I've been following this thread with some interest so I thought I'd add my
experience to it. I went to an electric fan setup on my TR7 and noticed a
real increase in the power output when I removed the standard fan.
What I attribute it to is the fact now the car rev's higher and thus more
RPM = more HP. So an 18% increase in this case would be easy to understand.
-jimb
80 TR7 F/I spider
74-1/2 TR6
>
>
> I spoke today with a fellow who is both car and aerodynamic-savvy. He
> explained that a crankshaft driven fan suffers from inefficiencies which
> become significantly worse than you might expect when operated at high
> speeds ( ie full throttle.) At lower speeds, the air moves over the fan
> blades in a fairly orderly and predictable manner. But as the RPMs increase
> the air is increasingly unable to follow the fan's contours and begins to
> show disorganized turbulence, which results in a great deal of energy being
> expended to overcome the resulting drag. The fan doesn't push more air, it
> merely stirs it around like crazy. Engineers have overcome this, to a
> degree by driving the fan via a belt at a speed significantly less than
> crankshaft RPM. They can increase the fan blade pitch for satisfactory low
> speed air moving performance, and make the blades somewhat flexible so the
> pitch 'flattens out' at higher speeds. I was told that 10-15 horsepower is
> a very realistic figure for the power to drive a crankshaft mounted fan at
> very high speeds.
> Having learned that, I apologize to anyone who may have been offended by
> my skepticism, shown below....
> Bob W.
## Jim Barbuscia SE Sun Microsystems Kirkland, WA. ##
## http://www.ptinet.net/~jimbar ##
## Standard Disclaimers apply (Jim.Barbuscia@Sun.COM) ##
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