[LeifCarrotson]

Interesting that they use the mean of the absolute value instead of root-mean-square as in other sinusoidal applications (63.7% of the peak value vs. 70.7% for RMS).

RMS has all sorts of interesting properties, being directly proportional to effects that result from the square of the quantity being measured such as force on the connecting rods or acceleration of the piston, but mean piston speed is easier to calculate from familiar quantities to an automotive engineer like stroke and RPM. I wonder if engine longevity is actually proportional to mean piston speed or RPM, it would be easy to mistake the 7% difference given all the confounding factors...

[repsilat]

If they're only different by a constant factor, then both have the same interesting properties and neither is much more difficult to calculate than the other -- at least for sinusoids.

If something is proportional to one, it's naturally proportional to the other.

[uxp100]

Almost anyone on this website could answer better than me for this, was always weak in math, but I believe they differ by a constant factor for a sine, but for a more complex waveform they will not (well, the amount they vary by would be different for each waveform).

[lvh]

It's true that the factor between RMS vs peak-to-peak is different for e.g. a sine vs a sawtooth wave, but for other waveforms its still a constant (just a different one), and for this engine it should be just about a sine wave anyway.

[LeifCarrotson]

Circular motion about a crank produces a precise sinusoidal waveform.