[Biturbos4] All causes to turbo failures known?

dap128 dap128 at hotmail.com
Thu May 13 23:03:50 EDT 2004

> Interesting. I'm going to hit up the parts counter guy tomorrow...

Not sure if US parts depts will have info on these as they are Euro parts
(but who knows, maybe they can look them up).  But there are plenty of
vendors selling K04s and inlet pipes so you can always look to them for

> >> I've seen ATPs indications on developing a GT25 kit and would
> >> certainly like to see that development.  That's why I said at
> >> present there isn't a kit using larger turbos... hopefully something
> >> will materialize.
> It's a whole system that's needed. Chip, turbo, exhaust housing, turbine
> outlet .. that's a lot of R&D, and probably why they call it a stage III
> to get you ready for the $6000 price tag. :P
> And I bet it'll be awesome ... but... heh. For that much money... not
> including installation... they're not going to sell a lot of those kits,
> IMO.

Actually with programming and fueling most K04s kits are already $6k and
that's exclusive of downpipes and exhaust manifolds.  So I'd expect a kit
using GT25s to be closer to $10k all said and done (and then labor on top of

> >> The diameter of the shaft is the same but the temperature restrictor
> >> (hollow portion within the shaft) is a different shape/size, thus
> >> leaving more solid material in the shaft and making it less prone to
> >> failure.  I've seen schematics of it posted on Audiworld, but again,
> >> I don't have a link handy. If I can find the diagram, I'll be sure
> >> to send the link to this group.
> I'm definitely interested...

I found what I was looking for...

Page 30 has the info on the K04 vs K03 differences.  The rest of the .pdf
has LOTS of nice info on the RS4 and changes made to it over the S4.

> Has there been any actual documentation substantiating that say.. out of
> 1455 or so Avant S4 biturbos brought into the US, say... 145 had toasted
> turbos in 100k miles? 500 of the 5000 or so sedans? ... my gut feeling
> remains that when someone loses a tubo, it's such a costly venture that
> scream pretty loudly about it... and then, you gotta figure out /WHY/ it
> died. Bad design? Bad maintanance? It's so hard to really know what data
> representative of what facts.

Well, in my small circle of local S4 owning friends 3 of 5 have experienced
turbo failures (myself included).  Not good odds.  Plus, I've heard of far
too many failures from others on Audiworld.  Granted enthusiast sites isn't
be best random sampling of S4 owners, but still the failure rate seems
disturbingly high.  Its pretty commonly accepted that stock turbos are one
of the main weaknesses of the S4 (the other being the 1-2 synchros and

> Now heat, heat is an interesting problem. And if I make my 200k barrier,
> could be argued that since I don't have any precats roasting away hot
> the hood, that's why I made it.
> Believe me, if I could tell everyone right now to go out and break the law
> big time and take your precats off, spend the $1200 on aftermarket
> and oh don't forget the thousand dollars of labor, and then the $500 check
> engine light removal chip, I would. But that is a bit expensive and quite
> illegal. And... what if the turbos died a week later? :P

I'm with you on the precat removal as a good thing for reducing heat in the
engine bay.  And the performance gains are a nice bonus too :)

> Heh, the trick is to make sure that the Audi techs own Audi's themselves.
> Btw, for those still trying to figure out the best oil weight to run in
> their biturbos perhaps looking to glean what it is that I run, this might
> blow your mind: in this particular case it's half 5W-40 castrol syntec,
> 0W-40W mobil 1. I know Castrol Syntec is not actually a real synthetic and
> actually hate it.. but it was free.. and at that price it's hard to
> and while I know some Audi techs say not to run 0W-40, I do know for a
> that every biturbo that makes it to our shores has it in the oil pan from
> the factory. They are also aware of this and are just as puzzled as I am
> over what weight to actually run.

I like M1 0w40 as it is the closest fully synthetic oil to what the manual
list as recommended weights and fully meets the required specs listed in the
manual.  I had no idea that 0w40 was factory fill though.  Good to know.

-Dave Pramanik

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