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

[Mark Strangways]

humm
I know I was leaving but...
Have you ever measured what vacumm exists in the wgfv to wastegate line 
during a high boost run ?

Might be fun at the next dyno day, yours or mine.

Mark
----- Original Message ----- 
From: <Djdawson2 at aol.com>
To: <tmullane at gmail.com>
Cc: <S-CAR-List at audifans.com>
Sent: Wednesday, January 11, 2006 10:24 PM
Subject: Re: [s-cars] While we are on the subject of WGFVs...


> In a message dated 1/11/2006 7:10:43 PM Mountain Standard Time,
> tmullane at gmail.com writes:
>
> I can't  explain the mysteries of the universe, but I do know that the
> basic WGFV  functions as Teddy and I described it.  When power is
> applied, all  ports are joined.  All you need is a WGFV, a battery, and
> breath of  air to test and confirm this.
>
> Tom,
> I am well aware that what you and Teddy have stated is true.  I have 
> never
> debated that fact.
>
>
>
> Remember  that the spring only needs to hold the WG shut against
> exhaust gas pressure  inside the exhaust manifold.
>
>
> I am also well aware of this fact.  I would guess that I've been to as 
> many
> turbo system design seminars as anyone on this list... as fleet 
> management,
> design, and specification (mostly diesel and natural gas turbo vehicles) 
> is 75%
> of what I do for a living.  I'm not trying to be conceited, but I do know
> what I'm talking about when it comes to turbocharging systems.
>
>
>
>
> The only  boost to affect the spring comes from the WGFV when it is 
> closed.
>
>
> Agreed.
>
>
>
> Exhaust  manifold pressure is related to the exhaust system flow, not 
> boost.
>
>
> Agreed... partially.  As boost builds, so does exhaust manifold 
> pressure...
> and the only relevant pressure to our discussion is that found  between 
> the
> cylinder head, and the turbine wheel.
>
>
>
>
> Think about what happens when you disconnect the WGFV from the WG  -
> boost goes sky high.
>
>
> No... it will only build to about 14-15psi.  That is why it is called  a 
> "1
> bar" spring.  The spring is designed to provide just enough "push" to 
> hold the
> WG shut to 14.7psi... no more, no less.  AND, it only performs to  this 
> spec
> if it is used in the original configuration... meaning EM and  turbo. 
> Throw a
> header and a different turbo into the mix, and the  pressures change... 
> and
> so will the boost level allowed by the spring.
>
>
>
> In this case, the only thing that can overcame the spring and open the WG 
> is
> pressure of the exhaust inside the manifold.
>
>
>
>
> Yep.  But knowing that the spring is only good for 14.7psi of boost
> (unassisted), how would you explain being able to run double that?  The 
> only
> explanation is vacuum to the bottom of the diaphragm of the WG.  I did  a 
> little
> search on the web, and the best drawing I could find without turning  this 
> into a
> big project, was this:
>
> _http://www.2linc.com/venturi_vacuum.htm_
> (http://www.2linc.com/venturi_vacuum.htm)
>
> As you can see in the diagram, if all 3 ports are open (which they are in
> the WGFV when power is applied) you have created a venturi vacuum 
> generator,
> with pressure entering the side of the fixture, just like our WGFV.  This
> creates the vacuum that holds our WGs shut.
>
> You can prove all of this to yourself with one simple test.  Clamp or
> disconnect the line to your WG and see what boost you can achieve.  It 
> will  only be
> about 15psi.
>
> If you want to take it a step further, connect a vacuum gauge to the line
> between the WGFV and the WG.  You WILL see vacuum there, and it is what 
> helps
> the spring keep the WG shut at boost levels above 15psi.
>
> I hope this email doesn't sound blunt... it wasn't intended to... I do 
> enjoy
> the discussions, and consider them friendly.  I hope you do  too.
> HTH,
> Dave
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