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John,
A gain of 40 hp is contingent on many factors and it may be possible on a
500+ HP engine or especially on those drag racing machines which on nitro
may put out over 2000 HP. In their case, where the run is over in a matter
of a few seconds, it may make sense to use an electric water pump. But
regardless of using electric or mechanical pump it takes the same amount of
power to flow the same volume of coolant at X GPM. Additionally, anytime
you convert energy from one form to another you lose some power since no
conversion is 100% efficient. So converting from mechanical to electrical
(via the alternator) and then back to mechanical (using an electric water
pump) is more of a loss than if you drove it with a mechanical pump to start
with. Again for short duration coolant situations, storing the energy in
battery and disengaging the mechanical pump will undoubtedly save some HP
that would have been used in driving the pump. The electrical pump can
circulate the coolant after the run to keep the engine from melting down,
but would be hopeless trying to provide the coolant flow necessary to keep
the block from melting - you would need a 2-4 HP electrical motor and if you
have ever seen one you know they are Huge! Almost as large as a Chevy v8
engine.
I can assure you that if auto engine manufactors could gain 40 HP or even
20 by converting from mechanical to electrical pump it would be done. This
topic comes up from time to time and gets addressed with more or less
vigor - but, in no case has it withstood the rigors of careful and
analytical scrutiny
So for short duration high power applications, an electric water pump can
circulate coolant well enough to cool the engine - after the run is
completed. However, I doubt if it would be up to the task of removing heat
adequate if the engine maintained an output anywhere near WOT.
So for long duration, high output situation (such as aircraft) the
mechanical coolant pump can't be beat. My 0.02 worth.
Ed Anderson
----- Original Message -----
From: "john" <frmrjohn@netonecom.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, September 29, 2002 2:47 PM
Subject: [FlyRotary] water pumps
> There is an article in hot rod mag this month that says an electric water
> pump has made gains of 40 hp, it states that it takes less power to run an
> alternator than a pump and units can be fabricated from universal units
from
> hot rod supply houses. JohnD
>
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