Hello! After 4 years of math and analysis, I'm just now starting final design of a prototype of a new patent-pending engine design. The prototype will only be 50cc, and I see a lot of helpful information here, so I thought I'd join. Rod P.S. You can read a somewhat outdated description and see some equally outdated illustrations of my new engine at https://contest.techbriefs.com/2017/entries/aerospace-and-defense/8090 . The new baseline displaces 50cc with 8 cylinders, each completing 6 full cycles per revolution of the output shaft. I'm currently predicting it will be under 5" in diameter and 4" thick. It should produce on the order of 3.6 HP/7.2 lb-ft torque at 2626 RPM and be well over 50% efficient. It also employs Low Temperature Combustion (LTC) and should produce very little smoke and NOx.