[urq] WX, Wastegates testting.

[urq]

... I read that the OP was applying pressure to the bottom of the WG ... this IS 
exactly the way it is intended to work.  I think you are thinking about the 
fitting on the cap ... but even there you should be able to operate the 
wastegate ... you'd need vacuum rather than pressure to open though.  I can't 
imagine what mechanism applying pressure/vacuum to the upper chamber would have 
on possible damage to the WG ... all the diaphragm operates on is the difference 
in pressure between the top and bottom chambers ... biased by the WG spring of 
course.

You should not expect the lower chamber of the WG to hold pressure, but if you 
suspect the diaphragm is leaking you can apply pressure or vacuum to the fitting 
on the cap, and it should hold whatever pressure you apply.  


It is a fairly simple matter to tweak boost on the WX.  Most of the older cars 
have the adjustable spring perch in the WG cap, which can be used for minor 
tweaking.  Another thing you can do to "stiffen" the WG spring is to attach a 
closed length of hose to the WG cap ... a longer hose gives a weaker spring.  I 
have an adjustable pressure regulator plumbed into the fitting on the cap, which 
is probably a better way than monkeying around with hose lengths.  If you want 
more info on this do a search on Schrapnell, or is it Schrappnell in the 
archives.  


Steve Buchholz



________________________________

Sent: Wed, October 20, 2010 8:17:08 AM
Subject: Re: [urq] WX, Wastegates testting.

-----Original Message-----
From: Ed Torres 
Sent: Wed, Oct 20, 2010 8:44 am
Subject: [urq] WX, Wastegates testting.

Hi Guys,

quick question...on wastegate:
I am trying to set my WG to open at 14psi...
I put air pressure thru the bonjo bolt below of the WG but doesnot hold pressure 

The diaframe is good since, I checked no visual cuts, plus it holds vacume from 
the top...

Is that normal that it will leak thru the piston? or my piston is worn-out?
(i think is a piston that goes up & dowm..I have not take it apart yet)


You're going at this the wrong way...  The wastegate doesn't open and close only 
due to pressure on the diaphragm.  In fact, if you were to pressurize the 
diaphragm enough to open the wastegate, I believe you would rip it.  The 
diaphragm and ports exist only to "modify" the effect of the wastegate spring... 
to make minor adjustments to opening and closing by "strengthening" or 
"weakening" the overall effect of the spring.

The heavy lifting is done by the exhaust pressure applied to the bottom of the 
WG.  Unless you know the exact relationship between exhaust pressure and boost 
(and you don't, nor do I), you will not be successful in setting up the WG on 
the bench to provide 14lbs of boost.  You need to do this by running the car and 
adjusting the preload on your WG spring.

hth,

Dave