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

[Theodore Chen]

mark,

what i'm saying is that the wastegate port of the WGFV is
always connected to the boost port.  when the WGFV is 
energized, the intake/vacuum port is connected to the
wastegate port as well, which should reduce the pressure
seen by the wastegate (whether it's a lower positive pressure
or a negative pressure, i don't know, but either way, it
will reduce the tendency of the wastegate to open).

you can have a positive pressure applied to the wastegate
and still not open the wastegate.  the pressure in the lower
chamber has to overcome the pre-load of the wastegate spring,
or the exhaust pressure has to force the wastegate open.

-teddy

--- Mark Strangways <Strangconst at rogers.com> wrote:

> Well, if in fact the wastegate port of the WGFV exposes to all three ports 
> on the WGFV while "Energized" with 12 volts, then I will have to expect that 
> Dave know what he is talking about. Hard to believe that valve has a venturi 
> built-in to it.
> It would have to otherwise the WGFV would be exposed to boost off the scroll 
> of the compressor and would have pressure applied to the underside of the 
> diaphragm resulting in LESS boost which, as we know, is not the case 
> therefore Dave must be right.
> 
> This is fun isn't it.
> Now, anybody have a used WGFV that they can terrorize in the name of science 
> :-)
> 
> Mark S
> ----- Original Message ----- 
> From: "Theodore Chen" <tedebearp at yahoo.com>
> To: <Djdawson2 at aol.com>; <s-car-list at audifans.com>
> Sent: Thursday, January 12, 2006 11:03 PM
> Subject: Re: [s-cars] While we are on the subject of WGFVs...
> 
> 
> > dave,
> >
> > just want to make sure we're on the same page here.
> >
> > we agree that in order to increase boost, the ECU actuates
> > the WGFV to reduce pressure in the WGFV-WG hose.
> >
> > if i understand you right, you're contending that rather
> > than just bleeding off boost, actuating the WGFV causes
> > a vacuum to be created in the WGFV-WG hose, which helps
> > to hold the wastegate shut.
> >
> > in other words, rather than just reduced positive pressure,
> > you're saying there is negative pressure in the WGFV-WG
> > hose when the WGFV is actuated.
> >
> > i have no opinion on that point, and i don't disagree with
> > you.
> >
> > you said:
> > "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."
> >
> > agreed.
> >
> > "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."
> >
> > my understanding is that the boost port of the WGFV is always
> > open, and so is the wastegate port.  the only port being
> > controlled by the WGFV is the intake port, which is normally
> > closed.  when the WGFV is actuated, the intake port opens and
> > is connected to the other two ports.  i verified this by
> > testing with a 12v source and blowing through the ports.
> >
> > i would describe it thusly:
> > "If the ECU decides that conditions are not good for high boost operation, 
> > the
> > ECU begins to reduce the duty cycle of the WGFV,
> > cycling the vacuum port closed, reducing the vacuum and
> > increasing boost passed 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."
> >
> > would you agree to that?
> >
> > this is an important point, because your earlier phrasing
> > implies that actuating the WGFV (increasing its duty cycle)
> > reduces the wastegate's ability to remain closed (and thus
> > causes the wastegate to open).  i believe that increasing
> > the duty cycle of the WGFV increases the wastegate's ability
> > to remain closed, and this is consistent with your later
> > observation that unplugging the WGFV (reducing its duty cycle
> > to zero) causes the wastegate to open at low boost.
> >
> > sorry for belaboring this point, but it is more than academic
> > to me because i have been trying (off and on) to fix this
> > freakin' car for some time.
> >
> > -teddy
> >
> > --- Djdawson2 at aol.com wrote:
> >
> >> In a message dated 1/11/2006 6:42:23 PM Mountain Standard Time,
> >> tmullane at gmail.com writes:
> >>
> >> Teddy is  correct.  Unplugged, or without voltage from the ECU, the
> >> WGFV allows  boost through to the WG, opening it.
> >>
> >> I agree, and stated that in my response to Teddy.  Yep, default  mode... 
> >> if
> >> something isn't working right, the ECU (and the mechanical design) 
> >> default
> >> to
> >> a setup that allows very little boost.
> >>
> >>
> >> When voltage is applied, the valve opens the third port, allowing boost 
> >> to
> >> both the WG and into the intake boot.  This bleeds enough pressure off so
> >> that
> >> the
> >> WG does not open.
> >>
> >>
> >>
> >> So, are you suggesting that "bleeding off pressure" is the only way the 
> >> WG
> >> remains shut?  If that is the case, you're suggesting that the WG spring,
> >> and
> >> only the spring, is responsible for holding the WG shut.  That being  the
> >> case, how would you explain the fact that we are capable of running 
> >> higher
> >> boost
> >> levels than the spring alone (no WGFV or ECU input allowed) can 
> >> maintain?
> >>
> >> Yeah, Mark is right... this has been beaten to death.  But I'm not  quite
> >> sure how anyone makes the logical leap between a WG spring that will only
> >> allow
> >> 14 or so psi by itself... and the fact that we can run double that with 
> >> the
> >> WGFV functioning as designed.
> >>
> >> The ONLY way the spring can be assisted, from the bottom of the WG 
> >> diaphragm
> >>
> >> to allow more boost than the spring alone, is by introducing a  vacuum. 
> >> That
> >>
> >> is simple fact.
> >>
> >> Dave (and I'm smiling about this age old topic)
> >>
> >
> >
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> 
> 


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