Unlike the last (frankly underpowered) S8, this new big-fast sedan is dropping the choked-off, Lamborghini-derived V10 in favor of a new twin-turbo V8. The good folks at Car and Driver are claiming the unit will displace 4.0-liters. Our source at Audi wouldn't confirm that displacement explicitly, but did say that C/D is, "on the right path." This same source noted that BMW's been using a smallish displacement twin-turbo V8 (4.4-liters) in the 7 Series for the past year and that Audi intends to stay competitive.
Our Audi source also noted that the new V8 will be offered in many flavors, and will allow Audi to meet all the emissions and mileage standards coming down the pike in the next five years. We're told to expect a wide range of configurations, similar to what Audi/Lamborghini did with their shared V10. That means different states of tune for different cars, as well as naturally aspirated and force inducted version. As for power, our source once again confirmed that Car and Driver knows what they're printing. Meaning that the 450 horsepower/450 pound-feet of torque neighborhood isn't a bad guess, though the final numbers could be higher.
Back to the car in the heavily cropped photograph (check out Autocar for the complete set of pics), we're still not 100-percent sure it's the S8. First of all, there are no visual cues to distinguish this black car from a regular A8, save for the requisite four tailpipes. However, as Autocar notes, the new S8 is said to have bold new bodywork to set it apart from the standard car. Also, examine the brakes. They appear to be larger diameter than the standard brakes, yet they aren't drilled or slotted. One would think (and we would agree with him) that an S vehicle would have a more serious set of stoppers. After all, even the A8 Hybrid "Concept" has fancier discs. Of course, maybe these are just placeholders used during cold weather testing. Yeah, we're pretty sure this is the new Audi S8.
[Sources: Autocar, Car and Driver]