The 429-hp 4.6-liter V-8 in the SL550 combines numerous advances and twin turbos to deliver 12% more power. Its 516 lb-ft torque peak offers 45% more thrust at just 2,000 rpm. New rapid-multispark ignition can fire up to four times per millisecond, while high-pressure Direct Injection can microscopically fine-tune fuel spray in just 0.1 milliseconds, reducing emissions, fuel consumption and noise. A lightweight diecast-alloy block, quicker and more widely variable valve timing, reduced friction, and clever "on-demand" ancillary components like the alternator further boost efficiency.
A fuel-saving new ECO Start/Stop system automatically shuts off the engine at stoplights and other idle situations. As soon as the driver lifts off the brake, the engine instantly restarts, for immediate acceleration response. The ECO Start/Stop system can also be shut off by the driver at any time.
Electrically heated seats quickly take the chill out of even the coldest day. Three levels of warming automatically step down after several minutes to the lowest setting.