What's This/What's It Do?

Phil Rose pjrose at frontiernet.net
Mon Apr 11 22:01:01 EDT 2005

At 8:21 PM -0400 4/11/05, Kneale Brownson wrote:
>Guess I misunderstood terminology.  What I replaced last fall and
>previously a couple times in the several years I've owned this car
>apparently was the Turbo Bypass Valve (black plastic POS) that's plumbed in
>with hose clamps.   Appears in SJM's diagram at
>http://www.sjmautotechnik.com/trouble_shooting/20vwgcnt.html  . So the
>arrow in my pix points to the WGFV.  Since it's all corroded and some of
>the corrosion on the top seems to be cracked, I presume I should replace
>that.  What all do I need to replace that?

The corrosion doesn't necessarily mean anything ominous.  What you 
see on top is just a piece of plated steel (mounting bracket). I just 
took a look at mine, which is only about 4 yrs old, and it looks 
pretty corroded, too, but works fine. I'd do the resistance 
check--that's easy and you can do that without removing the valve. 
The ecu output tests are pretty easy to do, also. AFAIR, the wgfv is 
a dealer-only part. You might check with Scott M about that. The 
replacement I bought (from Carlsen Audi way back when) cost about $70 
(so best to make sure you really need it). At the time, there was 
only one of 'em available from Audi's USA warehouse and they were 
scarce items in the following months. What's happened since then is 
anyone's guess.


>At 06:24 PM 4/11/2005 -0400, Phil Rose wrote:
>>At 5:54 PM -0400 4/11/05, Kneale Brownson wrote:
>>>The actual valve is relatively new--installed last fall.  This connection
>>>is located on a pipe that seems to be metal closer to the turbo and fabric
>>>covered hose on the other side of where this connection is mounted.
>>Not sure what you're saying--i.e., what valve was replaced last
>>fall--was it the wgfv? In any case, the connector (with arrow) shown
>>in your photo is--without any doubt--attached to the wgfv  (aka:
>>wastegate frequency valve).
>>>At 04:20 PM 4/11/2005 -0400, Phil and Judy Rose wrote:
>>>>At 3:24 PM -0400 4/11/05, Kneale Brownson wrote:
>>>>>When I had intermittent boost (1.3, 1.4  and then 1.6-1.7 and so on) a
>>>>>month ago, Ingo suggested the waste gate frequency valve electricals, so I
>>>>>attempted to take this connector
>>>   >>http://www.pbase.com/kneale_brownson/image/41941930   apart 
>>>for cleaning.
>>>>>Because of the close quarters, I couldn't hold the spring 
>>>>>retainer down and
>>>>>take the connector off.
>>>>>Anyway, what's the connector indicated by the arrow in the pix do and what
>>>>>do I probably need to replace?  The fixture onto which the connector goes
>>>>>looks corroded at least on the outside, and some of the corrosion appears
>>>>>cracked from my efforts to get the connector off a week ago.
>>>>    man that's some uuuugly old stuff down there. How old is that car,
>>>>That of course, is the wastegate freq. valve connector. The wgfv is a
>>>>solenoid valve that regulates the amount of boost pressure admitted
>>>>into the lower chamber of the wastegate ; it has a duty cycle that's
>>>>determined by a fluctuating voltage that's varied by the ecu
>>>>according to its boost map . When the valve fails to operate, its
>>>>default (i.e., no voltage) position is wide open, in which case the
>>>>wastegate will always see the full boost pressure pushing on it; and
>>>>therefore it opens prematurely to limit the boost. By "prematurely"
>>>>is meant there'll be a maximum boost of 1.3 or 1.4 bar rather than
>>>>the normal 1.8 bar. This low-boost mode of failure is a safety
>>>>factor. From the looks of your wgfv "relic", I wouldn't be surprised
>>>>if it needs replacing; however since you report boost is as low as
>>>>1.0 or 1.1 bar, I suspect that something else-- besides (or in
>>>>addition to) the wastegate valve--is misbehaving. You could do an
>>>>audible ("click/clack") test of the  wgfv operation by following the
>>>>ecu "output tests" procedure described in Bentley or in Scott M's web
>  >>>site.  A silent valve is a sure sign it needs to be replaced. There's
>>>>also a resistance spec you can check (resistance measured across the
>>>>two terminals of the valve). But look for other problems: a loose
>>>>boost hose clamp, etc.
>>>>*  Phil & Judy Rose           Rochester, NY  *    
>>>>*        mailto:pjrose at frontiernet.net       *
>>Phil Rose
>>Rochester, NY
>>mailto:pjrose at frontiernet.net


Phil Rose
Rochester, NY
mailto:pjrose at frontiernet.net

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