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sashadg1 12-09-2012 01:51 PM

Best way to adjust GFB BOV
It does not seem to matter whether I blow out full atmosphere or fully recirc. It does not backfire or have rough idle. There is also the center adjustment that is responsible for how easy the air is released and how long the valve stays open for.

If I set for 50% Blow off to atmosphere w/ no back fire will that still be okay? I know there is a second that the MAF does not get the air it accounts for causing a rich condition. Can it cause other issues other than backfire?

I simply installed the new BOV and made no adjustments. I sure adjustments need to be made but what are they and what is the best place to start from?

Any advice would be great.

Thank you,


charlie_sheen 12-09-2012 01:56 PM

if youre stock turbo you should be fine right out of the box. i had to mess with my spring a little, and i keep mine at about 40 % atmosphere 60 % recirc. i was always adjusting mine trying to get rid of the wimpy fart sound before the "pshhh" but it never went away until i went to a FMIC

Drift Motion 12-09-2012 01:59 PM

You should probably state if you have the GT hybrid or Respons (sp?)

ericem 12-09-2012 05:11 PM

With the GFB if you are fully open it is actually 50/50 not 100% atmosphere. Look at the valve with it out of the car you will notice both ports are open.

sashadg1 12-09-2012 06:30 PM

To late now it is installed and I am not taking it off to confirm :) According to the instruction sheet that is not the case in regards to fully open open only being 50% but maybe you are on to something.
Also I thought this BOV would put out a high pitched whistle and whoooossshhh sound. This is just a sloppy sounding whooosshhh. Is that a different brand that sounds like this? Not a big deal though. I am almost certain I was leaking under boost as the boost it much more constant and power is up. I do not have a boost gauge just yet believe it or not.

sashadg1 12-09-2012 06:41 PM

Sorry this is the GFB Respons TMS, T9001. Also I have the standard trumpet so whooossshhh is all I get unless I buy the long trumpet.
Still need to understand how I should adjust the center spring for pressure control and length of time it releases.

iNVAR 12-10-2012 06:45 AM

If the screw is too loose, there won't be enough pressure on the spring, and ergo the piston will move too easily and may move or remain open during idle. You do not want that.

If it's too tight, then you'll hear flutter from compressor surge during vent conditions because the piston doesn't open quickly or wide enough.

The way I did it was I tightened it down a turn and made sure the idle was good and it wasn't venting. You can actually see the piston through the VTA port. If it's closed, tighten the spring down another 1/2 to 1 turn and drive the car and see if it vents okay under boost (WOT and partial). If it's okay, tighten it down a bit more and check again. Repeat until you just start to hear the flutter, then back the spring off a half turn or so and you should be fine.

edit: Sorry, just reread my post and want to clarify: look through the VTA port. If the piston is moving at idle or open, tighten it down gradually until it closes, and then tighten it just another half a turn more. THEN drive off and see if it vents properly. No compressor surge means you can tighten it down a tiny bit more. When you get just the tiniest bit of surge, back the spring off a bit.

sashadg1 12-10-2012 03:00 PM

Cool thanks that makes total sense.


iNVAR 12-10-2012 03:26 PM

edited my post a bit to clarify.

Strizzy 12-10-2012 04:52 PM

m sprank 12-10-2012 05:29 PM

^ Thank you sir.

Funny thing, OP is a customer of mine, but did not buy the BOV from me. It was accidentally shipped from another vendor to my shop and I forwarded it to the OP.

Scott, it cost $10 and change to ship it to you. lol.

tDoug60 12-11-2012 08:54 PM

Jw would a bov fr a08+ wrx work on our cars?

Drift Motion 12-11-2012 11:08 PM

yes, same TMIC/flange

sashadg1 12-12-2012 01:04 AM

Hey Mike,

I did not even thing about that, I will get you back on that. Thanks for the quick ship.


m sprank 12-12-2012 01:07 PM

No problem. Have fun with the GFB. My favorite BOV/BPV for a Subie.

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