Thoughts on Engine Sound at High RPM's (kinda long)

jtsmith1

Not an expert in this area either, but I do believe almost any second or higher order vibrations can probably be neglected due to significantly lower magnitudes, cannot say this for sure though.

As far as the firing order, I never really put much thought into it. It seems that it would also be a function of RPM due to the change in momentum of the masses. I guess a good set of mounts (essentially dampers) and a properly balanced crank would be key here.

Not sure what you mean about non rotational unbalanced? The flywheel can essentially act as a bandaid, covering up some imbalances in the engine and absorbing some of those vibrations. Obviously, from a performance standpoint, we would like to reduce the mass of any rotational parts, but at what cost? I think a heavier flywheel would "overbalance" the engine, reducing any first order vibrations and probably minimizing any higher order vibrations as well.

Again, not an expert in vibrations, just have a basic undestanding. I do have some software on my laptop that we used in school to analyze engine parameters during design, such as balancing. If I knew every detail about the engine, such as bore, stroke, all the masses (major components such as wrist pins, piston, conrod, and crank), I could do a little analysis and see what sized flywheel provided the smoothest torque output and minimized vibrations. Question is, how much heavier would this be and what would the performance trade off be?