[Biturbos4] Turbo reliability

[j y]

Abt (Audi tuner in Europe - officially recognized by Audi) also sells a KO4/K03 hybrid that has received favorable reviews. If I go the hybrid route - I might go with them. If I go straight K04s - then I will buy the KKK turbos and use GIAC or REVO software. I will tweak them using lemmiwinks like I am doing with my current set-up. 

Quincy Chiang <b5quattro at shaw.ca> wrote:I just read that and wonders the same thing. As far as successful K03 alternatives for our S4, there are:

- straight K04
- K03/K04 hybrid
- K03/K16 hybrid
- K04/K16 hybrid

Personally I don't quite trust how the hybrids are made, and there have been a few failures on AW. I don't the whole story, but I would trust the factory pumping out K04s versus some small company rebuilding busted K03 turbos.

Quincy

----- Original Message -----
From: j y 
Date: Tuesday, August 30, 2005 4:53 pm
Subject: Re: [Biturbos4] Turbo reliability

> hmmm....I wonder if Keman still believes that K04s are not a 
> satisfactory replacement (my words) for K03s. So far, no other 
> turbos have been introduced other than K03/K04 hybrids that fit 
> into the S4 engine bay and provide the same performance. There 
> have been attempts by vendors to "one-up" the K04 - the stories on 
> AudiWorld - but so far - no real world sucess stories.
> 
> 
> 
> Ti Kan wrote:
> Below is a post from Keman from a while back on turbo failure that's
> good reading for the new members of the list, and a good review for
> the rest.
> 
> -Ti
> 
> > What kind of failure?
> > 
> > >> 1) Wear
> > 
> > With infrequent oilchanges and poor quality oil, a turbos 
> bearings can
> > certainly wear out. They don't have to, Gerret for example will 
> tell you
> > that their turbos will outlast any engine you attach them to so 
> long as
> > nothing breaks that controls the turbo.
> > 
> > >> 2) Boost leak causes over-spinning of the turbo -> rpm to 
> high ->
> > >> mechanical breakdown
> > 
> > IMO there's your #1 cause. I highly recommend a good boost gauge 
> .. I've had
> > one since 10k miles, even though my S4 still isn't chipped.
> > 
> > >> 3) Defect or mal-functioning air-mass gauge causes ECU to 
> read out
> > >> lower values for the air-mass flow -> ECU responses with 
> lower fuel
> > >> injection -> lean fuel-air ratio -> high temperature on 
> turbine of
> > >> the turbo -> thermal breakdown
> > 
> > The O2 sensors detect this though and that's how you know the 
> MAF is gone,
> > there are codes for reaching the adaptive limit rich set and a 
> quick glance
> > at the MAF under heavy throttle shows much less grams/second 
> measured than
> > what is really coming in.
> > 
> > >> 4) Dump valve or bypass valve
> > 
> > When the bypass valves fail, they can cause an invisible boost 
> leak since it
> > can dump air back in front of the turbo, but still behind the 
> MAF sensor.
> > Aftermarket valves are a good idea.
> > 
> > The wastegate diaphram can rupture, overspinning the turbo. 
> Rare, but
> > nothing is impossible. I've seen it once.
> > 
> > >> 5) Insufficient oil supply for the turbo - oil lines clogged or
> > >> leaking
> > 
> > Crappy oil and infrequent changes, sure.
> > 
> > >> Normally the third case shouldn't be possible due to
> > >> exhaust-gas-temperature sensor sitting between turbo and lambda
> > >> sensor. ECU should detect high temperature (not only peak but 
> also> >> average value) and protect the turbo using the waste gate 
> and/or> >> switching over to limp program.
> > >>
> > >> What year of manufacture of the S4 has this exhaust-gas-
> temperature> >> sensor?
> > 
> > All biturbo S4's have two EGT sensors, one for each side just 
> inches after
> > the turbo outlet.
> > 
> > >> Is a K04-type turbo charger a solution to cope with the 
> mechanical> >> and thermal breakdown, independent whether the car 
> is tuned or not?
> > 
> > I honestly don't like the K04's. They're just a K03 housing with 
> a different
> > turbine wheel. I've compared them side by side now. There are some
> > ballbearing alternative turbos going around now that fit our 
> cars which are
> > a much more appropriate design and are more efficient. If you're 
> going> through the hassle of replacing the turbos, you might as 
> well go with
> > something else.
> > 
> > >> To you think the air-mass gauge is a problematic sensor? Do 
> you have
> > >> a remedy?
> > 
> > It's problematic more often than not, but you'll get a check 
> engine light
> > before it becomes a serious issue.
> > 
> > - Keman
> 
> 
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