[Biturbos4] All causes to turbo failures known?

Keman keman at interwolf.net
Thu May 13 22:36:57 EDT 2004

>> For the S4, there's only the K04-25 and K04-26 (which are the OEM
>> units for the RS4).  A few tuners are starting to work with hybrids
>> of the K04 housings and exhaust wheels mated with K16 or RS6
>> compressor wheels, but those are just starting to gain popularity
>> (and the housings are still the same).


>> I don't have the measurements but I've seen pictures posted showing
>> the measured difference.  And its not the outlets (I mistyped, if
>> thats what I wrote) but the inlets that are larger... the larger
>> piping goes from the S4 (or RS4) y-pipe to the compressor inlets.

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

>> 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,

>> 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 just think that they are underdesigned in the 2.7T due to the high
>> rate of failures even on stock boost.  And I don't think they are

Well, out of the 30 S4's I've seen in the Michigan area now... only 1 has
had a turbo failure-- ruptured diaphram. All Audi techs remember every S4
turbo set they replace... because it is a nightmare of a procedure, and you
always lose money on it (warranty doesn't pay for the real amount of time
necessary to do it right). Every tech I've talked to has done one maybe two
in the last few years. They each remember them in painful detail. Most
mutter something about having tried doing it with the engine still in the
car, but all claim it's impossible without cutting holes in the fenderwalls
for bolt access. I still want to know how it is that some shops manage this
... even with the engine in front of you, it's very difficult.

Has there been any actual documentation substantiating that say.. out of the
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 they
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 is
representative of what facts.

I mean for example, I just gave my car it's 86k mile oil change tonight.
With that I gave it a very thorough inspection .. sort of my own "10k". I
tightened down an intercooler clamp, which promptly stripped out so chalk up
one new clamp, first I've put on the car. Checked bypass valves, which were
ok. 20k now on these new VW style ones and they appear to be solid
performers. Springs are so strong in them that I can hardly depress them
with my finger shoved into em. Saw that my fuel pressure regulator vacuum
line was frayying at the corner. Not surprising. Put a new length of line on
that. Inspected the entire cooling system, not a single leak. Noticed that
the, yes.. seriously.. stock.. original.. front brake pads are starting to
get a bit thin and are rattling in the calipers. 86k miles on a set of pads
and the rotors still aren't warped... (though I burn through sets of tires
quite a bit because I don't use the brakes, I scrub off speed in the
corners!) ... I contemplated giving it a coolant flush since it's been about
18 months, but I procrastinated that away. But what about this did I notice
the most? Oil leaks. There are none. And I do mean none. Dry as a bone. This
is a sharp contrast from the same year cars I see on a steady basis, all of
whom come in 10k miles late for their 10k mile oil changes ... and their
engines are just falling apart, leaking at every seam. As the miles tick
off, I'm starting to look closer and closer at what regular synthetic oil
changes really do get you. I'm starting to think that this is the key, and
it seems so easy and relatively cheap to do.

But of course, if my turbos are screaming tomorrow ... obviously, I'll think

So... who's really to know? Tell you what though, I'll keep trying to put on
as many miles as I can racing to my goal of passing the 200k mile marker,
and if I get there and beyond... I'll say that regular synthetic oil changes
are what made it possible. That's got to be it. Till then... we can only

Or until someone coughs up some real good documentation substantiating
otherwise... which is certainly possible.

>> necessarily underdesigned with respect to the boost levels run.  I
>> think it has more to do with how well they handle the excessive heat
>> due to their placement on (under) the 2.7T.  On the1.8Ts the turbos
>> are much more well placed. However the compact nature of the 2.7T
>> makes this impossible.

Now heat, heat is an interesting problem. And if I make my 200k barrier, it
could be argued that since I don't have any precats roasting away hot under
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 downpipes
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

>> dealership customers.  If all techs were as knowledgeable as you, a
>> lot less people would have complaints with Audi service :)

Heh, the trick is to make sure that the Audi techs own Audi's themselves. :P

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, half
0W-40W mobil 1. I know Castrol Syntec is not actually a real synthetic and I
actually hate it.. but it was free.. and at that price it's hard to hate...
and while I know some Audi techs say not to run 0W-40, I do know for a fact
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 also have my ford performance engineer friend who has done a lot of
testing in the lab with various oil weights. He says he has never seen an
engine part suffer more wear from running oil that was too thick, but is
scared to death of 0W oils, saying that Ford has done unbelievable things to
try and get cam bearings to survive with 0W-20 and 0W-30. Obviously he has
no experience with high speed turbos and tiny oil passages though...

So.. the last oil change was M1 10W-30, before that it was M1 15W-50, before
that it was Redline 5W-30, before that redline 5W-40, a few M1 0W-30's
before that, maybe a couple of Valvoline 5W-40 synthetics thrown in here or
there. I have a log book of all my oil changes. I'm definitely not staying
with one viscosity. And maybe that will be the key to success.... :P

There is method to my madness...

- Keman

>> -Dave Pramanik

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