which Spring? ( tial bov 50mm related )
Thread Starter
TECH Regular
Joined: Dec 2018
Posts: 456
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From: MIAMI
which Spring? ( tial bov 50mm related ) i was wondering what Tial BOV spring are the boosted guys running? i currently have a 50mm BOV Q Series and i was wondering because i know what spring you use dictates the vacuum correct?
i currently have the plain non painted one which is like -10 psi spring pressure.
any inputs?
( will delete once i have my answer )
plain spring = -10psi if used idle vacuum will be -16in/hg to -19in/hg
i currently have the plain non painted one which is like -10 psi spring pressure.
any inputs?
( will delete once i have my answer )
plain spring = -10psi if used idle vacuum will be -16in/hg to -19in/hg
On The Tree
Joined: Jul 2005
Posts: 161
Likes: 2
From: Wokingham, United Kingdom
No, the spring pressure dictates what pressure differential is needed in order for it to open.
my setup is a centrifugal supercharger, the BOV (also a Tial Q) is fitted with a 2lb spring (often referred to by Tial as a supercharger spring).
When I’m in boost there is equal pressure either side of the throttle blade (because it is WOT), as soon as I snap the throttle shut there is boost pressure on one side of the throttle blade and vacuum in the manifold. The Tial Q uses the vac to pull open the BOV and dump the excess pressure to atmosphere.
Turbo setup is different but that’s not my bag
Regards
Jim
PS - vacuum is defined primarily by the valve events (big cam, small cam, overlap etc etc)
my setup is a centrifugal supercharger, the BOV (also a Tial Q) is fitted with a 2lb spring (often referred to by Tial as a supercharger spring).
When I’m in boost there is equal pressure either side of the throttle blade (because it is WOT), as soon as I snap the throttle shut there is boost pressure on one side of the throttle blade and vacuum in the manifold. The Tial Q uses the vac to pull open the BOV and dump the excess pressure to atmosphere.
Turbo setup is different but that’s not my bag
Regards
Jim
PS - vacuum is defined primarily by the valve events (big cam, small cam, overlap etc etc)
On The Tree
Joined: Mar 2010
Posts: 124
Likes: 8
From: Navarre, FL
You get the spring so it gives you the behavior you want at idle/cruise.
Centri SC you want a super light spring so its open during cruise.... otherwise the thing will create a ton of pressure pre TB cruising at say 3k rpm on the highway. It will also be open at idle, for same reason.
Turbo cars, you see a lot of stock turbo cars use bypass valves that recirculate the air back into the intake tract... you see relatively light springs on them but not as extreme as SC. They also tend to be open at idle/cruise.
With a vent to atmosphere BOV on a turbo setup, you really want a spring that will keep the valve shut at idle and cruise but don't go crazy. -10psi spring is typical for this application and should be good to go! If you had an extreme cam that idled at significantly less vacuum etc, then you may consider a slightly less stiff one, but probably not worth the hassle, it would still vent just fine when its really needed.
Centri SC you want a super light spring so its open during cruise.... otherwise the thing will create a ton of pressure pre TB cruising at say 3k rpm on the highway. It will also be open at idle, for same reason.
Turbo cars, you see a lot of stock turbo cars use bypass valves that recirculate the air back into the intake tract... you see relatively light springs on them but not as extreme as SC. They also tend to be open at idle/cruise.
With a vent to atmosphere BOV on a turbo setup, you really want a spring that will keep the valve shut at idle and cruise but don't go crazy. -10psi spring is typical for this application and should be good to go! If you had an extreme cam that idled at significantly less vacuum etc, then you may consider a slightly less stiff one, but probably not worth the hassle, it would still vent just fine when its really needed.
