For the EWP's we're trying, I agree, but they do make larger EWP's.   At the same time, I think most of us can agree that the stock pump flows too much for what we're doing.  Why would anyone slow it down by changing pulleys if it really needed to be flowing that much.  <snip>

Rusty
 
Ok Rusty, Lets be clear here, the reason to run an underdrive pulley isn't to reduce FLOW. The reason is to prevent CAVITATION. This is dramatically different than trying to reduce flow. The max output of the stock pump is about 53gpm at 7000 RPM. (Info supplied by the designer of PowerSport's PSRU) Once driven into cavitation the same power is required to produce LESS flow. If you run your engine at speeds that will get the stock pump close to cavitation you need to slow the pump to prevent simply wasting power. In the Meizere catalog they have a chart for a EDWP they make showing the curves for HP consumed to produce a specific pressure and GPM. When talking to Steve Wienzerl (Powersport designer) he suggested that they would like to see as much as 60 GPM! According to the Meizere chart this would require 3.5 HP+.
 I am receptive to the possibility that a lower flow rate could provide adequate cooling by means of a higher delta T. I am bothered by the fact that the rotary as configured by Mazda is a series flow engine, flowing front to rear and thereby cooling the front rotor better. Everett Hatch did considerable experiments with replumbing the cooling system to even the heat extraction. I don't see how the EWP could do anything but make this situation worse. Many people are now touting the HP savings by using the EWP. Since you are using the EWP as a backup (which seems a sound idea) you aren't sure it will do the whole job. Todd's seems to work OK. The fact that a 0.1 HP pump could replace a 3.5 HP pump to do the same job does seem counterintuitive to say the very least. I am not a nay-sayer (ah la Lamar) but I have the engineer's disease of needing to know WHY something works so I won't screw it up when I put it in my system. I cannot rationally believe that a 9 GPM pump can replace the 50+ GPM pump at max power! I thank everyone doing the flow experiments to help us understand the system. I don't know if Alan Tolle monitors the Fly Rotary archive, but I am curious if Everett ever experimented with EWP's?
Bill Jepson (Still skeptical, But willing to listen.)