Expected in November.
SL-Class Coupe/Roadster (on-sale: May 2012)
All-new 6th generation of iconic Mercedes-Benz roadster featuring all-new aluminum bodyshell, MAGIC VISION CONTROL, Frontbass sound system, power windscreen, ATTENTION ASSIST, PRE-SAFE, LED daytime running lights, electronic parking brake, standard panorama roof, ambient lighting and mbrace2. New optional equipment includes MAGIC SKY CONTROL, Hands Free Access, Active Lane Keeping & Blind Spot Assist, DISTRONIC PLUS with Pre-Safe Brake and PARKTRONIC with Active Parking Assist.
SL550: new direct-injection 4.6-liter biturbo V8 (429 hp, 516 lb.-ft) with ECO Start/Stop and more fuel-efficient 7-speed automatic transmission and 18" twin 5-spoke wheels. 0-60 in 4.5 seconds
SL63 AMG (July 2012): new 5.5-liter direct-injection biturbo AMG V8 (530 hp, 590 lb-ft) with ECO Start/Stop and AMG 7-speed MCT with 4 shift modes and RACESTART function. Standard AMG DRL's, twin-lamella grille, and trunk spoiler. Optional Performance Package yields 557hp, 664 lb-ft.
SL65 AMG (Nov 2012): high-performance 6.0-liter V12 model (621hp, 738lb-ft) now features 7-speed automatic transmission.
http://carscoop.blogspot.com/2012/06/mercedes-benz-usa-details-its-2013.html
Mercedes AMG twin turbo V12 changes - How the new M279 Twin Turbo V12 differs from the previous M275
You should all know by now that Mercedes is bringing back the twin turbo V12 with the new R231 SL65 AMG. We originally thought this was just the same old M275 V12 that had seen duty in the previous generation 600 and 65 AMG's but the motor has received some updates along with a new M279 engine designation. The 6.0 liter V12 to reach its new 630 horsepower rating received far more than just different ECU software.
A multi-spark ignition with twelve double ignition coils is used that Mercedes states provides for a smoother motor and more effective combustion. This also is used in conjunction with a new engine management system.
The cylinder heads were also revised in order to flow better for more power. The turbos have been changed featuring new wheels and are mated to new manifolds. The wastegate ducts have also been revised.
Additionally, the exhaust system underwent some significant changes. The catalytic converter system was optimized both for emissions and power. The wall thickness of the exhaust was reduced and the system is now 7 pounds lighter than the previous generation.
Other parts such as the intercooler, throttle body, and airbox remain the same. The M279 is a nice update to what already was a stout powerplant.
BenzBoost - Mercedes AMG twin turbo V12 changes - How the new M279 Twin Turbo V12 differs from the previous M275