Thread: BOV orientation
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mark houghton mark houghton is offline
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Join Date: Jul 2008
Location: Central Washington State
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Originally Posted by JFairman View Post
I remounted my BOV sideways, but I did a couple other things that improve drivability at the same time so it's hard to say if it made a difference.
Seems to work about the same, but my 25mm TurboXS "bosch replacement" BOV doesn't have a real light spring.
It does have some spring tension adjustment and it's easy to screw the top off to try lighter springs.

A BOV that has more surface area on the back side or vacuum line side of the piston would work better this way with a light spring because when boost comes on there would be more boost pressure pushing the piston shut from the back side.
The brass piston in the one I have has the same surface area on the both sides so mine needs a fairly strong spring to hold it shut while accelerating with boost.
There are so many aftermarket blow off valves to choose from these days... who knows which one would work best.

Seems the Synapse BOV is well liked by those that have tried it.
The BOV I purchased is from a company called Tuning Alliance. Never heard of them, just got a good deal on Evilbay. 34mm piston, the top being larger than the bottom where it seals, screw top and stiff spring. Would be easy enough to modify as fully adjustable. See the BOV/bypass valve on the left in the picture:

I'm not entirely sold on the whole concept of my post. Rethinking everything, the turbo may spin maybe a little faster with no load on it (when not compressing air), so perhaps there would be a little less lag in getting the turbo up to speed when the BOV closes. Unless I hear more than one success story, I'll install the valve however it best fits functionally and esthetically.

More concerning to me are the occasional comments about these small BOV's not being large enough to pass enough air to really accomplish what we think. Maybe that's why Porsche used the boat anchor instead, to really move some air and prevent turbo stall. Are we fooling ourselves, and are our turbos stalling more with the aftermarket BOV's we install, and the only real benefit of this retrofit is in reducing the quantity of air that needs to be compressed?
Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 12-08-2009, 10:03 AM
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