had an enhanced engine. AMG redesigned the exhaust gas turbochargers and added new engine electronics. It produced 621 horsepower, pushing the car from in 4.2 seconds (0.2 seconds faster than the 2011 CL 63), with an electronically limited top speed of . The update also improved fuel economy and reduced carbon emissions by 3.5% over the outgoing model. "63" M157 5.5 L V8 Bi-Turbo The models listed below were powered by the M157 variant of the Mercedes-Benz M278 engine. Mercedes-AMG CLS 63 (W219) Mercedes-AMG E 63 (W212) Mercedes-AMG G 63 (W463) Mercedes-AMG GL 63 (X166 pre-facelift) Mercedes-AMG GLE 63 (W166 facelift) Mercedes-AMG GLS 63 (X166 facelift) Mercedes-AMG M 63 (W166 pre-facelift) Mercedes-AMG S 63 (W222 pre-facelift) Mercedes-AMG SL 63 (R231) Rumoured in 2009 and confirmed in 2010, AMG developed the M157, a 5.5-litre V8 with direct fuel injection and twin turbochargers. Power is rated at up to at 5,250-5,750rpm with a peak torque of made between 2,000rpm and 4,500rpm (the amount of power and torque depends on model, but these are the maximum ratings). Both engines are mated to Mercedes-Benz's 7-speed MCT transmission. Unlike the M156 naturally aspirated 6.2 L V8, which was developed entirely within AMG, the M157 is based upon the M278 used in the regular Mercedes-Benz S-Class and CL-Class. The M157 boasts 25% better fuel economy (10.5 litres per 100 kilometres versus 14.4 L/100 km in the European driving cycle) over the M156, meaning it avoids the US Gas Guzzler Tax for the first time ever, despite having up to 47 horsepower more. The M157's increased torque from both the regular version and performance package means the engine can be shifted into a taller gear sooner, keeping engine revs and fuel consumption to a minimum. The new M157 has an engine start/stop mode and is lightweight at 204 kg. The M157 is said to be ideal for powering full-size sedans such as the S-Class, but the older M156 remains in production, as its more precise throttle response is still well suited to smaller sportier models (the C-Class), until the 2015 model arrives, which is powered by a 4.0 liter V8. 5.5 L V8 BiTurbo models carry the "63" model designation, shared with the 6.2L V8 models. Visually, the 2011 S 63 AMG is differentiated from the 2010 model (itself face-lifted over the 2009 S 63) by the more angular design of the chromed dual exhaust tips, which