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So how can we reengineer an engine to lower the "lug"/resonant vibration? What kind of changes would need to be done? That's what i'm trying to figure out. (it's possible it's beyond the simplicity of having it worth doing and just down to selecting an engine with a low natural lug point too)
Thanks for the heads up of piston speed, that makes sense (although i'll note F1 engines have phenomenally high piston speed and are apparently 20% MORE efficient than our most efficient gasoline engines because the pistons are going away close enough to the speed of the flame front that it couples very nicely) so that means looking at undersquare engines and possibly modifying further could be interesting. Also possible that alternative fuels (producer gas/woodgas) with slower flame fronts might prefer a slower speed..?
By the way short rods long stroke might be worth considering too - the geometry near TDC means the short rod pulls it away more quickly, piston speed is not one speed but varies along with rod geometry. Long rods are often recommended for durability at higher speeds but it's possible a slow RPM torquer could be better served by short?
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