Thread: BOV orientation
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billjam billjam is offline
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Join Date: Aug 2007
Location: Perth, Western Australia
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Originally Posted by mark houghton View Post
Thanks Bill. Your gauge looks like 23.6 inches of vacuum when the throttle plate is closed, and about 7.9 inches at cruise. Where is your boost line connected...directly beneath the throttle body plate or further downstream in the intake manifold?

Assuming I will see similar vacuum at cruise, then I would want to calibrate my spring tension to an equal and opposite force, which would be 3.88 Psi to counteract the vacuum and keep the piston closed. Pretty light spring tension, yes.
My boost/vacuum connection is at the throttle body and below the butterfly (port III in the diagram).

I have tried a few locations (including brake booster) but this gives best results for me. When tee'd into the brake booster hose at the engine, gauge indicated 0.2 to 0.3 bar LESS boost for some reason. Port III boost readings are also very similar to standard boost gauge, which is some degree of comfort.

1988 Carrera - 3.6 engine (with ITBs, COPs, MS3X) and a whole set of turbo body panels waiting in the attic.
Day job ...
Memories: '68 912, '72 911T, '80 911SC, '84 911, '85 930, '86 930, '87 911
Old 12-08-2009, 03:55 PM
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