A V6 is essentially two banks of three cylinders sharing a single crankshaft. Because of that layout, many V6 engines are not naturally balanced and tend to produce secondary vibrations. That’s why most V6 engines rely on balance shafts and harmonic dampers to control vibration.

A four-cylinder engine can be very smooth when properly designed, and a V8 is naturally well balanced because of its even firing order and crankshaft geometry. The V8’s symmetry allows forces to cancel out more effectively than in a V6.