I would take the ratings with a grain of salt. Unless you are comparing ratings of one engine to the next from the same manufacturer, or from an idependent like a magazine or something. Each company uses their own environment, dyno, fuel, data collection process, etc. Some optimize them beyond realistic conditions to yield higher numbers so even though Manufacturer A says 2.5 HP @ 40 zillion RPM and Manufacturer B says 1.3HP @ 37000 RPM doesn't necessarily mean engine A is better, just better in their test. You could put engine B in the same conditions and possibly get very similar or better results. Now when EXtreme RC or RC Car Action etc. does dyno testing, they use the same dyno for every engine so you can trust that data more. Ratings are really useful if you want to say compare an OS-12CZ to and OS-12TR because they are both done by OS on thier own dyno with their own process.