Here are a couple of pics of the newest Cyclon F2D combat engine I got. Seems like Alexsandr Kalmykov builds a new one every season. The last couple of years(PC-7, PC-8) have been world class. The Top15 looks world class. The case is a beautiful investment casting. The machining and piston/liner fit is top notch. The right hand side shows a good way to mount a muffler retainer. The muffler is a really tight fit, but will fall off in flight without a positive retainer. Just a piece of 1/16 in. music wire with some silicon fuel line on the loop that fits over the muffler. Another nice detail on the engine- the muffler outlet has a nice lip on it to help keep the retainer in place. Other thoughtful niceties- the prop driver, plug, and backplate all use a 3/8 in. wrench, so you don't need to go hunting for multiple tools to service the engine. A 3mm allen screw wrench for the mounting bolts, a 3/8in socket, and the head clamp wrench are all that is needed.(I really dislike the common method of a couple slots in the back plate for removal).
Initial runs look very promising. The two I've broken in seem to run on a par with the two AKM's I got a couple years ago. They do better with slightly shorter props, holding the rpm's in maneuvers better without sacrficing level flight speed. 29,000 rpm would do a good job in an ultrasonic cleaner though.
Great fun trying to do nice cloverleafs and RWO. Square eights are harder. I've already landed a couple times by accident.
Speaking of landing, the popular foam leading edge/rib construction on most F2D planes is a real bear for maintainence. It doesn't take much at all to punch a hole in the covering on landing. And on most the covering is not really glued down to the airframe, so the slightest fuel spill around the engine starts fuel leaking under the covering. I fuel-proofed a few by soaking all the likely seams for fuel to hit by pouring water-based urethane on and wiping the excess off. That seemed to help a lot.