Al,

What PL said and did is hearsay to me, as is all the other ~10 hp

anecdotes I've always heard. Your dyno data has to be a lot more

credible at least as far as it goes. Was the 48 gpm that was required

free flowing (no thermostat) from a cold reservoir through the engine

and back? Or was it closer to simulating actual conditions - hot water

in, hotter water out, operating at pretty much the temperatures you'd

expect in flight?

 

The 48 gpm @ 6000 was without thermostat installed, with a recirculating loop through a radiator much like actual conditions in the airplane; except that the lines and the rad were larger.  With the thermostat installed, the flow rate was 37 gpm; a significant drop due to the additional flow resistance.  The flow curves are shown on the dyno report - http://members.cox.net/alg3/Dynamometer%20test%20report.htm. The data points on the chart that are not connected are for the case of thermostat installed.

 

I am intuiting / speculating (key words here) that a pump that works

great at idle or in heavy traffic is going to be thrashing around

wasting a LOT of power at 6000 (or 7000) rpm through cavitation or

whatever.

 

I don’t think there is any evidence for that conclusion. Higher rpm simply translates to higher flow.  I’m sure there is a point where cavitation will occur, but the flow behavior was fairly linear with rpm all the way up to 7000 rpm.

 

Al