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Hi Steve,

The torque curve for the rotary is fairly flat up into the 8000+ RPM range. So in general, HP will continue to go up with RPM until destruction of the bearings around 1100 is a number I have seen floated around for stock rotors. The prop will start becoming very inefficient as the tips go supersonic.

That means, you calculate your RPM for supersonic tip speed, and that will be best power/redline limit.

Peak efficiency is a different story.

Dave Leonard

On Thu, Aug 6, 2020 at 7:59 AM Stephen Izett stephen.izett@gmail.com <flyrotary@lancaironline.net> wrote:

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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