[Biturbos4] 2000 S4 Running Hot

Grant gfl1 at optonline.net
Mon Aug 29 22:34:34 EDT 2005

On Aug 29, 2005, at 10:00 PM, r harout wrote:

> so let me ask a question (nervoulsy)
> How likely is it that I was have catastrophic turbo
> failure if the car has only run with regular oil--but
> chnaged frequently?
Loaded question.  It *is* like death and taxes, but what you want to 
know is "will my turbos live to a ripe old age - say 100-125k miles".  

If good oil is used, and they always changed it, and never turned the 
car off when the turbos were hot, you're probably safe (and then a 
manufacturing defect will raise its ugly head and make me a liar).

The point of my post was that 1) these engines are actually quite tough 
- its just the turbos that fail, and 2) even turbo failure is more a 
matter of practicality than fate.  My service manager and dealer owner 
swear that they have low incidences of S4 turbo failure, and lots going 
long mileages.  Of course they are relatively young still.  Mine 
certainly didn;t show any signs of deterioration after 78k.

And I constantly read this - but mostly the audiworld S4 board, in 
which the same person asks chip questions and brags about their latest 
kill at 160mph  on the highway, and the next month is whining about a 
turbo failure.  I'm just guessing that maybe, just maybe, they push the 
car harder than average and occasionally show bad judgment.  But hey, 
that's me.

OTOH, I wouldn't buy one used unless I did know how it was treated, or 
unless I calculated the cost into my buying price.  $2500 off would 
basically let me self-insure happily.

Keman probably knows best, but I cant think of any way to test them. So 
good old common sense takes over for me.  90% of wear takes place when 
an engine is cold.  So dont drive it hard until the oil temp moves 
significantly.  And with turbos, most takes place when the hot engine, 
and sometimes red hot turbos (did I remind you that superheated exhaust 
gas drives a turbo??), shut down suddenly and the cooling flow of oil 
ceases.  It sits there, and cooks.  Or cokes.  Coke is crystalized 
carbon - pre diamond.  It is very abrasive, and, well, a crystal.  So 
it both clogs the oil feeds (like a fatty artery) and sandpapers the 
turbo bearings, which are VERY delicate.  Then bad things happen to 
your wallet pretty quickly.  The best advice is to let the car idle for 
30-90 after its run hard.  Note that there is an after-run pump that 
keeps water flowing through the turbo bearing, I dont know about oil.

When the engine is running normally, up to temperature, with oil 
flowing.  I'd posit that nothing is deteriorating any faster than 
glaciers (in the old days, before we started losing those too).

So dont fret.  Do warm up.  Do cool down.  do use good oil.  And do 
enjoy your car.

> Inevitable? What are the signs? I will use Mobil 1
> moving forward, but the owners before me did not.
> Maybe I should order the K04s now so I get them in
> time for failure!
> --- Grant <gfl1 at optonline.net> wrote:
>> Agreed.  Cool is actually not good.  The only
>> regular failures I know
>> of are turbo-related failures in which the oil
>> coked. Coking takes
>> place WAY above 200deg.  If you find differently,
>> please contact the
>> steel industry - they want your technology badly.
>> As to "how hot"?
>> the flash point for mobil1 is >400deg (F).
>> Admittedly, the hot underhood temperatures
>> contribute to this, but I'm
>> nto sure how much it improves things to extract the
>> heat to the
>> radiator, which then blows the heat through the
>> engine bay, which .....
>> So who's had a turbo failure that ran synthetic,
>> cooled down after hard
>> runs, and warmed up in the cold?
>> Anyone?
>> And who's had a ring job under ANY circumstances.
>> Anyone?
>> Grant
>> On Aug 29, 2005, at 2:53 PM, costco wrote:
>>> A lot of research has been performed with regards
>> to cylinder wear vs.
>>> coolant temperature in the 70's and 80's amongst
>> the automakers.
>>> 192 degrees F is actually optimal in most engines.
>> More or less is
>>> application specific. I would never put a 160
>> degree thermostat into an
>>> engine that prior had a 180 degree thermostat. In
>> many EFI systems that
>>> alone could cause the engine to run in open-loop
>> "warm up" mode,
>>> running
>>> excessively rich and ignoring the oxygen sensors
>> for short and long
>>> term
>>> fuel maps.
>>> I know the biturbos run 'hot' but IMO effort would
>> be better spent
>>> finding
>>> a way to get more hot air out of the engine bay
>> than trying to get the
>>> thermostat to open earlier. The biturbo RS4 has an
>> extended bellypan
>>> that
>>> covers some of the transmission-- this bellypan
>> section is obtainable
>>> from
>>> the dealer for around $120. It wouldn't take much
>> to get it to bolt up
>>> behind the stock bellypan, and I would definitely
>> give it a try as I
>>> wanted to before getting rid of my B5. I never got
>> around to doing it.
>>> The low pressure area there will probably greatly
>> help pull air through
>>> behind the front tires.
>>> If you have a little more money to toss around I'd
>> consider
>>> retrofitting
>>> the RS4 oil cooler into the system.
>>> Next I'd eliminate the foglights, elongate the
>> slits in the front
>>> wheelwells to promote more air through the
>> intercoolers, and replace
>>> some
>>> of the front lower center grill area with
>> something freer flowing yet
>>> would still provide some protection from rocks
>> hitting the a/c
>>> condenser.
>>> - Keman
>>> On Mon, 29 Aug 2005, Greg Amy wrote:
>>>> efficient. After all, we're not talking about
>> mid-60's
>>>> muscle cars here; these things run fine on 180F
>>>> thermostats.
>>>> GregA
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