2012 Mercedes Benz SLK55 AMG to Hit Frankfurt With 422 HP V8

Remember all the hype Mercedes generated when they announced they managed to fit a big V8 inside the compact chassis of the previous generation SLK55 AMG? It was all about power, power and more power at the time, but things have changed a bit. A few days ago, we brought you the rumor that the company will be fitting a naturally-aspirated version of the new twin-turbo monster into the new two-seater. Now, the German company has brought forth official info, and things are all about power, economy and power.

THE SLK AMG that will make its debut at this year’s Frankfurt Motor Show this fall will indeed get the naturally aspirated V8 called M152, which is based on the the AMG M157 5.5-liter V8 biturbo unit found in E 63 AMG, CLS 63 AMG, S 63 AMG and CL 63 AMG. The new unit gets 62 horsepower more than the previous generation for a grand total of 422 hp, while peak torque is up from 510 to 540Nm of torque (376 lb-ft to 398 lb-ft). Due to strict emissions regulations, the US-spec model gets 415 horsepower and 398 lb-ft of torque.

The engine makes use of a new air intake, cylinder heads, valve drive, oil system, crankcase and, most importantly, a Formula One-derived cylinder deactivation system that cuts half the cylinders when they aren’t needed. Mercedes also fitted a new variable exhaust system that opens up after 2,000 rpm.

The Cylinder Management System can shut off four-cylinders from 800 to 3,600 rpm to improve fuel efficiency by as much as 30 percent over the previous generation. Mercedes says that the switch from four to eight cylinders is “immediate and imperceptible”, taking a mere 30 milliseconds, but automakers have a tendency to exaggerate these things: there’s no turbo lag, adaptive dampers are instantaneous and the tooth fairy exists.