[Biturbos4] All causes to turbo failures known?

Keman keman at interwolf.net
Thu May 13 20:06:09 EDT 2004

I have heard that K04's without a chip and without exhaust produce basically
no performance gain, and if anything, less ... for the reasons you

Remember that the 2.7T is drive by wire, it has predictive throttle and all
sorts of methods to obtain boost and what we perceive as "throttle response"
... that goes into the toilet the moment you start talking about a turbo
that has even slightly more lag. It is adaptive though .. the system isn't
completely helpless .. still, if you have K04's, you should have a chip. :P

- Keman

> Larger compressor and turbine wheels imply higher inertia and poor
> spin-up times. Therefore you should see the turbo lag up to 3000 rpm
> (boost pressure is going to build up). Also, acceleration must slow
> down compared with K03, if ECU provides the same boost pressure and
> overboost value as before. Due to the higher inertia, the K04 type
> turbo charger is slower to spin up.
> The conclusion is with K04 you get a more robust turbo charger but the
> overall performance will degrade compared with K03. All with the
> assumption only the turbo charger has been replaced!
> Thus getting a K04 turbo charger makes only sense if you increase the
> boost level and adapt the corresponding system components (intake,
> boost, motor, exhaust).
> -Josef Hebenstreit

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