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Get the leeches - my WG is bleeding
In a message dated 96-09-02 15:42:30 EDT, rdh writes:
<< An empirical observation from my UrQ. Try as I might, I can build
neither significant pressure nor vacuum on the manifold-side of my UrQ's
wastegate, using my little hand pump. Yet if I connect to the atmospheric
reference port, it will hold pressure/vacuum all day long. (And the waste-
gate operates just fine.) I have concluded that the Audi wastegates some-
how flow ("consume") gas as part of their operation. Which would explain
the monster 8 or 9mm hose connection to the wastegate, vs the tiny 4-or-so
mm atmospere port . . .
Then Phil writes...
>>>>> Just did the final test - blow into the lower chamber, check for
> in the upper chamber... yup, pressure in the upper chamber.
May not prove anything. Apply pressure to the upper chamber, seal it off,
see if the pressure holds.>>>>>
.... The WG is a crude but effective boost control device... You gentleman
are right on, but Orins' test is also valid.... If you apply pressure/vacuum
to the bottom of the wg and get no fluctuation at the top, then that may tell
one nothing, even if the pressure/vaccuum goes away when connected to the
bottom over time.... What is significant of Orins' test, is that when he
applied pressure/vacuum to the bottom of the WG he got A reading (regardless
of what the reading was) at the top, a true indicator of a WG diaphram
prollum... The reason that the WG bleeds at the bottom without a visable
leak is that the pressure/vacuum leak is occuring thru the shaft of the WG
valve..... The boys at audi decided that a valve guide seal might just melt
down (here is a engineers nitemare) and is hardly necessary with a major feed
at the WG...... The key is to get a measurement between the two chambers, I
find the bottom to top test an easy one, cuz you can rule out any other
possible leak than the diaphram that way....