Late last year we first heard that Mercedes-Benz, together with its high-performance AMG division, was going to replace its entire engine lineup with a new range of more fuel efficient direct-injected and turbocharged units. Today, we have the first solid details on one of the most exciting of the newcomers, a 5.5-liter V-8 that will replace the 6.2-liter unit found in the current AMG lineup.

Codenamed M157, the new 5.5-liter engine will feature direct-injection and twin-turbocharging technologies to ensure it produces more power and torque than the current 6.2-liter naturally aspirated mill.

It will be rated at 537 horsepower at 5,500 and 590 pound-feet of torque over a wide band of revs stretching from 2,000 rpm all the way up to 4,500 rpm. This is substantially better than the 525 horsepower at 6,800 rpm and 464 pound-feet at 5,200 rpm in the 6.2-liter V-8.

Other details include a final weight of around 450 pounds and a combined fuel economy of about 22.4 mpg when paired with AMG’s seven-speed dual clutch transmission. The current 6.2-liter V-8 rates in at about 16.3 mpg in most AMG models.

The first application of the new engine is due this summer in the 2010 Mercedes-Benz S 63 AMG, which will most likely be renamed the S 55 AMG. As for other engines in the pipeline, expect non-AMG models to get a less powerful 4.6-liter V-8 (naturally aspirated and turbocharged) as well as several V-6 units. Importantly, most will be designed to integrate with hybrid drive systems.

[Autocar]