i was gonna buy a BOV but then i saw that it had an 11psi spring it wtf does that mean? if i run less boost than 11psi will it not work?

 

I think what they mean is 11" Hg. People commonly refer to vacuum in psi, but in reality is usually measured in inches of mercury. Just look at your boost/vac guage. I think what is meant is that with that spring, it'll open at when it sees 11" Hg. BOV's don't open under boost, in fact the way they're designed, boost keeps them shut.

 

so it doesnt matter what "psi" the spring is

 

The rating of the spring refers to the vacuum required to open the BOV. And it can be rated at 11 psi and not inches of mercury. If you watch you boost/vacuum gauge you will see how much vacuum your engine pulls under deceleration ( when you completely close the throttle plate when the vehicle is moving ). It should be 11 to 12 psi of vacuum or 22 to 24 inches of mercury. If you live near sea level you want a 11 psi spring and if you live at higher altitudes ( not sure how high, watch your boost/vacuum gauge ) you can try a 9 psi spring. Boost holds a BOV closed and vacuum > 11 psi, with this spring, pulls it open. You only want it to open under decelleration when pressure can build up in the intake track and potentially damage your impeller or your TB plate. A BOV is nice to have with an automatic and more necessary at boost levels > 12 psi but is essential with a manual trans because you close the throttle plate entirely each time you shift which can be very hard on the turbo impeller. It will also help a turbo to stay spooled up during a shift with a manual trans.

 

What he said! ^^^^^^^^

I run a 12 lb spring in the BOV on my non-recirculated draw-thru mass air setup.

 

So with a BOV and spring rating, the pressure refers to the vacuum at which the spring will open? Shouldn't it be -11psi then to make it consistent?

 

Yes. The spring is rated at 11 psi of vacuum so it really is a -11psi rated spring. I think they call it an 11psi spring and the fact that the 11psi is vacuum is understood but that is not very clear or intuitive.