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David, Tend to agree with the tip speed comment, unless the reduction drive is going to be too large or too heavy. 2.6 : 1 fits pretty well and a prop of 72" loa works pretty well also. Of course the turbo or supercharger throws a wrench into everything. If your engine can take it you can size the TC or SC to work with your tip speed. If it is overspeeding or stalling (cavitating) just add a few blades! The rotary is tough, and with the ceramic seals you can dial-your-hp. Bill
Bill, I guess you are right about peak power RPM. I have been thinking about turbo, p-port, and highly tuned applications where the torque curve does not drop off as fast. Looks like typical n.a. does indeed peek around 6000-6500RPM.
I still maintain that Max RPM should be determined by prop tip speed. Of course, one could always adjust prop length so that redline lands at a desired RPM.
Dave Leonard
Dave Leonard
On the dyno you will know better, but on the 4 port (stock) you should see peak power at less than 7k. On the small port version of Powersport’s p-port with a similar intake length they were seeing best power at about 6,500. They may have been slightly over-proped. I would expect a similar max power with standard side ports. Or possibly even lower rpm. Bill Hi guys
I’m wanting to inflight test for the best RPM for peak power of our 4 port Renesis with variable pitch prop (No constant speed control at present).
On Takeoff at Full Fine we hit 6900 after a few seconds and then rpm builds to 7400 by 500 feet and 110 KIAS
I’m wondering if we are well past the peak torque and would be better off at a lower rpm.
Am I right in thinking the following would use the aircraft as a Dyno to establish rpm for best power?
1. Set up level flight (auto pilot)
2. Maintain WOT and constant mixture (best power - say 0.9 Lambda - 13.2 AFR) via Wideband O2
3. Vary RPM in 200rpm increments for 2 minutes each setting between 5600 and 7200 by adjusting prop pitch
4. Note Fuel Flow and IAS (Logged on Dynon Skyview)
I’m thinking this would give me an indication of best RPM for highest power.
Our Inlet is just under 19” long, measured from the side face of the engine.
So I’m thinking peak torque may be around 6400 rpm.
Your insight would be appreciated.
Thanks
Steve Izett
Renesis 4 port RD1C (2.85:1) Inflight Adjustable Prop
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