Just to put this water pump thing in everyday real world context for people
I did a few calculations.

To load an RX7 engine down with 150 HP continuously given the 30 HP necessary
to get just the car down the road at 60 MPH or 88 FPS
will take a trailer.

Total HP in terms of pounds ft per second is 150 * 550 
or 82500 pound FPS therefore at 88 FPS the total drag 
would be 937 pounds.

The drag of the car alone at 88 FPS is (30 * 550)/88 = 187 pounds.
Net drag of the trailer needed is therefore 937 - 187 = 750 pounds.

Cd is the drag factor. Assume one for a simple box trailer.
FA = Frontal Area (height times width) of the trailer. At this point unknown.
It is what we are looking for.

.0026 is the air density factor based on MPH.

Drag = Cd * FA * MPH^2 * .0026
For a Cd  of one for a square box and doing the algebra;

750/(MPH^2 * .0026) = FA 
750/(60^2 * .0026) = 80 square feet.

Given a six foot wide trailer it must be about 13 feet high
and be towed far enough in back of the RX7 so it gets full
blast of air. A eight foot wide trailer would be only ten feet 
high. This assumes the trailer weighs nothing
and no hills are climbed. That is a pretty big trailer.
More like a motor home.

It amazes me the stock RX7 water pump and cooling system
passages in the block will do this. I don't think the stock
rad would be up to it at 60 MPH however.

At 200 HP of course everything gets worse.

Averaging 200 MPH in a 300 mile cross country race will tax the cooling
system and it will be interesting to see what works. Hopefully
we will have rotary engine powered entries in the coming Oct. Apple Valley 
to Copper State race and find out.

Paul Lamar
 
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