<VV> Re: Adjustable Fan Pulleys--Need info

[James Davis]

As the 64 to 69 cooling fan is a centrifugal device, its power 
consumption goes up logarithmically with speed.  The fan is turned at 
1.5 times engine speed.  At 5,000 engine rpm (7,500  fan rpm) the fan 
draws 18 hp. At 3,330 engine rpm  (5,000 fan rpm), it draws 5.6 
hp.   So, dropping the fan speed from 1.5:1 to 1:1 would give you and 
additional 12.4 hp at 5,000 rpm.  Of course you cooling air volume 
would also be reduced commensurably.  You probably would not notice 
the difference at cruise but at the strip, well.....  A well 
lubricated fan belt works much better for short bast down the strip. 
Not that I would know that from experience. :-)
Jim Davis


>Where can I find testing numbers on this item OR can someone give me known
>facts about whether or not it can give a small HP gain?  It seems to me  that
>just reducing the fan's rpm fractionally would not make much of a  difference
>in drag via the fan belt.
>
>Thanks,
>Joe Dunlap
>Cen. Florida