The SL550's M278 twin-turbo V8 is rated at 429 hp and 516 lb-ft and is praised for smooth, abundant torque. A recurring point of confusion is a sharp ticking noise on these gasoline-direct-injection engines; knowledgeable commenters explain it as normal high-pressure injector and valvetrain noise rather than a fault.
M278 4.6L twin-turbo V8 character and the 'typewriter' tick
Mercedes-Benz SL (R231) · mechanical