Message text written by Mark Hooper
>I read on the list that the fan consumes up to 8 Hp. If so then switching
to
an electric fan would seem to be one of the single largest increases you
could do without radically changing the engine's functioning.
Question. That 8 Hp is only while standing still, right? I mean at highway
speed, the wind coming through the nose of the car should reduce the fan
drag to nothing. Or does it?
<
Er, no (cue the big argument. Again), Mark, the fan is sized to provide
adequate cooling at idle speeds and is way oversized at higher speeds. The
power required to drive the fan increases with engine speed. In fact it
increases with the cube of the speed and at red line it can draw as much as
8 (some estimates are as high as 14) HP. I think the wimpy fans installed
in our TR's are quite a bit less than that.
But the beauty of an electric fan is that it can run at full capacity at
idle and switch off when under way.
You are right that the induced air flow through the radiator will help the
fan out but air flow is a function of engine speed. At high revs in low
gears the induced air flow is minimal. If you are coasting down a hill in
neutral the wind will help turn the fan but most of the time the fan will
pull more air than is forced through the radiator by forward movement.
Dave
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