turbo issues & bypass valve

Charlie Smith charlie at elektro.cmhnet.org
Sun Sep 9 13:21:56 EDT 2001

Earlier, c a l i b a n wrote:
> 	just what is "surging" anyway?  how does it feel?
> 	lately i have noticed that when i really get on the gas
> 	i hear and feel kind of a rumble from the car.  this is
> 	a 2k a4 1.8t avant with an APR chip, BTW.  the rumble
> 	kind of sounds like it's coming from the rear of the
> 	car, and like i said, i can hear and feel it.  it is
> 	pretty subtle and i am pretty sure it subsides a bit
> 	once i reach maximum boost.  i'mn pretty much just
> 	talking about 4th or 5th gear, here.

Don't really know what that is, but it's not turbo surging.

> 	any ideas what, if anything, this might be?  is this
> 	surging?  i also heard from a friend big in the VW
> 	scene that there is come kind of valve that wears out
> 	in a year or so in chipped 1.8t cars, perhaps this is it?

What wears out, is the turbo bypass valve.  Most common
symptom is a honking noise when you let off the  gas, and
greater lag when you get back on the gas.  There's been a lot
of conversation about the "best" Audi part number to use
for this.  The topic has been beat to death over on the S car 
list, and the concensus seems to be to use an aftermarket 
bypass valve.  I might note, NOT the T.A.P. valve which has 
been reported to lose parts and shred the turbo.  I'm using
a FORGE bypass valve on my S6.  I believe I'm using the model
for the 2.7 biturbo, of course you only need one.  Here's
a URL for this:

    - Charlie

  Charlie Smith   charlie at elektro.cmhnet.org  614-471-1418  
  http://elektro.cmhnet.org/~charlie   Columbus Ohio   USA

  95 S6 Quattro  -  24 PSI, RS2 6 speed, and other features  
  96 Dodge Ram   -  30 PSI, w/Cummins turbo diesel

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