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BoxxerSix BoxxerSix is offline
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Join Date: Jun 2006
Location: Ballston Spa, NY
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Originally Posted by NathanUK View Post
Thanks Adam, that makes sense.

Do you think I'm right about the valve helping more when fitted one way than the other when off boost but no high vacuum (pulling away from standstill etc etc)?

Well pretty much the instant you hit the throttle to accelerate the valve closes instantly, so no air would bypass through the valve and into the IC(subsequently bypassing the turbo as you suggested) The valves are pretty much setup so that they open when the plenum hits anywhere from 7 to 15hg, pending on the spring pressure and any adjusting shims that are above the piston(top chamber)

So if you have a super light spring in the valve then yea it might stay open long enough to allow a little air bypass but typically the spring is a bit stiffer to keep the valve sealed against boost pressure and as a result usually once the vacuum drops below the 10hg mark the valve just closes up. If you're accelerating at that low of a throttle input from a stop, the people behind you might think granny is driving

Yea your thinking is correct, but as to whether it is doing that really just depends on how your particular valve is adjusted. You really want the lightest amount of spring pressure possible that still provides enough sealing pressure at the valve seat. This give the best(quickest) valve response. These types of valves usually have a brass or aluminum piston that seals into an aluminum cut seat at the bottom of the main body, so it does take some pressure to maintain a good seal unlike if it had a rubber or some other "soft" type sealing surface.
Adam Hennessy
Old 07-14-2008, 09:28 AM
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