Al,

I made a quick analysis from facts obtained elsewhere.  I surmised that PL was right about the 10 hp at high rpm because I've heard that number from so many sources over the years.  How considerably off do you think PL was and why?

Jim;

I don’t know that Paul was off, I was just agreeing with Dale that he may have been. I found in my notes that the estimated (stock) pump power at 6000 rpm was about 2.5 - 3 hp, so the 10 seems too high; but I can not find any data in my file to back it up. Paul did set up a test loop and do measurements – I don’t have the results. Bill Jepson provided flow and pressure drop data which could be translated to power.

 If it is 3 hp, one might expect similar power required for EWP pump drive to produce the same flow rate (power to generate the current not included); however I expect the EWP pump efficiency to be higher because it seems apparent looking at the stock pump impeller that not much effort was made for high efficiency.  Until someone does consistent flow rate – power data for both pumps, we don’t know.  Did PL ever do that?

On the dyno test, I measured 48 gpm at 6000 rpm for the pump on my 20B, (which is interesting that it is close to Jack’s data point of 3 hp pumping 52 gpm)  but the external loop was likely lower pressure drop than rads on my airplane.

Al