I ran across this old chart I had of pressure drop through
a V8 engine as a function of coolant flow rate from KS Racing
Products.

At 40 gallons per minute it was 10 psi and linear from
there down to 0 psi and 0 GPM. 
Uwards it looks like this:

GPM  psi
50    14
60    25
70    55

Lets look at 40 GPM and 10 psi.

One foot of water at 8 pounds per gallon or 64 pounds per cubic foot
is .444 psi. So ten psi is a head of 22.5 feet of water.
40 GPM is 320 pounds per minute times a head of 22.7 feet is
7207 pound/feet per minute HP. 

That is 120 pound/feet per second or about .218 HP at 550 
pound/feet per second for one HP.

Given the pumps are only about 50 percent efficient the peak 
input pump HP would then be around .43 HP. This is the pressure drop
for a large V8 so the Mazda 13B should be somewhat less. I will
add another pressure gage at the coolant input to the block on my
13B turbo engine to obtain some real world pressure drop numbers
through the block.

Obviously claims of saving 13 to 20  HP with electric pumps are 
way out to lunch. Even at five times the pressure drop and
double the flow rate the HP consumption would be 5 HP
max. Furthermore the V belt driving the pump  would probably
slip at this HP level or below this HP level.

Paul Lamar
 
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