[s-cars] Boost cutout progress...

[Scott Justusson]

 IME WGFV fail regularly, usually either from getting stuck in a set position or getting weak in frequency-regulation ability in chipped applications.  You can sometimes get 'a change' to confirm suspicions by taking it out, cleaning it really well with brake clean and compressed air and putting it back in.  Also, remember to check the hose from the turbo to the WGFV and the hose from the WGFV to the WG for any cracks (they are hard to see with the temp wrap on them).  If those are leaking the WGFV can be working just fine, but you really have no accuracy in 'regulation' of it and the ecu never sees the problem.

 

I'm a fan of the connect test, not the pinch test, as I describe in my Sept 2 post on this issue I reposted below.  If the car reaches 'baseline spring pressure' without any symptoms of a cutout event, you can reasonably come to a couple conclusions, your hoses are fine, and your likely culprit is a bad WGFV.  I see enough bad WGFV on high boost S cars, I keep more than 1 spare known good handy at all times.  Could be a sea level thing, but IME they fail on all 20vt cars, I do at least a couple replacements a year.  For replacement, the RS2 WGFV is the fastest, the 1,8t the slowest reacting.

But for testing purposes, you can use a WGFV out of almost any turbo car from 1991> as they all operate the same and have the same connector, the only difference is the mounting tab IME.  

HTH

Scott J
20vt engines apenty 

 

-----Original Message-----
From: Scott Justusson <qshipq at aol.com>
To: forgied <forgied at shaw.ca>; s-car-list <s-car-list at audifans.com>
Sent: Sun, Sep 2, 2012 4:08 pm
Subject: Re: [s-cars] Overboost and Wastegate Springs


Overboost is not usually a WG spring problem on a 20vt.  Best test given the OP is to bypass the N75 valve from the boost hardware (disconnect the turbo outlet from the N75 valve and the WG feed from the N75 valve and join them together).  This should allow exactly 1.9bar (absolute pressure) boost or ~14psi.  If this happens, then the WG is operating correctly, it's the N75 valve that's likely the problem.  The OP sounds like an N75 valve that is stuck in a partially 'closed' (add boost) position,or a leak in the line that feeds the ECU pressure transducer.  With either of the above the car will 'overboost' beyond the normal software boost profile design parameters.

A fix best done sooner than later, or expect a sudden loss of power due to some more basic loose-metals problem.

Cheers and HTH

Scott J
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-----Original Message-----
From: djdawson2 <djdawson2 at aol.com>
To: jim <jim at almgt.com>; s-car-list <s-car-list at audifans.com>
Sent: Wed, Sep 26, 2012 1:26 am
Subject: Re: [s-cars] Boost cutout progress...


Jim,

Pinching off the line to the WG simply takes the Engine Management system out of 
the boost equation.  Further, it reduces the max boost you will produce.

IMO, because you've reduced the max boost level (probably making about 15-17psi 
max), you are not allowing boost to reach a high enough pressure for the ECU to 
cut the fuel.

The pro: You aren't getting boost related cutout.
The cons: 1) You aren't getting max boost. 2) The ECU is unable to protect the 
health of your engine if it encounters extreme/dangerous conditions, like 
overheat, high intake air temps, etc...

WGFV?  I'd say it's a good suspect.  However, I can't provide BTDT experience, 
as I've not encountered a failure in my experience.  Perhaps others can comment.

You're getting closer... good luck.

Dave