Jump to content
Please check your junk folder for registration emails ×

Removing secondary relief bov Twin Turbo?


Recommended Posts

It is possible to close over (plug) the secondary relief valve? If got a GFB response on 50/50 but its quiet (cant hear it at all!) and was wondering if removing that would make it louder

Also what size silicone line do i need for vac lines ect. Want to change original lines for silicone ones

Link to comment
Share on other sites

Errr 4 or 6mm? F\'d if I know

Does change the characteristics of the whole twin turbo system thing if they are much bigger or smaller than normal

Plus theres little restrictor pills hidden in half of them which are allegedly vital, not that it mattered to me since I had half of mine removed, blocked or bastardised anyway. You cant go too far wrong if you spend a little time understanding what each one does and how it all works, if you dont then honestly youre better off leaving it untouched

Link to comment
Share on other sites

  • General Member

[quote name='JoKer said:

hey Marky : this is in the Impreza section : you said turbo\'s as in plural? must be a funky Impreza!


Secondary relief valve too, second turbo\'s in the boot. Guessed was meant for Leggy thread.

fixed :P

but yea will only get a louder BOV noise buy 100%venting atmo (not recomened techincally but fun for a week or two then I reckon you\'ll go back to 50.50

Link to comment
Share on other sites

 swanson-07 said:

Even on 100% vent it sounds like a wimpy fart :(

Try removing the OEM restrictor pill in the BOV vac line if you haven\'t yet. Makes aftermarket BOV\'s more responsive/louder

Edit: Bigger vac hose diameter might help too? I run an HKS sequential/5mm hose/no pill/loud

Editit: Hose 10 mod will have big effect too

Link to comment
Share on other sites

Yea, im running 14psi - both turbos

Execpt im fitting a new turbo intake this week as my secondary has a split causing Limp mode (just on secondary) - BOV sound was quiet still before the split

Split was caused by taking it off to do the knock sensor as its is in the most nasty place and couldn\'t get to it. wouldnt go back on nicely as its done a good 165K

Link to comment
Share on other sites

Its a $380 GFB from a sponsor from here il keep it on as its a bit just to chuck away. It just doesn\'t even sounds like a bov on vent. Ive tried a cheap trumpet same thing no noise. Ive defo got boot goes amazingly ect. You can hear a tiny recurk on 100% recurc. For running 14psi and I\'ve herd other b4\'s and they\'re pretty loud. I just don\'t understand i get what sounds like a wimpy fart that you can bearly hear? Maybe its blocked.

Link to comment
Share on other sites

  • General Member

plumbed in right? pretty sure you have the same one I have and I have no issues with it making noises

tried adjusting the screw on the top/spring pressure etc


Step 1 Aquire GFB hybrid BOV and wear it like bling!


locate OEM BOV




how to make loud noises!

place bung in "return" and let the trumpets do their work (this setup lasted a day)


had to have above setup due to fact BOV was supplied with 34mm? connectors and Brendon at GFB was surprised in the fact his assumption was all WRX\'s were that size, sit and wait for 20mm adapters arrive...

you can see small allen-key below which I found after trying to unscrew it for 15 mins!



rangi mod - Like I said need pipe and spare hose clamp, 1st attempt I cut the existing pipe in half but that left the BOV a bit high and it rubbed on inside of the bonnet



rangi mod #2 - lost my bung and have since tidied up my infamous "plastic-bag" mod (effectively plumbs back 100%) and looks prettier


you will also need a longer vacuum hose to reach way back where I have mine.. (that blue line)

then of course B$\'s are different (you haven\'t said what car you have yet)

[quote name='ReubenH said:

Mint, damn you joker, i want one.

Sadly it\'s quite a different install for the B4, they have the bolt-on-the-intercooler ones remember. But the idea is still the same, "take off old one, put on new one"

Link to comment
Share on other sites

 swanson-07 said:

Can i just remove BOTH of these? the one to the BOV and to the secondary intake hose(if thats that it is)?


Try adjusting first as Joker said.

You could remove the one (left in pic) in the BOV line for now, that will make your BOV louder.

But I wouldn\'t do anything more than that until you get the split intake fixed, or you could just cause more problems. Don\'t mod it till it\'s running right...

Flogging a broken horse...etc etc

Link to comment
Share on other sites

Block that hose on the right, the one which goes back into the intake pipe

Thats the "hose 10" mod

That... thats about all you can do

For super mega volume get a different bov, the gfb ones work good but arent super dom toretto loud compared to the knock off "rfl" ones for example

As for why it is quieter, your b4 has a turbo half the size of the wrx, just less air is coming out (less flow, inertia, whatever) - with a front mount and no bov mine still chattered like a gtst for 5 sec or so, its more there just is f-all air backed up with a tiny turbo and top mount

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...