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Old 11-17-2003, 08:42 AM   #1
TheMadScientist
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Default $0.16 BOV mod

OK so I am a cheap sob. I want to run over 18psi on my 16G but the stock BOV opens around that pressure. So what are my options?
1)Buy an atomsphere BOV.
I borrowed one and got really sick of the noise I like stealth.
2)Buy a recirculate BOV.
I am cheap and don't want to spend $200+ on one.
3)The $0.16 mod
Very cheap and stealth this fit the bill perfect. Still 100% recirculate so no idle problems or rich between shift problems. This will allow you to run as much boost as you can throw at it and not open. The one drawback to this that I have found is that around 5-10psi when you shift you will get a real quick real short surge. This will not happen at higher boost levels.

The Mod:
Take off the BOV and look at the face that mounts to the IC. You will see two holes a big one and a small one. The big hole is the valve that releases the pressure the small hole is a boost signal line.
What I did was to take a 1/4-20 tap and drilled out the small hole and tapped it. Be careful to not let any shavings go into the hole. I held the BOV upsid down while drilling and tapping. Then I took a 1/4-20 set screw put teflon tape on it and sealed off that hole.
Then on the body of the BOV you can see where that signal hole goes through the casting. You want to drill in to that signal line and vent it to atmosphere. There is a bung cast into the BOV body to do this.

I have some pics that I will try to post tonight. Any comment or questions?

Mark
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Old 11-17-2003, 09:01 AM   #2
busky2k
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So how does it feel after you've done the mod? Holds boost better?
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Old 11-17-2003, 09:33 AM   #3
Rickyh
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Could you just crush the cap a little? I have heard of people doing this on dsm's to get them to hold more boost?
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Old 11-17-2003, 09:55 AM   #4
TheMadScientist
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Quote:
Originally posted by busky2k
So how does it feel after you've done the mod? Holds boost better?
There is nothing that I can feel that is different. Except that the BOV now holds a rock solid 20psi. I am sure that it will hold more but my boost gauge only reads to 20psi.
Crushing the top would probably work too. But eventualy you will run into the same problem at higher boost. From what I can see (I cut open another stock BOV) The more boost you run the tighter the BOV will close with this mod.
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. 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.
Hope that makes some sense.
Mark
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Old 05-23-2005, 07:08 AM   #5
brenden3010
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Quote:
Originally Posted by TheMadScientist
There is nothing that I can feel that is different. Except that the BOV now holds a rock solid 20psi. I am sure that it will hold more but my boost gauge only reads to 20psi.


So you could be holding 29389283 psi, but you have no clue, right? You only know its over 20... watch out.
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Old 05-23-2005, 08:39 AM   #6
pezman04wrx
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^^^ I'd venture a guess that he's running a better boost gauge now since the post you mentioned is from 03', and it was on a totally different car ...
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Old 05-23-2005, 09:11 AM   #7
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Quote:
Originally Posted by brenden3010
So you could be holding 29389283 psi, but you have no clue, right? You only know its over 20... watch out.
I set the WRX up using the Utec boost #'s from log1. Set to 22-23psi.


Quote:
Originally Posted by pezman04wrx
^^^ I'd venture a guess that he's running a better boost gauge now since the post you mentioned is from 03', and it was on a totally different car ...
Well the same boost gauge is on the Sti now. But I have the boost set to stock right now.

TMS
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Old 05-24-2005, 01:09 AM   #8
Athena
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Air Power Systems Pty Ltd has this to say about their blow off valve:

APS BOV development:

We are often asked why we developed our own blow off valve when there are so many on the market. Quite frankly APS had not found a blow off valve for the WRX/STI that offered the level of performance required.
With a large turbocharger, releasing pressure from the turbine compressor wheel when the throttle is snapped shut is critical not only for turbocharger response, but for turbocharger longevity. A huge volume of air must be passed through the blow off valve as soon as the throttle is closed.

Most blow off valves have limitations in their design that inhibit the level of performance we demand. Piston/bore diameter and venting ports are often too small and surprisingly, most will not fully expose the exhaust ports when fully opened.

Ultimately, the need for a truly high performance blow off valve specifically designed for the WRX/STI needed to be satisfied.
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Old 11-04-2007, 02:26 PM   #9
BurschiK
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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 11-11-2007, 12:28 PM   #10
BurschiK
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Quote:
Originally Posted by BurschiK View Post
First of all, please excuse my bad english, I'm coming from Austria
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
Ok ok, my fault was to think that the hole goes to the backside of the diaphragm
I did this mod now too, but I wasn't happy with the hole getting unfiltered air into the BOV. So I did the Mod this way:

I love that PFZISCHHHHH at shifting
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Old 11-17-2003, 10:20 AM   #11
Wheeler Bement
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does it still dump the boost as fast as it should between shifts?
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Old 11-17-2003, 11:57 AM   #12
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Quote:
Originally posted by Wheeler Bement
does it still dump the boost as fast as it should between shifts?
Depends on how much boost. At lowwer boost levels 5-10psi I get a very very brief surge less than 1/2sec then vents normally. It is fine at higher boost levels 15-20psi. So far ther are no driveabilty issues.

Mark
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Old 11-17-2003, 12:44 PM   #13
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You can always buy an STi BOV for under $100. My engine is putting out over 20 psi and never had a problem with the stock STi BOV. I might even sell mine, I'm still trying to decide between keeping the TXS RFL or keeping the JDM STi BOV. Actually, I might just sell them both. Let me know if you'd be interested, definately cheaper than an aftermarket one.
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Old 11-17-2003, 04:08 PM   #14
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I crushed my stock BOV, old DSM thing.. sounds alittle simpler than what you did.
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Old 04-25-2008, 11:53 AM   #15
newbluwrx
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Quote:
Originally Posted by PaulRex View Post
I crushed my stock BOV, old DSM thing.. sounds alittle simpler than what you did.
how did you crush it? im lookin to do the same to mine but no sure exactly how to
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Old 11-17-2003, 04:12 PM   #16
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Quote:
Originally posted by garface
You can always buy an STi BOV for under $100. My engine is putting out over 20 psi and never had a problem with the stock STi BOV. I might even sell mine, I'm still trying to decide between keeping the TXS RFL or keeping the JDM STi BOV. Actually, I might just sell them both. Let me know if you'd be interested, definately cheaper than an aftermarket one.
Arn't the STI BOV springs less stiff than regular usdm wrx bov springs? that is what rallispec reported when they tested a V7 sti BOV vs. a MY02 usdm bov. They said it was actually less stiff maybe to react quicker.
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Old 11-17-2003, 06:47 PM   #17
Schleppy
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You're the mad scientist Mark
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Old 11-17-2003, 07:20 PM   #18
Greg Sharpe
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Yeah, the STi recirc BOV has a softer spring and is lacking the boost signal port. The divit for the port is there, but it isn't drilled all the way through.
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Old 11-17-2003, 07:27 PM   #19
TheMadScientist
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So this mod changes the WRX BOV into an STi BOV but with a harder spring?
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Old 11-17-2003, 09:05 PM   #20
TheMadScientist
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Talking

Here are the pics.
Attached Images
File Type: jpg block this hole.jpg (23.0 KB, 7874 views)
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Old 11-17-2003, 09:06 PM   #21
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I have more but these two should do.
Attached Images
File Type: jpg drill this hole.jpg (25.6 KB, 7492 views)
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Old 11-24-2003, 03:07 PM   #22
Davenow
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I am going to do this very soon...
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Old 11-24-2003, 06:57 PM   #23
n2xlr8n
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I wacked mine with a small ball-peen....good to 24 psi @ 7200 so far.
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Old 12-06-2004, 06:02 PM   #24
rewt
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Quote:
Originally Posted by n2xlr8n
I wacked mine with a small ball-peen....good to 24 psi @ 7200 so far.
i don't mean to hijack the $0.16 mod, but where did you hit the BPV with the hammer? also, how hard did you hit it? i think i would rather use a hammer than drill and tap.
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Old 04-26-2005, 01:18 AM   #25
sam caldwell
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Quote:
Originally Posted by n2xlr8n
I wacked mine with a small ball-peen....good to 24 psi @ 7200 so far.
you and your hammer stay away from my car please
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