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

corvairs lonwall at corvairunderground.com
Fri Nov 11 20:19:14 EST 2005


Jim - One of the factors that has been overlooked on these incremental 
pullies is that the belt length has to change with each ratio setting. 
Originally the incremental pullies were sold with (I believe) 4 
different belts, depending on which ratio you chose to use. This is 
backround information only and not directly related to the rpm/hp issue 
- althoough if you lose your belt because it's the wrong length then you 
will lose considerable hp ............Lon

www.corvairunderground.com

James Davis wrote:

> 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
>
>
>
>
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