Rorac posted:

Real life engineering, smoothness is first and foremost about how balanced the engine is in operation. Inline engines are pretty inherently unsmooth, and inline 3's even more so because the forces the engine experiences are uneven. The only smooth inline is the 6. I mean theoretically so is an inline 8, but nobody uses those anymore. (This is why semi trucks use inline 6's, by the way, it's naturally balanced, and also has the smallest block mass and internal friction). V engines are generally smoother because they have more pistons, but an inline 6 is going to be smoother than a V6, because the V6 still has the unbalanced forces issue. So does a V8 really, but I4 is better than I3, and a V8 is better than a V6. You cannot have a fundamentally balanced engine below 6 cylinders unless you use something like a flat engine design.


This is all just the natural tendencies of the engine though. There are engineering tricks you can do, like adding a harmonic balancer, carefully picking and milling parts to be more precisely weighted against each other, etc, which would be equivalent to raising the quality slider.