It's the end of the world as we know it. AMG, Mercedes' dedicated performance side-arm, will be announcing a new down-sized V8 at the upcoming Geneva show. Considering AMG has always been known for stuffing huge engines in pimped out Mercs, the prospect of a smaller, more efficient AMG engine is a bit hard to stomach at first. But read a little deeper, and you get the feeling it'll be alright - they're bolting a set of twin turbos up to it to make up for the drop in displacement, and both power and efficiency are going up.
The M157 V8 is being de-stroked from a massive 6.2L down to "only" 5.5L, but is gaining a pair of exhaust-driven huffers, direct fuel injection (an AMG first) which allows a rather high 10.0:1 compression ratio, and a bag full of new tricks to make it both faster and a little greener. It will first be introduced in the full-size S63 AMG sedan (which will oddly keep the "63" moniker despite being nowhere close to 6.3L) later this year, with trickle-down to other V8 AMG models expected over the next few years. Other cool tidbits include an aluminum crankcase, an air-to-water intercooler(!), and an alternator that only charges during deceleration to reduce parasitic drag.
Initial numbers are pretty promising. The basic-spec M157 makes 544bhp @ 5500rpm and 586 lb-ft of torque between 2000-4500rpm, with an optional performance package boosting those numbers up to 571bhp and an epic 660lb-ft (894nM) of torque. The S63 also inherits the new 7-speed Speedshift MCT, seen in the SL63 and E63 AMG already - which uses a wet multi-plate clutch setup instead of a traditional torque converter for faster shifts and increased efficiency.
With the basic motor the S63 will run up to an electronically limited 155mph, and with the optional performance pack it'll do a rather insane 186mph - that seems like more than enough for an S-class, I'd say. 0-100km/h takes 4.5 seconds, or 4.4 with the performance package - seriously quick times for a massive full-size luxobarge.
What's really neat is that AMG claims the new biturbo V8 will be more efficient than the outgoing 6.2L unit by nearly 25%, meaning it will skirt around the US gas-guzzler tax for the first time in ever - despite having up to 47 horsepower more than the outgoing model. The new M157 will have an engine start/stop mode to waste less gas sitting still, which can't hurt. Mercedes will be showing a track-prepped S63 AMG in classic racing livery at Geneva alongside a classic 1971 300SEL 6.9 that took second overall at Spa-Francorchamps that year thanks to AMG preparation - and a 428bhp 6.8L V8, of course. Expect to see more pictures and get more details when the Geneva show finally rolls around.