Michael Paauwe wrote:

Paul,
I realy don't know what flow rate the standard water pumps operate at but
don't think that they are at all eficient I would guess they are down around
5-10% efficient when the engine is at 6000RPM
The water pump has to circulate sufficient water to keep the engine cool at
idle and not over do things at full RPM.
I would guess that the electric version would not require anything like 3HP
to operate because it would be designed to operate at a fixed speed.
Perhaps you could dispense with mechanical thermostats and instead reduce
the speed of the electric water pump at idle or cruise conditions based on
the engine water outlet temp?
Just an Idea.

Mike

It always amazed me the rotary will cool in aircraft service. We are asking it
to cool at 150 continuous HP level when in car use it rarely sees more than 30 HP on
average. I think to reduce the capacity of the system below what it is
now by going to smaller lines and a low power water pump is foolish.
It takes a lot of water flow to get that amount of heat out of the engine and into
the rad. Jim Mederer at Racing Beat and Jeff Spitzer will agree with
me on this I think. As far as the rad goes we have more speed and potential 
airflow on our side. 

I don't agree the stock pump is so inefficient. On the contrary I think it
is over designed for car use. It probably could be a bit better but I also see
improvements in the later models. My guess on three HP may have been a bit high.
Looking in MacMaster Carr catalog I see well designed centrifugal pumps pumping 
35 gallons per minute with only one HP. The intake is 1-1/2 inch pipe size and 
the outlet is 1-1/4 inch pipe size which, as I recall, is bigger than the 
numbers would indicate.  

At 12 volts that would be only about 83 amps. Still an awful lot and more
than most alternators. Given a motor efficiency of 80% and 746 watts per HP.

You must realize those electric pumps were designed for drag racing when full
power is used for less than 10 seconds at a time. The rest of the time the 
engine is idling. Even the drag racers go to electric pumps to unload
the modest HP requirements of a mechanically driven water pump. 

In the Summit racing catalog one ad says the mechanical pump is
costing 15 to 20 HP and another ad claims their pump only draws
5.6 amps or .09 HP at 30 GPM. The rotating pump parts are probably
exactly the same or they could be. That is the closest thing I 
can think of to a 100 MPG carburetor. All this violates the laws
of physics and does not compute.

Paul Lamar
 
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