[200q20v] Is it my turbo?

[QSHIPQ at aol.com]

In a message dated 11/19/00 7:05:01 AM Central Standard Time, 
r at cm183316-a.ftwrth1.tx.home.com writes:

> Scott,
>  
>  Both my cars are fine and do not exhibit any anomolies. Now I am not 
>  disputing what you say but my experience is much different than yours. 
>  My cars are stock. Is that the big difference??? If you want to play, 
>  you have to pay?  Both cars pull (push?) the requisite amount of boost 
>  intended by audi.
>  
>  rich andrews sr.
>  

Stock turbs fail too, it's only time (my first car was a 87 5ktq bone stock 
that I bought at 72k, and it needed a turbo).  Not sure the definition of 
"anomolies" but I'd highly suggest that you take off the intake boot to the 
cold side of the turbo and ck radial play, and look for nicks in the turbo 
inlet blades (you are most definitely a coupe standard deviations from the 
mean.  You don't have to believe me, call any rebuild shop;).  As a rule, KKK 
units are very beefy for the audi I5 application, but not bulletproof.  
'Usually' a turbo will slowly lose boost over time, what audi did was 
overspec the sizing of the turbo and it's map, which then allows the WGFV to 
overcome the turbo wear, then mileage like yours *can* happen.  IME, it 
rarely does.  

That said, the k24 is not as beefy as the 26.  The bearings and shaft are 
tiny in comparison to the 26, and the k24 will heat soak quickly.  

Religious synthetic oil changes and inspection of rubber connecting parts 
(leaking causes overboost) and bypass valves will make turbos last as long as 
possible.  That still isn't forever, nor close to it.  IME, the mean failure 
rate of the turbocharger units is 150k.  +/- depends on a lot of factors 
(including luck), but a turbo can handle mods quite easily if those mods 
don't exceed the turbo MAP profile.  On the MC cars (86-89.5), 2bar (14psi) 
is well within the limits of that map.  On the k24 the upper limit is 
2.2barPR which it can do quite well, but 2.4barPR is off the turbo map (big 
no-no).  That doesn't leave much margin for error in terms of leaks or BV 
failures.

HTH

Scott Justusson
QSHIPQ Performance Tuning
Chicago