Mechanical fan draws from the engine's power to spin the fan. Electric fan
draws from the battery to spin the fan. Only if the alternator/generator
requires the same amount of power to charge the battery does there achieve
no difference in power requirements.
Since alternators are typically more efficient than mechanical fans, it is a
net gain in power if you use an electric fan.
Even greater difference if you don't have an alternator/generator. On
Autocross cars that is possible if you want to charge the battery between
runs.
Joe
-----Original Message-----
From: fot-bounces+spitlist=cox.net@autox.team.net
[mailto:fot-bounces+spitlist=cox.net@autox.team.net] On Behalf Of John
Herrera
Sent: Sunday, June 29, 2008 3:12 PM
To: jim hearn; 'Friends of Triumph'
Subject: Re: [Fot] Trying to mount an electric fan on a high density
radiator
> I am trying to mount an electric pusher fan in lieu of the belt driven
fan>
to gain the hp.
I've always wondered how changing to an electric fan causes a gain in
horsepower. Or, to put it another way, decreases the loss of power used to
drive the fan.
Lets' say, for simplicity, that the electric fan and the belt-driven fan
move
the same amount of air. If the fans are equally efficient (maybe this is
where
I'm off base), then the same amount of power is used to drive them. The only
thing that has changed is that the power comes from your alternator instead
of
the crankshaft. But the alternator robs power from the crankshaft, so what
do
you gain? Also you have introduced a middleman into the sytem, which
increases
losses.
What am I missing?
John H.
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