[s-cars] While we are on the subject of WGFVs...

[Djdawson2 at aol.com]

FWIW...
The WGFV is basically a switch used to control the boost level at which the  
WG will open.  It is also used to "increase" or "decrease"  the  strength of 
the WG spring when required.
 
There are 3 ports on the WGFV.  1 of the ports goes to the  wastegate, and 
basically is the means by which the ECU's desires are  communicated to the WG.  
The other 2 ports provide the ECU the mechanical  means to either "strengthen" 
or "weaken" the wastegate spring.  1 of those  2 ports goes to vacuum, found 
at the turbo inlet.  The other 1 goes to  boost, found on the scroll of the 
turbo's compressor housing.
 
If the ECU decides that all conditions are good for high boost operation,  
the WGFV allows the vacuum source to pass through it to the WG, and this  
effectively increases the WG's ability to remain closed.  Net result... the  WG 
remains closed to a higher boost level than would be attainable with the  spring 
alone.
 
If the ECU decides that conditions are not good for high boost operation,  
the WGFV begins to cycle the boost port open, allowing boost to pass through it  
to the WG, and this effectively decreases the WG's ability to remain  closed. 
 Net result... the WG remains closed to a lower boost level than  would be 
attainable with the spring alone.
 
If you take the ECU out of the picture by removing the WGFV, or  
disconnecting the line to the WG, you will find that the stock WG spring will  allow about 
14-15psi of boost.  If you are running a header, you will  discover that a 
stock WG spring is capable of holding the WG shut up to 25-28psi  of boost.  
This can only be due to the fact that the exhaust restriction,  and therefore the 
pressure built up between the cylinder head and the  turbine, is greatly 
reduced.
 
Hope that helps,
Dave