Re: K24 and boost - more on WGFV

[QSHIPQ@aol.com]

In a message dated 12/5/99 1:17:38 PM Central Standard Time, 
orin@WOLFENET.com writes:

>  We have a bit of a semantic game here.  The WGFV is only a vacuum
>  switch.  You can label it's ports however you please...
>  
>  I could say you have two pressure inputs (manifold and pre-turbo)
>  and one pressure output (wastegate)... the wastegate gets to
>  see something between the two depending on the duty cycle.
>  
>  With your labels, the port to the wastegate is both an input and an 
output...
> 
>  an output when switched to the intake manifold and an input when
>  switched pre-turbo.

I don't agree with that at all Orin.  With no DC, the WGFV is open to the 
vent, there is no "control" or measure or relevency of this function, it's 
just a simpler device (ie you don't need to plug the vent line, since when 
the vent is open, nothing happens, nothing is measured, the WG doesn't open - 
so it's not an "input", it's just the "off" position.)  When the WGFV is 
operating, the computer measures the input value (PT = manifold feed 
pressure), and actively controls a percentage of that measured value by DC at 
the WGFV (WGFV value = % * PT value from 5% -95%). 
>  
>  If this were an electrical system, the line to the wastegate would
>  definitely be an output and the other two inputs.  The fact that
>  one is usually negative relative to the other doesn't change it.
>  
>  Orin.

But this is a controlled flow fluid DC switch, not an electrical one.  In a 
pressure experiment with a DC switch, you have a feed, a source and a vent.  
The feed is an input, the source is an output, the vent is also an output.  
How would we measure it as an "input" if, regardless of value, nothing 
happens?  I see no documentation of that.  In fact, all FV operations used by 
audi, document a single measured feed, a single measured output, and a vent 
(not measured = not relevent, no value, only closed loop significance). Fuel 
Pressure FV, EGRFV, WGFV (10vt or 20vt).  The values of the "vent" output are 
never mentioned, because they aren't relevent.  There are also no input tests 
at all of vent functions in any Bentley or service manual wrt FV that I've 
seen.

Bottom Line is this:  DC are values that are measured.  They are measured in 
terms of a percentage of feed (input) values which assigns an output value 
(ouput = pressure at top of WG), and excess.  To address the off or open 
switch to vacuum at turbo inlet as an input function has no measurable value 
or function, because this off state doesn't cause anything measureable to 
happen.

Call it semantics, I think it calling a FVDC "vent" an input, only causes 
confusion here. 

HTH

Scott Justusson