This is done essentially by bolting a pair of turbochargers to the 6208cc AMG V8 to create 690bhp and 626lb ft of torque at 4300rpm.
The 'B63' conversion isn't as simple as that, though: Brabus also chucks in a chunky intercooling system, new air filters, a bespoke exhaust that includes high-performance catalytic converters, and a reprogrammed engine management system.
Perhaps the most innovative tweak, however, is that Brabus's engineers have fitted a left-turning turbo for the left bank of cylinders. This, Brabus informs us (for our engineering bent is not enough to allow us to understand such things properly), "allows the turbine and its inlet to be designed for perfect gas flow and gas dynamics", which basically means the engine is more responsive than would otherwise be the case. We think.