In this article
Engine smoothness comes down to balance and how often the cylinders fire. Inline-six and V12 engines are naturally balanced, and a V12 fires more often per revolution than any common engine, which is why it has long been the choice of Rolls-Royce and Maybach. A cross-plane V8 is very well balanced and delivers effortless torque. But electric motors have no combustion pulses at all, delivering power silently and seamlessly — arguably the smoothest powertrain of all.
At a glance
| Engine | Natural balance | Power pulses per revolution | Typical use |
|---|---|---|---|
| Inline-four | Some vibration | 2 | Mainstream cars |
| Inline-six | Excellent | 3 | BMW, Mercedes S 500 |
| V8 (cross-plane) | Very good | 4 | American SUVs, S 580 |
| V12 | Excellent | 6 | Rolls-Royce, Maybach S 680 |
| Electric motor | No combustion pulses | Continuous | EQS, i7, Spectre |
Balance explained simply
Pistons speed up, slow down and change direction thousands of times per minute, creating forces that can shake an engine. In some layouts, the forces from different cylinders cancel each other out. An inline-six and a V12 (which is essentially two inline-sixes) cancel them very effectively.
Firing frequency
Each cylinder produces a power pulse when it fires. More cylinders firing more often means the pulses overlap, producing smoother, more continuous power. A V12 delivers overlapping pulses that feel like a turbine.
The V8
A cross-plane V8 — the type in the Escalade, Suburban and S 580 — is well balanced and produces lots of low-speed torque, so it rarely needs to work hard. Its distinctive burble is part of its appeal. Read S-Class engines explained.
Electric
Electric motors produce torque continuously with no combustion, and most EVs use a single gear, so there are no shifts. The challenge for engineers becomes other noises — road, wind and motor whine. Read active noise cancellation and the Rolls-Royce Spectre.
What passengers feel
In a chauffeured car, smoothness comes from the powertrain, the transmission, the suspension — and the chauffeur’s driving. Read what to expect from a professional chauffeur.
Good to know
Frequently asked questions
Why are V12 engines so smooth?
They are naturally balanced and fire six times per crankshaft revolution, producing overlapping power pulses.
Is an inline-six smoother than a V8?
An inline-six is perfectly balanced in primary and secondary forces; a cross-plane V8 is also very smooth but relies on crankshaft counterweights to achieve balance.
Are electric cars smoother than gas cars?
Generally yes, because electric motors deliver continuous torque without combustion pulses or gear changes.
