[Biturbos4] 2000 S4 Running Hot

costco keman at interwolf.net
Mon Aug 29 14:53:28 EDT 2005

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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