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Old 05-06-2007, 06:25 PM   #151
JaMes W
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I disagree. I have tried 5 different bov's , 100% atmosphere and fully adjustable. tried them all at the track. Guess which one im using now?

With 100% atmosphere bov the rpm's drop significantly between shifts and when revving . With a recirculating valve the rpm's stay up higher longer. This keeps your rpms closer to where they should be when going into the next gear.


Quote:
Originally Posted by WRX_UA View Post
I have been running Blitz Dual Drive BOV for a year already. Its atmospheric BOV. Tried to use stock one with NO mods (because I didn't know) DUMPED TO ATMOSPHERE... It occured to be to soft and I had MAJOR idle problems like jumping from 500 to 1600rpm continiously and then the engine stopped completely... . Now, read this thread. Blocked the hole, drilled the new hole, as on the picture shown. Tomorrow i will install and make a write-up about the modded stock WRX BPV. BUT(!) mine will be ATMOSPHERIC, without recirculation, because recirculated BPV DO NOT keep up with FAST SHIFTING. The car jerks, between fast shifts.
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Old 05-06-2007, 06:55 PM   #152
tube
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.16 mod = surge.

I did this mod and it was utter garbage, my turbo surged under every possible boost level.

I blocked the hole I drilled and removed the set screw, no surge, perfect.
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Old 05-07-2007, 04:07 AM   #153
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Quote:
Originally Posted by JaMes W View Post
I disagree. I have tried 5 different bov's , 100% atmosphere and fully adjustable. tried them all at the track. Guess which one im using now?

With 100% atmosphere bov the rpm's drop significantly between shifts and when revving . With a recirculating valve the rpm's stay up higher longer. This keeps your rpms closer to where they should be when going into the next gear.
And what about pure acceleration with ultra-fast shifts??
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Old 05-07-2007, 09:26 AM   #154
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Quote:
Originally Posted by WRX_UA View Post
I have been running Blitz Dual Drive BOV for a year already. Its atmospheric BOV. Tried to use stock one with NO mods (because I didn't know) DUMPED TO ATMOSPHERE... It occured to be to soft and I had MAJOR idle problems like jumping from 500 to 1600rpm continiously and then the engine stopped completely... . Now, read this thread. Blocked the hole, drilled the new hole, as on the picture shown. Tomorrow i will install and make a write-up about the modded stock WRX BPV. BUT(!) mine will be ATMOSPHERIC, without recirculation, because recirculated BPV DO NOT keep up with FAST SHIFTING. The car jerks, between fast shifts.
Oh boy. Not sure where to start and how to answer this post. I guess I'll go from the begining.

You had idle issues because you had a vacumm leak if your recirculating hose was not connected. The BPV opens at idle and that spells all kinds of trouble if you're venting to atmosphere. Not sure if modded BPV will herlp you unless it stays shut during idle.

Why do you think the recirc valve does not keep up? I am not even sure what that means. Are you comparing the behavior to your BOV? How is the BPV supposed to keep up? It has to open when you close the TB plate in order to prevent compressor surge. If your BOV stays closed longer, it will cause compressor surge which isn't a good thing for your turbo. It's very bad for performance too since it will take more energy now to get the turbine spinning again since it's probably rotating in the other direction now.

I hope you also understand the implications of venting to atmopshere. You're venting metered air which will throw off your fueling significantly, especially at high boost situations. Running rich is one thing. Another, which most people don't realize, is that you actually loose power if you're venting to atmosphere. Basically, making power is all about how much oxygen you can pump into the motor. By venting out, you're actually removing air from the intake. Less air equals less power.

There are really good reasons why you shouldn't be running a BOV. Modded stock BPV recirculating to atmosphere will probably not help your 'fast shifting' issues. Honestly, if you don't want jerking, get the rev matching right.
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Old 05-07-2007, 05:08 PM   #155
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Quote:
Originally Posted by Ziggyrama View Post
Oh boy. Not sure where to start and how to answer this post. I guess I'll go from the begining.

You had idle issues because you had a vacumm leak if your recirculating hose was not connected. The BPV opens at idle and that spells all kinds of trouble if you're venting to atmosphere. Not sure if modded BPV will herlp you unless it stays shut during idle.

Why do you think the recirc valve does not keep up? I am not even sure what that means. Are you comparing the behavior to your BOV? How is the BPV supposed to keep up? It has to open when you close the TB plate in order to prevent compressor surge. If your BOV stays closed longer, it will cause compressor surge which isn't a good thing for your turbo. It's very bad for performance too since it will take more energy now to get the turbine spinning again since it's probably rotating in the other direction now.

I hope you also understand the implications of venting to atmopshere. You're venting metered air which will throw off your fueling significantly, especially at high boost situations. Running rich is one thing. Another, which most people don't realize, is that you actually loose power if you're venting to atmosphere. Basically, making power is all about how much oxygen you can pump into the motor. By venting out, you're actually removing air from the intake. Less air equals less power.

There are really good reasons why you shouldn't be running a BOV. Modded stock BPV recirculating to atmosphere will probably not help your 'fast shifting' issues. Honestly, if you don't want jerking, get the rev matching right.

I dont agree with you. I'm not the only person that have such issues with very fast shifting. When you go full throttle and shift next gear in .5 sec or less BOV (atmo) discharge the air from intercooler (compressor is spinning very fast with no surge with BOV and immedeately sucks new air to continue the flow in next gear) and in this case BPV creates an additional, unneeded air in intake system which ruins the whole scene. I TOTALLY AGREE that BPV is more efficient in daily driving, partial throttle, but in pure racing - NEVER! BOV may create a lot of back firing when cruising around town as a main problem - everything else is positive.

Also tried 0.16 mod - CRAP, BOV appeared to be too stiff.
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Old 05-07-2007, 10:17 PM   #156
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Quote:
Originally Posted by WRX_UA View Post
in this case BPV creates an additional, unneeded air in intake system which ruins the whole scene.
That is where you lose me. Somehow air in the intake is bad?
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Old 05-08-2007, 05:47 AM   #157
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^^^ Indeed. I also do not understand why that is bad. WRX_UA, it's really not 'additional' air. It's air you already metered, not some extra stuff you picked up. In order for your fueling to stay right, it has to be recirculated. How does that ruin your scene? How does air in the intake make you jerk the car? If you can convince me with a good explanation, I'd really appreciate it.

If you don't get this jerking with a BOV, it's due to other factors that the BOV induces that are just side effects of its operation, not the actual function of the BOV. It most likely induces an overly rich condition during the shift which may cover up a poorly programmed open/closed loop transition in your setup that gives you that jerk. Rich fueling tends to feel very mellow and smooth do the driver so a bad transition would feel better with some enrichment. Just speculating here but it sounds like a very likely scenario.

Also, don't say that it must be true because lots of other people are seeing the same thing If you are arguing a technical aspect, you need to bring some technical info into the table. It's really hard to gain credibility otherwise. What you're arguing makes no sense. So, convince us otherwise with some good, concrete explanation.
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Old 05-08-2007, 11:50 AM   #158
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One of the reasons I ditched the modded BPV is that it was slow to close after a fast shift. It felt like I had just ran into a wall.
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Old 05-09-2007, 02:51 PM   #159
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Quote:
Originally Posted by x99percent View Post
One of the reasons I ditched the modded BPV is that it was slow to close after a fast shift. It felt like I had just ran into a wall.
YES!!! You're absolutely right!!! I have terrible jerking and "hitting the wall" after almost every shift... This is may be the result of that portion of air injected back to intake system. Too much air appears in the intake system.(this are just thoughts). All I know that with Atmo BOV, the car strikes after every fast-shift... with BPV it jerks. AND THIS IS OPINION OF EVERY SUBARU OWNER I KNOW except nasioc.com members.
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Old 05-09-2007, 02:59 PM   #160
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I'll eat some humble pie. Going to do the mod, as mine won't hold pressure anymore. Oh well, I guess this time I actually read this thread.

Last edited by paintbing; 04-05-2008 at 12:18 AM.
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Old 05-09-2007, 09:51 PM   #161
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Quote:
Originally Posted by paintbing View Post
This mod is garbage. Ever wonder why this mod isn't stickied anywhere?!? Let this thread die. PLEASE!

Hahahahahahahaahhaha i was sold on this mod till i saw your post lol

This is awesom guys

So whats the deal fellas............ do it or not?
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Old 05-09-2007, 10:34 PM   #162
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If you like your turbo, don't do it.

I did it and almost ruined my BPV. Good thing I was able to plug the hole I drilled with the same set screw that I used to plug the other hole.
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Old 05-18-2007, 04:05 PM   #163
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I did this on my 18g setup and it works great. Holds 21psi perfectly fine, and sounds decent too.

Also never had any problems with surge; however, I welded the hole up instead of putting a screw in, maybe that's got something to do with it???

my .02
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Old 05-18-2007, 04:40 PM   #164
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It did ruin mine.

I would randomly lose boost with it on occasions, sometimes it wouldn't open.

Surges, shifting is sticky.

I am lucky a local guy gave me one for free.
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Old 05-19-2007, 08:28 PM   #165
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any more who have tried this wanna chime in?
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Old 09-03-2007, 02:15 AM   #166
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Ninja edit

Last edited by Wrx_Fan_0717; 11-18-2007 at 05:13 PM.
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Old 09-03-2007, 06:37 AM   #167
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i can't believe some people believe this mod doesn't work.



i've never looked back since the day i did it on 8/16/2004. as of today, that's 1119 days.

i drive my car every day. it's worked perfectly every time i drive my car.

the only reason to do this mod is if you want a relatively tightly sprung, oem-quality, zero-maintenance, infinite boost capable, recirculating bpv for basically zero investment. if you don't want that, move on.
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Old 09-03-2007, 09:04 AM   #168
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Thats why a rap with a ballpien hammer is better and cheaper than $0.16

I modded mine over 3 years ago, no problems until I needed to hit 28psi.

Jay-R

Quote:
Originally Posted by Wrx_Fan_0717 View Post
Late but for another response. Just put a modded BPV on and surges to all hell. Unless at full throttle high rpm shift. Still flutters a little. I don't know maybe im an unlucky one?
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Old 09-03-2007, 12:33 PM   #169
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Quote:
Originally Posted by ride5000 View Post
i can't believe some people believe this mod doesn't work.



i've never looked back since the day i did it on 8/16/2004. as of today, that's 1119 days.

i drive my car every day. it's worked perfectly every time i drive my car.

the only reason to do this mod is if you want a relatively tightly sprung, oem-quality, zero-maintenance, infinite boost capable, recirculating bpv for basically zero investment. if you don't want that, move on.

Do you have your silencer on? You running a stock intake? You probably just cant here it.
Cause my surges bad. I'll make a video. I would suggest taking it off and swapping for a smashed stocker.
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Old 09-03-2007, 01:22 PM   #170
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I modded mine with epoxy and it holds to 25 psi perfectly... no problems here
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Old 09-03-2007, 08:05 PM   #171
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Quote:
Originally Posted by Wrx_Fan_0717 View Post
Do you have your silencer on? You running a stock intake? You probably just cant here it.
Cause my surges bad. I'll make a video. I would suggest taking it off and swapping for a smashed stocker.
dude, i know what surge sounds like. some of us have been playing around with subies for quite some time now.

a little waffle is perfectly fine with me. are you going to tell me that my vf23 is going to die any second now? when it does, can you tell me it was the modded oem bpv, or the fact that i flog 25psi out of it every day? how about the period of time last winter when i was running 27+psi?

crushing the top postpones the inevitable. if you understand the way the bpv is put together, and how it operates, you would know this. this is exactly why dibble only got his up to 28psi. i GUARANTEE you that mine will hold that, and more. i know because i've done it.

ken

ps. since you think surge of any kind is the devil, why don't you tell quirt he's an idiot for selling garrett gt series turbo kits WITHOUT any kind of bpv/bov?
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Old 09-03-2007, 09:03 PM   #172
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I ran 25 psi on my pe1820 clone (1.5 years) and 27 on my 20g ( .5 years) with this mod and never had any issues. I wish i still had the modded stock bov with the rotated set up. I am sure it would have held fine.
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Old 11-04-2007, 01:26 PM   #173
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Question

First of all, please excuse my bad english, I'm coming from Austria
Quote:
Originally Posted by TheMadScientist View Post
There is a diaphram inside the BOV before this mod the pasage that you block allows boost to be equal on both sides of the diaphram and relies on the spring to hold it closed.
So far so clear
Quote:
After the mod you have boost and the spring pushing the BOV closed with atmosphere trying to push the valve open so the more boost you run the tighter the valve closes.
Mark
This is what I don't unterstand. After your mod you have the boost pushing against the valve, on the other side of the valve you have atmospheric pressure plus the spring load
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Old 11-04-2007, 01:42 PM   #174
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Old 11-04-2007, 04:25 PM   #175
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subarus stock bov is good for 25 psi I tested it myself
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