter plate seems like it will work well, though.
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Old 03-08-2011, 10:15 PM   #16
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Quote:
Originally Posted by KurtP View Post
My legacy had the diamond shaped hole/seal in the TMIC.

I'm not mad at you for discovering a valve you like. I'm just getting old. And like old timers getting frustrated with kids who don't listen, old timer Subaru enthusiasts get tired of it on Nasioc too. Legacy owner's especially.

From our perspective, we have been talking about what works on these cars since 05 when the LGT came out, and despite us saying so, and despite a thread sticky here saying so, 08+ wrx'ers dont want to listen. The 2008 WRX is nothing more than a 05-09 legacy with difference sheet metal and a different interior. Your car, down to the suspension and subframe, is the same car as a 2005-2009 Legacy GT. A lot of the parts marketed for the 08+ wrx, are in fact, LGT parts.

Again, things move on and change. But the concepts that make a EJ25 USDM turbo motor work are the same things now that they were 5 years ago when they came out, and something even before that with the EJ20. The answers are there.

Obviously share your findings on what you try and inform others, but a lot of 08+ wrx'ers frustration with parts working or not working etc could be solved in 10 minutes of searching on LGT.com.

Just a thought, is all.
Just saw your edit. I did figure this out by searching after I got the valve and realized it didn't fit. My solution was just to wait until I installed the new TMIC because then it would seal with the o-ring. The point of posting this is so that other people know that there is NEW valve. One that just came out. One that is a bolt on product. One that doesn't require any additional sealant. If the product is designed with a seal, I feel that is what should be used to seal it. If that isn't the case, then the product should not have the seal in the first place, and should instruct users to seal it themselves. Just my opinion.

The main point was to show that there is new product. Secondary point was to note that they actually changed the functionality of the valve (as well as the seal). You have made yours work by sealing it up, but the pressure bias is not the same, so the response is not the same (as the new valve). For some people a slower valve may be better. I'm just trying to let people know there are options. And I actually have found the exact answer to several problems/questions I've had by searching the LGT boards. It just frustrates me that some other WRX owner, that had inevitably already had the same problem as me, hadn't posted it on a WRX board, so I would have found it that much sooner.

Quote:
Originally Posted by Dragonfueled View Post
I went through the same thing with the seal on the valve. Everyone I contacted basically just told me to bolt it on I was wrong lol. Thanks for posting up the new valve. I made a gasket for my lgt valve so I'm keeping it for now.
Exactly why I posted this. I don't think there's any reason not to. Why should a WRX owner have to search a LGT owner's group website, when it would be just as easy to post the same information on a site that is dedicated to Impreza's? And it's a new product anyways. I'd have to guess the the actual info on the new mounting flange probably isn't on the LGT boards yet (but maybe it is).

Quote:
Originally Posted by KurtP View Post
I used the same thing I use on all BOV's for any turbo car: a liquid gasket/seal.

I've found that regardless of how it was made, BOV's very frequently require a liquid sealant to work anyway. Esp. when transitioning to a FMIC that doesnt use that ridiculous honey comb/diamond fitting.

The new adapter plate seems like it will work well, though.
Until I see a reason to use a liquid gasket, I'd rather stick with the OEM style design. It just seems much more "refined" to me. Maybe I just don't like gluing parts onto my car, LOL. In the end it probably is a better seal, I just am not a fan. Sorry if you think this post is a complete waste of time, I just think it's good to have the information out there (and not require searching another forum to find it).
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Old 03-08-2011, 09:55 PM   #17
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Updated the first post with the new product photos from RallySportDirect.

EDIT: I found that RallySportDirect already has the new valve on their site. Here is a photo of the one I have.



EDIT: I found that RallySportDirect already has the new valve on their site. Here is a photo of the one I have.



You can see the groove for the OEM diamond shaped gasket to fit into. Make sure you don't damage this or you'll have to buy a new one from the dealer. The Forge valve does not come with this seal. You can see from this photo that the bottom of the piston looks the same, but the hole for the air to act on the piston is much larger than on my old valve. This allows for a greater surface area for the pressure to act upon. Area x Pressure = Force, so assuming the same boost pressure, there is now more force trying to open the valve. This results in quicker response!
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Old 03-08-2011, 10:26 PM   #18
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cool. Just make sure you call your new invention "the wheel". I don't think that one is taken yet.
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Old 03-08-2011, 10:28 PM   #19
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Quote:
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cool. Just make sure you call your new invention "the wheel". I don't think that one is taken yet.
You're mad because there is a new part, or because you think this post is a waste of your time?
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Old 03-08-2011, 10:46 PM   #20
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Oh, not mad at all man.
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Old 03-08-2011, 10:52 PM   #21
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Just trying to help someone avoid buying the "wrong" part like I did. I don't see why this turned downhill so fast.

Do you have an intake on your car? Do you get any "flutter" on low boost shifts? I'm wondering if that is a common occurrence with the Mazda valve on a Subaru or it is was just my car.
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Old 03-08-2011, 11:03 PM   #22
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yeah I get flutter. Ive had flutter with the stock valve, a GFB hybrid valve, a HKS SSQV valve, a Greddy valve and a forge.

The flutter can be caused by a 3port ebcs or the bpv/bov. Its really not a problem.

If you get flutter at low boost shifts, dont worry about it. You arent hurting anything. When you start getting loud flutter at high boost, thats compressor surge. At vac or low boost shifts, your compressor isnt surging.

When picking springs, pick the lightest spring you can and have the valve stay closed at idle vac levels. If you find it is in between two springs, pick the lighter of the two, and start to shim it. You can use washers from the hardware store to shim a forge valve. Add one at a time to increase a spring's stiffness, up to 3-5 washers (depending on thickness..doesnt matter as long as valve can fully open), and see if that gets the valve to hold closed at idle vacuum. Run the lightest spring and the fewest washers you can.

The purpose of spring tension isnt to fight against boost pressure. Its to fight against vacuum. the valve should open quickly, but fully seat closed at idle vacuum. When you have that, its tuned right. Subaru's pull a lot of vacuum, so you need a little bit of spring tension.
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Old 03-09-2011, 08:04 AM   #23
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Quote:
Originally Posted by KurtP View Post
yeah I get flutter. Ive had flutter with the stock valve, a GFB hybrid valve, a HKS SSQV valve, a Greddy valve and a forge.

The flutter can be caused by a 3port ebcs or the bpv/bov. Its really not a problem.

If you get flutter at low boost shifts, dont worry about it. You arent hurting anything. When you start getting loud flutter at high boost, thats compressor surge. At vac or low boost shifts, your compressor isnt surging.

When picking springs, pick the lightest spring you can and have the valve stay closed at idle vac levels. If you find it is in between two springs, pick the lighter of the two, and start to shim it. You can use washers from the hardware store to shim a forge valve. Add one at a time to increase a spring's stiffness, up to 3-5 washers (depending on thickness..doesnt matter as long as valve can fully open), and see if that gets the valve to hold closed at idle vacuum. Run the lightest spring and the fewest washers you can.

The purpose of spring tension isnt to fight against boost pressure. Its to fight against vacuum. the valve should open quickly, but fully seat closed at idle vacuum. When you have that, its tuned right. Subaru's pull a lot of vacuum, so you need a little bit of spring tension.
Or...

Once again, and because it was my BPV/BOV solution on my 05 LGT and works perfectly on my 11 WRX, I remind readers there is another, cheaper, stock-looking solution:

http://forums.nasioc.com/forums/showthread.php?t=454965
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Old 03-09-2011, 10:45 AM   #24
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Or...

Once again, and because it was my BPV/BOV solution on my 05 LGT and works perfectly on my 11 WRX, I remind readers there is another, cheaper, stock-looking solution:

http://forums.nasioc.com/forums/showthread.php?t=454965
Thanks for the link. It is an interesting read, and I can definitely see that working for many people. What it does, is essentially make the stock BPV operate just like the Forge valve, but it only costs a few cents. Here are a couple other links I found as I went through that thread. It looks like DSM's use a nearly identical stock BPV and have been doing this for quite a long time as well. These links do a bit better job of explaining what's actually going on (without reading that entire thread).

http://www.dsmtuners.com/forums/arti...-101-mods.html
http://www.thedodgegarage.com/turbo_bov_mod.html

This is a really good diagram that shows how the stock BPV works:

http://members.inode.at/r.kovac//subee/BOV_mod.JPG

I couldn't find an un-edited version, but if you ignore the colored stuff you can see that the vent hole will result in equal pressure on both sides of the diaphragm while under boost. This creates a pressure balance, so the only thing holding the valve shut is the spring. The strength of the spring directly dictates how much boost you can hold. The spring is installed from the factory with enough force to hold the valve closed at stock boost levels, with a little bit of headroom. That's why they leak when you go much past stock boost.

When you do the mod to block off this hole (and drill a vent out the side to keep the bottom of the diaphragm at atmospheric pressure), you are essentially creating a valve that should never leak. Under boost you have spring pressure and boost pressure pushing down (and the boost pressure pushing down on the diaphragm has a large area to act upon). The only force pushing upwards is boost pressure on the bottom of the piston (smaller area than the top of the diaphragm). These pressures should always be equal, but the net force will always be downwards (due to the spring, and the differential area). Essentially, the more boost you are running, the more tightly the valve will seal. This is how most all piston style BPV/BOV's are set up (including the Forge).

This is great. For just a few pennies you get a valve that should never leak, no matter how much boost you throw at it. The only "problem" (in my mind) is the lack of adjustment. With the modded design, the spring only needs to be strong enough to hold the valve closed at vacuum, it has nothing to do with boost holding ability. Due to the OEM design, the spring that is in the valve is very heavy. With a heavy spring you sacrifice response. That is why a lot of people in that thread noted a slight to moderate amount of flutter on low load shifts. Alternatively, it could be argued that the heavy spring is good, because it limits pressure drop during shifting, but that is mostly user preference.

So, IMO, the mod is really a good one. It essentially transforms your stock part into the same thing as a $150-250 part. The only downside is lack of adjustability. With an aftermarket valve you can choose the spring/shim combo to exactly what you want. If you happen to want a really heavy spring / slow valve response, then it's a no-brainer to just do the mod. If you want the lightest possible spring, and the quickest pressure release, then I you have to shell out the $$$ and buy an aftermarket unit.
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Old 03-09-2011, 11:45 AM   #25
SeeeeeYa
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That's an excellent synopsis, xluben.

The "problem" you envision because of lack of adjustment was a concern of mine as well. In practice, however, such "flutter" is minimal and has led to me becoming smarter with my accelerator. That is, knowing what it is, I do not accelerate unnecessarily then have to let off quickly.

Also, having run this modded stock BPV my LGT for many years and now my WRX, I have personally defined the so-called flutter as something other than compressor related...((EDITED; it IS compressor surge, in fact )) it is the BPV itself and a non-issue AFAIC. It even has value, as I mentioned, as feedback on the conditions in the engine's intake system. (Of lesser but admitted value, it makes a wicked nice release sound now, different and sharper than stock.)

My LGT needed a better BPV because of mods. It was a 5EAT and its IPT's shifting was spectacular. My WRX is a 5MT and shifting depends on me... and in my mind the stock BPV was poorly suited for any kind of spirited shifting, so I turned to the $0.16 mod once again. I figured it would provide a more seamless power stream during shifting due to retention of, some, boost during shifts.

It does that, curing a dissatisfaction with my shifting performance, and giving the car an overall more muscularly taut feel.

For most, that Forge you highlighted is an excellent option, obviously providing the same benefits as I see with this modded stock unit... mine's just "done today with no money."

I will note two slight changes I made to the original mod specs (note that it was on a metal BPV and the LGT and 08+ WRX are plastic, also) to address my own thoughts:

1) I drilled a very small 1/16" hole down close to the flange in that vent-boss, about 1/4" above the flange. I did this to provide a timed dampening to the opening of the valve... again to aid in the shift transitions. The valve cannot be snapped open simply because it has to suck air through that little orifice, as opposed to the 7/16" or so hole it normally would see.

2) I covered that hole with a section of felt, secured with RTV, as a filter.

Last edited by SeeeeeYa; 01-01-2013 at 07:08 PM.
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