I’ve driven Mercedes’ new shape-shifting V8 engine, and it’s blown my mind

Mercedes-AMG turned to hybrid four-cylinder power in response to tightening emissions regulations, but the market didn’t respond well. As a result, the C63 is now no more and AMG is increasing the cylinder count in a move that goes completely against the market trend, introducing new six-cylinder engines and a brand new V8 to its lineup. 

AMG has been known for its lumpy, rich, cross-plane crank V8 sound for decades, and no matter how hard synthesised sounds try, four-cylinder 63 models are never going to be able to replicate it. That’s why Mercedes has made a complete U-turn in developing the M177 Evo, a new 4-litre twin-turbocharged V8 that makes its debut in the new S-class and will also feature in a number of AMG products such as the new CLE and E63 models.

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What makes this new V8 so special is that unlike the older 4-litre cross-plane crank V8 this new power unit uses its flat-plane crankshaft technology (normally the preserve of more exotic supercars) to meet Euro 7 emissions legislation. Key benefits include lighter construction, quicker throttle response and improved exhaust scavenging that improves efficiency. There is usually a trade-off for such a configuration and that’s the loss of the trademark cross-plane crank AMG sound. Except in the case of the M177 Evo…

Listen closely to the new V8-engined S580 S-class on startup and you can hear that lumpy AMG sound we all love, which doesn’t seem possible, and ordinarily it wouldn’t be. Mercedes has thrown all of its engineering might into this engine though, creating an ingenious solution to the sound dilemma that doesn’t involve cringeworthy external speaker systems and synthesised sounds. The internals of this V8 have been developed specifically to sacrifice some efficiency in exchange for a sound just like those old V8s.

The M177 Evo features a special exhaust crankshaft mounted to a magnetic actuator, which is designed to offset its position at startup and below 3000rpm purely to replicate the uneven exhaust flow of a crossplane crank engine. At higher revs, the crankshaft will switch back to its typical flat-plane crank position to take advantage of the efficiency benefits, and extract 530bhp in the case of the S-class. Aero within the engine has also seen attention, with a spoiler within the intake valve channels directing flow around the cylinder chamber to create swirl – combined with the use of the Miller Cycle (the first in any Mercedes V8), this improves the efficiency of the burn.

Driving the new Mercedes M177 Evo V8

That AMG sound gently permeates the cabin of even the ultra-refined S580, acting as a constant reminder of what lies under the bonnet ahead. Models in which the V8 is designed to provide more theatre will really take advantage of all of this clever engineering with more volume inside and out, but the fact it’s present at all in a non-AMG S-class is a good sign. And on the road it feels and sounds authentic, with a distinctive character that matches an impressive response. There are times when I had to remind myself I was driving Mercedes’ limo and not AMG’s latest supersaloon. 

The S580 is a mild-hybrid just like virtually every other Mercedes-Benz and AMG product on sale today, which is handy. Flat-plane crankshaft engines inherently produce less torque than their cross-plane crank counterparts due to a shorter stroke, but hybrid assistance plugs that gap. Power delivery is as effortless right from the bottom of the rev range as expected, with a 553lb ft torque figure more than enough for this 2.2 ton saloon. In something smaller and lighter I think this engine will make amends for past missteps. 

Of course, throttle mapping in an S-class is completely different to how it will be in an AMG product, and so it’s measured and relaxed here in every one of the drive modes. Engine response is still excellent, with a linear delivery right through to the redline making it a pleasure to rev out regardless of how unnatural this feels in an S-class. When you do pass 3000rpm, the transition between the sound-focused camshaft and efficiency profiles is imperceptible, the only indication is the change in tone to a more even flat-plane crank sound, but you have to be actively listening to notice it.

We won’t receive the V8 engined S-class in the UK, but my drive in the S580 provides insight into what we can expect when AMG’s new-generation of V8 models finally reach the UK. 

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