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

[Mark Strangways]

I kinda don't see it that way.

I always felt that the wastegate would only see boost when the WGFV is open 
or energized, otherwise it see the "vacuum" stream on the inlet side of the 
compressor. I am not 100% convinced that there is enough vacuum generated to 
do much good.
That has been discussed to death in previous emails, and I ain't going there 
with out proper ammo :-)

Mark S
----- Original Message ----- 
From: "Theodore Chen" <tedebearp at yahoo.com>
To: <Djdawson2 at aol.com>; <bob at chips-ur-s.com>; <s-car-list at audifans.com>
Sent: Wednesday, January 11, 2006 8:15 PM
Subject: Re: [s-cars] While we are on the subject of WGFVs...


> dave,
>
> are you sure that's how it works on the UrS4/S6?
>
> i agree with your description of the configuration, but
> note that the WGFV is plumbed to the lower chamber of the
> wastegate.
>
> the WGFV has three ports on it.  the left port goes to the
> wastegate.  the right port goes to the turbo intake.  the
> bottom port goes to the turbo output.  normally, the
> bottom port is connected to the left port and air can pass
> freely.  normally, the bottom port is not connected to the
> right port and air cannot pass between these two ports.
> when the WGFV is actuated, all three ports are connected
> to each other.  i verified this by applying 12v to the WGFV
> and blowing through each of the ports.
>
> the way the wastegate is plumbed on the UrS4 is that boost
> is used to open the wastegate.  if the ECU wants more boost,
> the ECU implements this by actuating the WGFV, thereby bleeding
> boost off into the intake.  if the ECU never actuates the
> WGFV, all the boost from the turbo goes to the wastegate
> and the wastegate will open at the default pressure.
>
> --- Djdawson2 at aol.com wrote:
>
>> 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
>>
>
>
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