Electric water pumps (was) alt charging cont sw

[Greg Hermann]

>-----Original Message-----
>From: steve ravet <steve.ravet at arm.com>
>To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
>Date: Sunday, March 14, 1999 11:32 AM
>Subject: Re: Electric water pumps (was) alt charging cont sw
>
>
>Think about how much motor/pump it takes to do 100 GPM....
>(I'm guageing this on the 180 GPM Stewartcomponents mentions
>at 9,000 rpm).
>You might need 10-15 at idle..
>Or am I missing something here
>Bruce

No, you are not. Looking at some pump curves here. A pump with a 2" D.
inlet and outlet, 5" D. impeller. at 1800 rpm,  will flow 80 GPM, make 20
feet of head, and use .66HP. Same pump at 3600 rpm will flow 150 GPM while
making 82 feet of head, and use 4.5 HP to do it. (All numbers are for
pumping H2O.) This is not too far off the size of a water pump for a SBC,
but prolly is a curve for a BUNCH more efficient pump design than what is
in a Chebby. But definitely good order of magnitude numbers for a pump in
this size range.

I have no desire to have a 3HP (min) electric motor hanging off of the
front of my engine to  drive the water pump!

Regards, Greg
>>
>>But, isn't it inefficient to spin all those things at engine RPM rather
>>than a constant RPM?  Seems like a pump/compressor that has to work over
>>a 10:1 input speed ratio wouldn't be as efficient as one designed to
>>work at a constant RPM.  Like A/C, and esp power steering.  If those
>>were designed to run w/electric drive at constant RPM maybe they'd be
>>more efficient.  Especially if you had a dual voltage alternator and ran
>>the accessories at 100V 3phase.  maybe?
>>--steve