Mercedes-Benz’s latest S-Class is making waves, not just for keeping the flagship sedan alive in an SUV-dominated market, but for an unusual technical detail: a flat-plane V8 engine. This decision is striking because such engines are typically reserved for high-performance supercars, not luxury flagships.
The Oddity of a Flat-Plane in a Luxury Sedan
Traditionally, V8 engines have used a cross-plane crankshaft, known for its smooth rumble. The S-Class’s flat-plane configuration is rare for a luxury vehicle due to its inherent mechanical drawbacks. While simpler in design, flat-plane V8s generate intense vibrations – the same type found in four-cylinder engines – because of the way their pistons move.
These vibrations aren’t ideal for a luxury sedan, where refinement is key. Counteracting them requires engineering compromises like balance shafts, and even then, noise and harshness can be issues, especially in larger engines. The Corvette Z06’s 5.5-liter flat-plane V8 was praised for pushing the limits of this design, but it’s a testament to how challenging it is.
Why Flat-Plane Engines Exist
Flat-plane V8s are typically favored in supercars for their lighter weight, quicker response, and higher revving capability. They don’t inherently produce less low-end torque; that’s more about engine size. However, a cross-plane V8 is simpler to smooth out, making it better suited for larger displacements and luxury applications. The previous S-Class model used a cross-plane V8 for these reasons.
Possible Explanations and Future Implications
Mercedes hasn’t revealed the exact rationale behind this choice. It is possible this is simply a result of production consolidation, meaning all future Mercedes V8s could adopt the flat-plane configuration. This could even lead to more unorthodox combinations, like a flat-plane V8 in a G-Wagen.
Mercedes claims the new engine offers “exceptional smoothness,” suggesting they’ve overcome the inherent vibration issues. Whether through advanced engineering or new technologies remains to be seen.
The inclusion of a flat-plane V8 in the S-Class is unexpected but intriguing. It will be crucial to see how Mercedes manages the vibrations in real-world driving conditions. This shift could redefine what performance means in a luxury sedan, and it will be interesting to follow if this design choice becomes more widespread.
