Re: <E28> Electric Fan .. any horspower gains?

[John Bolhuis <bolhuijo@xxxxxxxxxxxx>]

On Fri, 18 Oct 2002 kohlbren-m-d@domain.elided wrote:

> I don't know how much power you'll free up, but you should realize
> one potential cost of doing this.
>
> A thermostatically controlled electric fan will be binary -- on or off.
>
> The stock clutch driven fan is (as far as I understand it anyway...)
> controlled by a temperature sensitive device and essentially gives a
> continuously variable fan speed based upon actual cooling needs.

 I believe the viscous clutch on the typical belt driven cooling fan
is essentially binary in nature also.  They either are in lockup mode
when hot, or freewheeling when cooler.  There is a short time in
between as it tightens up or lets go, but I don't think that's part of
the intended operating zone.
 In my 325, the fan freewheels nearly all the time.  It only locks up
at a stop or at low speeds.  If you listen closely, you can hear the
extra "whoosh" when it is active.  The fan freewheels quickly after
the car is underway again since the air flow is more than adequate.
 Anyway, I'd guess that there are far better ways to spend money for a
BMW than another electric fan.

- --
 "It is an honor to be Cookie Monster."
   -Sesame Street spokeswoman Audrey Shapiro

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