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

[Mark Strangways]

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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