uhh montague?
while ringed engines are more tolorate of dusty conditions ringed engine put out more power and rpm than abc. let me explain why.
let's say that your piston on an abc engine is an inch from surface to the bottom of the skirt. that means that all that is rubbing on the side walls. on a ringed engine, the ring is in most rc cases, an eighth inch tall, so, using the one inch piston thing, you have one eighth the contact on a ringed engine and therefore have less friction and resistance resulting in more power. that extra power is usually put out in higher rpms. it is like going to a smaller prop. for instance, the os .46 fx and .50 sk ringed are made from the same materials, same case, same intenal parts, but the .50 is .04 cubic inches larger. it is also ringed. it produces 15% more power than the .46. that .04 ci isn't enough to justify all that gain in power. i have both engines. the .46 turns a 10x7 at the same rpm (give or take a few just because it isn't the same engine) as the .50 when turning an 11x7 prop