Re: Why r there different max rpm ranges?
Any internal combustion piston engine, whether 2 or 4 stroke develops different power over different rpm ranges. Some engines need higher rpm to make their rated power, others max out at a lower rpm. Port timing or valve timing and size, ignition timing, bore and stroke, connecting rod length and other engine specs modify the rpm at which max hp and torque occur. The term lugging an engine means that either the load or the gearing/prop are not letting the engine achieve its max rated rpm.<br /><br />Engines run out of power at some max rpm because they run out of breath. Just about any engine can be modified (not always a good idea) to make more hp by helping it breathe at a higher rpm. However, concomitant improvements in strength and engine balance may be necessary to withstand the higher rpm. If you put a race camshaft in your car engine it might rev to a higher rpm and make more power, but if you don't put stronger valve springs on it you may bust a valve.
