I will be very interested in your Craig-Davies experiment.  It seems to me that this flow rate is very marginal.  I had considered using a single Mezirie WP336, but thought having two pumps for redundency would be preferable.  Earlier I tested the unrestricted flow rate for one of these pumps at 16 GPM using cold water.  The only way it could meet specifications would be to see an increase in flow at higher temperatures.

Thanks for the good info Bob.  Those flow rates do seem kinda low, but not necessarily too low.  IIRC, Todd was getting about 9 gpm with a single Davies Craig pump, and was doing just fine on temps.  You would have considerably more than that with two pumps, and less with a single.   If you run the pumps in series, you can probably use the second one only for climb and maybe really hot days in cruise.  

Keep in mind that no one has proven any flow rate that's required for our engines.  There are lots of charts, and numbers floating around, but none of it really means much to me, because there are too many variables.  Ernest said that I hadn't proven mine in flight, and he's right.  That's what counts, and we would all do well to remember that.   Nevertheless, I can't help but want to test the flow rates of the two pumps, though any flow rates that I get will not prove that either will work, but it will show which pump flows the most water in a similar test. 

Cheers,

Rusty (new flowmeter ordered)