Originally Posted by
1967brutus
Inbetween steps: different props to see how the engine responds
An APC 9 x 6 brings the RPM up by 1100 to 12100 and gives a power increase from 0,4 to 0,44 hp
https://www.youtube.com/watch?v=MXgpKkJ9b5M
Going even lighter with APC 9 x 5 brings RPM to 13000 and raises power to 0.46 hp.
https://www.youtube.com/watch?v=B3vF1P6LQ_E
The 9 x 5 gives a slightly better static pull, but chances are, the 9 x 6 will perform better in the air. Remains to be determined.
It has all appearance that this engine was not even fully broken in (I have very little info on how much it has been run previously) but after several months of being shelved, I ran it for several hours in the past 2 weeks, now with the solenoid mixture control applied and first of all, fuel consumption has dropped VERY significantly (by about a factor 5, no joke) but what is more, over the course of that runtime, it gained about 850 RPM with the 9 x 5 (13850 RPM, appr 0,56 hp) and it does 12550 on the 9 x 6, or about 0,5 hp.
A plane build specifically for this engine is underway, but it most likely won't fly before spring next year.
I was highly surprised to see the engine gradually gain power, and it appears it has more of whatever it is people call "compression" in a Wankel.
But I have to do something about the muffler, because it is pretty restrictive. This engine responds apparently to inertia in the exhaust ducting. Simply extending the stock muffler with a random piece of silicone tbing resulted in a 300 RPM gain, repeatably.