The now-familiar engine has been reworked to produce 563 hp and 479 lb-ft of torque, a bit more than it delivers in other Mercedes AMG models. Impressively, the V-8, which has been modified enough to earn its own code-name (M159, in place of the regular 6.2's M156 designation), achieves this output without direct injection. As the successor to the 300SL Gullwing, the world's first direct-injected production car, this would have been a convenient time to fit the technology to AMG's V-8. But instead, AMG relied on more conventional tuner tactics to coax more power from its engine: a revised intake (with eight 11.4-inch by 2.0-inch velocity stacks), equal-length exhaust headers, and forged rather than cast pistons shave more than a pound off the reciprocating mass. The horsepower bump winds up being big enough to earn the M159 the crown of the world's most powerful normally aspirated production V-8.
And in fact, it's enough grunt to cause some problems at the other end of the driveshaft: for transmission durability reasons, the engine isn't permitted to produce full power in the first two gears. It seems that the Getrag-sourced dual-clutch transaxle - the same seven-speed unit found in the Ferrari California - isn't quite robust enough to deal with it all. The M159, like other 6.2s, is relatively soft below 4000 rpm, and coupled with the noticeable torque restriction in first gear, the SLS doesn't exactly explode off the line.
Mercedes claims that the SLS will race to 60 mph in 3.7 seconds (and continue to 197 mph), so you can imagine how brutally fast it is once the engine is allowed to run free. As in every other application, AMG's V-8 is the Tasmanian Devil of the automotive industry: snarling, popping, and barking while spinning up dust clouds and terrorizing anyone within earshot. The old-school, big-block mechanical cacophony coming through the firewall is no match for the guttural basso profundo exploding from the exhaust pipes - more satanic than melodic, it's impressive more by virtue of volume than pitch. It's completely insane.
It's also rather insane how small the cockpit is. Getting into the SLS isn't as difficult as you might expect - assuming you shook off the head injury and remembered to reach up and pull down the door before belting up - but once inside, space is at a premium. Legroom is granted by the power seats, but the seatback cants forward as the seat moves back, so tall drivers have to lean forward with their heads against the roof in order to have enough legroom to drive comfortably.