On Sat, 26 Jan 2002, Alan & Debbie Lindner wrote:
> Hello Bob,
Hi.
> In an old email, you discussed bang for the buck.
> You had stated that:
> "get rid of some parasitic load by dumping the crank driven fan and
> replacing it with an electric fan."
Hmmm. THat sounds like something I might have said.
:-)
> What other benefits are there to going to an electric fan?
Well, there's the reduced drag on the engine. In most operating
conditions, the fan is not needed at all, so the drag is not justified.
Put in an electric fan with a thermostatic electrical switch and you only
get the fan under high load conditions or at idle/slow driving - e.g. when
you need it.
The crank driven fan can add dynamic imbalance of the motor... you don't
want that.
The combo of the first two elements really starts to matter about 5000
RPM's, so if you drive your car hard, you really do not want either of
these.
Also (I have no emprical data (yet)) the motor meems to spin more freely.
On my race car, I stab the gas and the motor spools to 4000 almost
instantly. But beside the electric fan, I also have a aluminium Tilton
flywheel and the reduced mass of that seems to help the motor spool up
more quickly.
> It seems my old fan works fine.....it turns when the engine turns. ;-)
Then use you crank driven fan. But if you're looking for real performance
gains, you cannot overlook the crank driven fan. Some dyno results show
the parasitic loss to be around 8 HP. For a Street Prepared SCCA
autocrosser - that's as much as 6% additional "free" horespower (assuming
a free-flow exhaust and some other minor tuning changes). That is nothing
to sneeze at.
For a prepared motor (cam, compression etc.), the benefit is that you can
leave the cooling fan on while the car is at rest to kool things down.
This helps keep the internal temps down...
> =========================
> Alan Lindner
> '72 TR6 French Blue set for racing
> CC75676L
> San Diego, CA
I'm putting an electric fan on my street car this year because I like it
on the race car so much.
Later,
rml
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