need help setting up blow off valve !!!

[H1GHROLLR]

hey people i got my vn running today but when i was reving it it was doseing

how do i adjust a BOV properly, i have never played with one before so i dont

have the first clue, should it be open on idle ? any input will be great cheers

[4A10SHN]

Did you try what I said?

[H1GHROLLR]

nah my farkin msn disconected :(

[Jiblet]

bov shouldn't be open at all (until the pressure opens it)

you want it to be tight enough to hold the boost but not too tight that it won't let the air escape when the pressure builds...

a very quick google search comes up with :
http://www.alltrac.net/tuning/bovfaq.html

not sure if that helps, if not, google is your friend...

[H1GHROLLR]

ok so i had a play around with the BOV last night with the car stationary as its not driving yet and when i set it soft it is open on idle then shuts on rev and opens when you lift off should this happen ? also when i wound the spring tight it dosnt open and dose's if i rev it hard ? is this because the turbo is not under load and just free revving ? should i just start with it staying open and keep winding it untill it just shuts ? this should be the softest possible setting i can be running , correct ???? cheers

[d1_drifter]

Can you see the brass piston through the vent?

On idle, start at fully soft and wind till the vent is fully covered by the piston. That is your base setting and from there you can fine tune it to suit your boost when the car is driveable.

[H1GHROLLR]

cheers mate i will try it out tonight , thanks heaps for your help , yes i can see the piston and i can see when it seals so should be easy to try out your method

[Jiblet]

yeah it shouldn't be open on idle... it will just leak air which is not what you want

[H1GHROLLR]

all good i got it sorted now , i thought some BOV do stay like 1mm open on idle , and as soon as you touch the pedal they shut ?

[Z2TT]

BOV should be totally shut on idle, shut under boost, and vent when you let your foot off the gas after boosting.

What is happening is that when vacuum is at it's highest on idle, it is causing suction on the diaphragm which slightly opens the valve, when you give it a touch of the throttle, vacuum decreases and the BOV shuts.

Adjusting the screw/bolt for the spring on the BOV may help.