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rsrmike rsrmike is offline
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Join Date: Jan 2008
Location: Birmingham, AL
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Originally Posted by beepbeep View Post
BOV won't do anything to prevent vacuum in plenum chamber after the throttle. BOV is installed before throttle.

I personally wouldn't install WG signal after the throttle as it may induce peculiar surging behavior at certain throttle openings on some engines. It will also subject membrane to both boost and vacuum which might and might not shorten it's life, as WG membranes are only ment to be subjected to boost. YMMV.
+1 Makes the most sense of all.

this sort of relates to the debate over where to tap the boost gauge signal...

Some of you guys may have noticed your elec. gauge read .8 or 1.0 bar at 1/4 throttle and relatively low RPM's.

It seems to me you would want the wastegate to open under these circumstances to keep the turbo from sucking more air past the airflow meter and possibly causing AFR issues, granted that would mostly affect a CIS car i think.

Another thing I've noticed when the signal is above the throttle plate is that upon closing the throttle, whatever air surge isn't relieved by the BOV tends to keep the wastegate open longer. A sudden vacuum would most likely cause the valve to slam shut and create a pressure spike on the hot side as the cold side is dealing with pressure spikes on it own from a closed throttle and a spinning turbine wheel. Seems like that may give the thrust bearing some added stress... I dunno certainly no turbo expert here...

I would love to know, on average, how much pressure loss is there really through the throttle body at WOT? Is it really that different? I know it depends on many variables but say an average 930 w/ k27??? Anyone know?

Old 03-18-2008, 01:53 PM
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