[BiturboS4] Blown turbos

[Edwards, Dave]

Carter,

That depends what you mean by 'blown'. Turbos which have truly failed will
result in serious loss of power and possible engine damage if parts of them
get into it. However much more typical is the case when damage first starts
to happen to them. Typically this is either from general wear, lack of
lubrication or overspin due to air leaks. The first thing you would notice
is an increase in noise.

On a healthy S4 you should only hear the turbos when the windows are down.
You'll hear a feint whistle at low revs, nothing more. As soon as the boost
comes in, the general engine/exhaust/wind noise should drown anything out.
If you start hearing the whistle more loudly, the turbos are starting to
die. If you hear a siren noise they are dying. If you hear any metallic
noise they are nearly dead.

As I mentioned, air leaks are a common cause of turbo problems. To
illustrate this, a friend of mine recently replaced his TBB with an APR
bipipe and found a tear in the TBB. At the same time the turbos became
noisier (he can hear them whistle with the windows closed), and of course he
is getting a lot more power. He thinks the TBB could have been leaking since
he bought the car (used) a year ago, which is why he didn't notice it.
Fortunately for my friend this gives him a (welcome) excuse to have K04
turbos fitted and get a 400bhp+ car!

And that's the main problem. You'll only notice major air leaks. For minor
leaks, the ECU manages to keep the boost at the demanded level, but as a
result the turbos are working harder (increased air flow - more spin). For
more serious leaks there will be a loss of power (and often the ECU will
detect it and go into limp mode).

So what are the solutions?
Firstly regular checks, but this is difficult: Some TBB leaks can only be
found by removing it (not too difficult but a pain to do on a regular
basis). Same with the DVs and intercooler pipes. So I recommend that you get
rid of the crap Audi parts and replace them with good. The TBB can be
replaced with the APR bipipe (which I thoroughly recommend), and in doing so
you can check your intercooler pipes and make sure they are secure. The
Bosch DVs are prone to leaking, so replace them with Forge or Bailey's
(which may be slower, but reliability is more important). If you have the
APR bipipe then the Baileys fit better than the Forge.
Get a boost gauge. When you are familiar with what boost your car gives when
healthy, it 'may' help you see when there are problems.
Get VAG-COM. With this you can regularly check for DTCs which 'may' help
warn of problems.
Use the right engine oil (fully synthetic to VAG 503.01) and change it
regularly.
Observe proper warm up and cool-down procedures (the former is more
important than the latter).

Hope I've been of some help,
Dave

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Message: 2
From: "California Fields" <cfields72 at hotmail.com>
To: biturbos4 at audifans.com
Date: Tue, 03 Sep 2002 23:11:46 -0700
Subject: [BiturboS4] blown turbos

[ Converted text/html to text/plain ]

This may sound like a dumb question, but I'm curious how one would know if
one of the turbos is blown on the S4.  Would the lack of power be that
obvious? Any sounds or such that would easy to detect?

What about any leaks in the diverter valves, throttle body, or other parts?
------------------------------
Carter Fields - San Francisco
'01 santorin blue
stock (not for long!)