Mercedes Benz S550 .A new 429-hp 4.6-liter V-8 combines numerous advances and twin turbos to deliver noticeably more low-end torque. New rapid-multispark ignition can fire up to four times per millisecond, while high-pressure Direct Injection microscopically tunes the fuel spray to reduce 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