Here are the specifications:
These are some solid specifications. Boost pressure from the twin turbos is 17.4 psi. At the 10.5:1 compression ratio there should be some room to increase boost even on pump gas. There likely will be a power kit from Mercedes themselves. They also left themselves room for a Black Series variant as AMG is not going to play second fiddle to Porsche. That model will also be prepared to go up against the Ferrari 458 Italia when it gets boosted.
The stroke at 92.0mm exceeds the bore of 83.0mm for an undersquare design. Mercedes did not go out of their way to make this rev but it looks like they are using a long stroke to mitigate torque loss from the lowered displacement. It still revs to 7200 rpm which certainly is decent in the direct injection boosted V8 era but it obviously is no M159.
479 lb-ft of torque is good but not great. Once again, AMG is leaving themselves room here as there is no reason they could not match the 516 lb-ft Audi gets from the same displacement.
The engine features a dry-sump oiling system so no skimping here by AMG. It will stay lubricated under high cornering forces. The cylinder bores are lined to decrease friction. The pistons are lightweight aluminum and forged for strength.
As reported first by BenzBoost, the turbos are top mount and located between the cylinders matching Audi's 4.0 TFSI layout and BMW's S63 4.4 liter twin turbo V8.
Those of you who were worried about the loss of displacement compared to the M157 should not be. This is a hell of a motor with a compact design that offers plenty of headroom.