RE: Changing 5KT afterrun fan time limit

[Aleksander Mierzwa <alex@matrix.pl>]

Andrew wrote:

	>Minor nit:
	>
	>The afterrun fan is not triggered by coolant temperature, but
	>by a separate under-hood sensor that mesaures the air temperature
	>inside the engine bay.
	>
	>The fan's purpose is not to cool the engine, but to cool the engine
	>bay so the wires, belts, plugs, etc. don't cook.

I was referring to the afterrun operation of the _radiator_ fan, not the
_injector_ fan. Take note that we are talking about turbocharged Audis here.
On turbo cars the afterrun operation of the radiator fan is mainly intended
to cool the turbocharger bearings - that's why it is triggered by a coolant
temp switch and that's why the system incorporates auxillary electric
coolant pump to force coolant circulation after the engine has been shut
off. It does cool the engine bay as well - however, there's a separate
injector cooling fan triggered by an air temperature sensor that cools
injectors and stuff. On non-turbo cars, which neither have an electric
coolant pump nor injector fan, I agree - the afterrun operation of the
radiator fan is mainly to reduce underhood temp and to prevent excessive
pressure buildup in the radiator.

Aleksander Mierzwa
Warsaw, Poland
mailto:alex@matrix.pl
87 Audi 5000CS turbo (mine)
88 Renault Medallion wagon (mom's)
91 mountain bike (just in case both cars broke at the same time :-)