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

Theodore Chen tedebearp at yahoo.com
Sat Jan 14 00:47:32 EST 2006 

is there an echo in here?

sean, james already posted that link a few posts ago.  if
you scroll down, you'll see the link.  :)

in other news, i did a couple of tests on my car tonight:

1.  disconnected the WGFV harness, thereby disabling the WGFV.
as predicted, boost never went beyond 1.2 bar (indicated on
the digital boost gauge).  with a correction factor of 1.2
to account for the 3.0 bar pressure transducer, this works
out to about 6 psi.  that's default boost, and it was 
consistent.

2.  disconnected the wastegate hose to the WGFV at the WGFV.
i left the hose open to atmospheric (so the wastegate lower
chamber sees atmospheric at all times).  i put a short hose
on the WGFV at the wastegate port and clamped it shut, so
that i wouldn't be losing any metered air.  in this 
configuration, i got all the missing boost back and then
some.  stepping on the gas hard resulted in the usual turbo
lag, but when the turbo spooled, the car surged harder than
i've ever known it to, and the boost gauge hit 2.1 (which
is 2.5 corrected, and works out to 22 psi of boost).  it
might have gone higher, but i lifted quickly when i saw how
high and fast boost was rising.  after that, i was careful 
to bring the boost up gradually.  i did about a half dozen 
more runs, and each time i was able to hit at least an 
indicated 2.0 bar (about 20-21 psi boost).

based on this, i conclude the following:
1.  the wastegate is fine.
2.  the bypass valve is fine.
3.  the intake tract has no leaks (of significance, at least)

the problem lies with the WGFV intermittently not actuating
with a duty cycle sufficient to produce high boost.  i do
not know if this is because the WGFV is failing, or the ECU
is not sending a high duty cycle signal to the WGFV.

from my test with the wastegate disconnected from the WGFV,
it is clear that my wastegate does not need vacuum in the
lower chamber to hold 22 psi of boost.

the wastegate looks stock.  it still has the metal plug in 
the top, so nobody has messed with the spring setting.  the
previous owner says he didn't touch the wastegate when he
installed the MTM stage II+ chips, RS2 exhaust manifold, and
pressure transducer, so i believe the wastegate spring is 
stock.

i'm going to replace the oxygen sensor, even though there
are no codes and i highly doubt the oxygen sensor will affect
anything.  but it's old, and may even be the original sensor,
in which case it would have 132k miles on it.

i don't expect that to fix the problem, so i'm probably
going to be borrowing a WGFV from the biturbo S4 to test it.
i want to take the UrS4 to tahoe tomorrow, and i'm hoping
to get my boost back for the trip.  it's probably not a good
idea to drive at high altitude with the wastegate disconnected.

-teddy

--- Sean Douglas <quattro20v at telus.net> wrote:

> James:
> 
> There was a recent write-up in European Car which compared all the N75
> valves on a 1.8T, "the debate continues".
> 
> Scan of article is here:
> http://forums.audiworld.com/s4s6/msgs/49283.phtml
> 
> Sean
> 
> > -----Original Message-----
> > From: s-car-list-bounces at audifans.com 
> > [mailto:s-car-list-bounces at audifans.com] On Behalf Of James 
> > Murray (QA/EMC)
> > Sent: Friday, January 13, 2006 11:37 AM
> > To: Theodore Chen; djdawson2 at aol.com; gailus at mindspring.com; 
> > s-car-list at audifans.com
> > Subject: RE: [s-cars] While we are on the subject of WGFVs...
> > 
> > 
> > Apparently you can get the N75K from TJM for $89.95
> > 
> >  http://www.tjmmotorsport.com/product.php?productid=16184&cat=0&page=1
> > 
> > Question remains for me... What's better for our cars the 
> > N75H or the N75K or is it setup dependent?
> > 
> > /Jamu.
> > 
> > -----Original Message-----
> > From: Theodore Chen [mailto:tedebearp at yahoo.com] 
> > Sent: Friday, January 13, 2006 2:31 PM
> > To: James Murray (QA/EMC); djdawson2 at aol.com; 
> > gailus at mindspring.com; s-car-list at audifans.com
> > Subject: RE: [s-cars] While we are on the subject of WGFVs...
> > 
> > i saw this on audiworld:
> > 
> > Dealer cost for one of these babies is $45, dealer RETAIL is 
> > $80. Cheapest I found online was $56.
> > 
> > Search for part# 034906283H
> > 
> >     * http://www.1stvwparts.com/
> > 
> > 
> > there's also a post that says the 283H is what the dealer 
> > comes up with when you ask for the WGFV for the RS2. 
> > http://forums.audiworld.com/s4s6/msgs/97662.phtml
> > 
> > -teddy
> > 
> > --- "James Murray (QA/EMC)" <james.murray at ericsson.com> wrote:
> > 
> > > 
> > > 
> > > So now to keep the thread alive a tad longer ;-) I ask you guys with
> > > experience, which is the best N75 WGFV to use for the UrS-Cars? The 
> > > stock N75H, or the N75K (RS2 valve) or is it setup dependend?
> > > 
> > > ECS is having a sale their "Race" N75 at $80.00 However I recall
> > > someone saying this was simply the N75H. If I was going to 
> > replace my 
> > > WGFV I'd like to get the best one available...
> > > 
> > > /Jamu.
> > > 
> > > P.S. this article maybe be of interest to some... 
> > > http://forums.audiworld.com/s4s6/msgs/49283.phtml
> > > 
> > > -----Original Message-----
> > > From: s-car-list-bounces at audifans.com 
> > > [mailto:s-car-list-bounces at audifans.com] On Behalf Of 
> > > djdawson2 at aol.com
> > > Sent: Friday, January 13, 2006 11:30 AM
> > > To: gailus at mindspring.com; s-car-list at audifans.com
> > > Subject: Re: [s-cars] While we are on the subject of WGFVs...
> > > 
> > > So... to make a long story short... there IS a vacuum present at the
> > > turbo inlet.  This is the point at which I quit the last 
> > time we had 
> > > this thread.  No one would buy into a vacuum in that area... and I 
> > > threw in the towel.  Paul "Sonic Nozzle" Gailus has provided the
> > explanation.
> > >  
> > > And he still hasn't told us if he was just messing with us the other
> > > night with his dissertation on the Audi sonic nozzle...
> > >  
> > > Dave
> > >  
> > > -----Original Message-----
> > > From: Paul Gailus <gailus at mindspring.com>
> > > To: s-car-list at audifans.com
> > > Sent: Fri, 13 Jan 2006 10:47:56 -0500 (EST)
> > > Subject: Re: [s-cars] While we are on the subject of WGFVs...
> > > 
> > > 
> > > In order to get any airflow from the external atmosphere into the
> > > compressor inlet, the static pressure at the inlet has to be lower 
> > > than the ambient atmospheric pressure.
> > > The only way you can get air flow into the compressor inlet without 
> > > having a static pressure there less than atmospheric would 
> > be to have 
> > > an external source of dynamic pressure supplying high velocity air 
> > > (i.e., another blower).
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> > 
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> 


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