Why does engine smoothness improve with a greater number of cylinders?

The improvement in engine smoothness with a greater number of cylinders is primarily due to the fact that the power impulses produced by each cylinder are spaced closer together. In an engine with more cylinders, each cylinder contributes to the power output at a more frequent interval. This results in a more continuous and even power delivery, which greatly reduces vibrations and the sensation of roughness that can occur when power strokes are spaced farther apart.

When an engine has fewer cylinders, the power strokes occur less frequently, leading to more noticeable gaps where no power is being generated, resulting in a rougher operation. By increasing the number of cylinders, the gaps between these power impulses diminish, allowing for a smoother operation overall.

While factors such as engine mass, RPM, and component wear can influence engine performance and durability, the fundamental reason for improved smoothness with more cylinders resides in the way power is delivered throughout the engine cycle.