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-   -   $0.16 BOV mod on NASIOC (http://legacygt.com/forums/showthread.php?t=197583)

mitskip 12-06-2012 01:04 PM

$0.16 BOV mod on NASIOC
 
I have had a hard time finding any helpful threads on this forum about this mod. I read through most of the pages of this thread on NASIOC:
http://forums.nasioc.com/forums/showthread.php?t=454965

I am just curious to see how many of us have tried this w/ success on the stock BPV. My tuner has told me that due to the elevation in SLC stock BPV only holds about 15-16 lbs of boost. Just wanting to hear opinions on this and more people that have had experience with this on an LGT.

Thanks!

Nrw 12-06-2012 01:20 PM

Stock plastic BPV's suck no matter the elevation. Buy a forge /thread

.:Catalyst:. 12-06-2012 03:15 PM

^ :cool: ^

f1anatic 12-06-2012 09:52 PM

So you take advice from a forum dedicated to a different car and more importantly a different engine (2.0) and different parts (BOV) and expect to achieve safe results? Go ahead. The thread you referenced is 10 years old...

technicalgarage 12-07-2012 01:18 AM

This mod applies to any bpv of recirculating design that has a lower boost reference hole in addition to the boost/vac hose on top. That means it will work on the lgt.
There's even a company that does this in Japan and sells the modified valves at ripoff prices: http://www.coto-sports.com.

Anyway, I did this a couple of years ago, both on my oem bpv, and my dsm 1g bpv (metal!) that I modded to fit the lgt flange.
You'll likely see some mild compressor surge on moderate throttle shifts which isn't harmful, but it won't do a damn thing performance wise.
Theoretically your bpv will close faster on boost and keep it shut even at higher boost levels with the mod, but higher boost levels seem to play nice with the lgt bov.
In summary, not worth the time or effort unless you're bored and have nothing to do.

SeeeeeYa 12-07-2012 10:16 AM

I did this on my 05 LGT. I had to retune slightly after the AVO380 because it was apparently leaking pre-mod. I credit its modified capacity to my 5EAT LGT's power through the gears

I did this on my 11 WRX. Why not, it provides every positive attribute of a Forge, but for virtually free. Plus, it has the reliability of an OEM part. This one was plastic like the LGT's BPV. The addition to the WRX's driving performance was immediately obvious.

I did this to my 11 STi. Better, all metal construction, but basically the same BPV. Better, bigger, vent orifice... for the bigger TMIC, I guess. Same process to modify. Same welcomed addition to driving/power performance. Even gave it a twist of my own.

Anyone who has read the complete mod thread "over there" will come across my posts. I've been vocal about the virtues of this mod for years on here as well as other forums. It provides virtually the same BPV as was OEM on JDM STi at one time, at FAR less cost than importing one. Lots of years, three different turboed Subarus, all without an issue, all while addressing once and for all every issue related to a BPV/BOV.

mitskip 12-07-2012 10:26 AM

Thanks Technicalgarage. So, you're saying this wont allow my BPV to hold more boost?

mitskip 12-07-2012 10:29 AM

SeeeeYa, I will read through the thread again. I figure why not give it a try if its not going to hurt anything and it holds more boost, saves me the money over getting a Forge.

mwiener2 12-07-2012 10:45 AM

If your BOV is leaking, it's broken or you've got it hooked up wrong.

BOV's not being able to hold boost above xx is complete BS. By design, they don't care what the boost pressure is. They always have the same spring pressure holding it closed.

GTTuner 12-07-2012 11:20 AM

Hmmmm. Interesting.

unclemat 10-16-2013 01:55 AM

Quote:

Originally Posted by mwiener2 (Post 4191140)
If your BOV is leaking, it's broken or you've got it hooked up wrong.

BOV's not being able to hold boost above xx is complete BS. By design, they don't care what the boost pressure is. They always have the same spring pressure holding it closed.

Read the nasioc thread before you come out with one of your usual dumb generalizations :spin:

It's obviously false with the stock design BPV. Under boost, the stock has positive manifold pressure applied to all:

the bottom of the valve, AND
the bottom of the diaphragm, AND
the top of the diaphragm.

Yes, there are two "ands". There is this extra hole next to the valve that supplies pressure to the bottom of the diaphragm (so the bottom of the diaphragm gets pre-throttle body air, while the top gets post-throttle body air).

Technically at boost, the pressure on both sides of the diaphragm is equal, so all that is counteracting the pressure applied on the valve is the spring force. Given high enough boost the spring force will be overcome.

If by design stock BPV was capable of holding any amount of boost, people could use it with GT35Rs... Well, they can with the "$0.16 mod".

mwiener2 10-16-2013 04:55 PM

I'm using my stock bpv at 28psi on my car.

laff79 10-16-2013 04:57 PM

Wow

mwiener2 10-16-2013 04:58 PM

Quote:

Originally Posted by unclemat (Post 4611718)
Technically at boost, the pressure on both sides of the diaphragm is equal, so all that is counteracting the pressure applied on the valve is the spring force. Given high enough boost the spring force will be overcome.


Your first sentence is opposed to your second sentence. If boost is equal on both sides of the diaphragm, then the only thing holding it closed is the spring pressure. If boost is equal on both sides, then it doesn't matter what the boost level is because the spring is always holding it closed.


The reason you don't see big turbo cars with stock BPV's is marketing and bling. My car only has a GT30r not a 35 so I guess that's why I can get away with the stock bpv.


edit: After re-looking at the nabisco thread... the OP of that thread doesn't even know what boost level he is at because his gauge max's out at 20psi. That's some quality tuning there.

unclemat 10-16-2013 05:57 PM

Quote:

Originally Posted by mwiener2 (Post 4612352)
Your first sentence is opposed to your second sentence. If boost is equal on both sides of the diaphragm, then the only thing holding it closed is the spring pressure. If boost is equal on both sides, then it doesn't matter what the boost level is because the spring is always holding it closed.

You still don't get it.

It's not just diaphragm. There is also pressure applied to BOTTOM of the valve. Given high enough boost the valve will open.

http://i49.tinypic.com/281a0p3.jpg


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