The Mercedes-Benz SLK55 AMG set to debut at the Frankfurt International Motor Show will feature a new 5.5-liter V8 engine. The recently spied SLK55 is sure to draw a crowd, looking sleek and powerful running around the track. The new hand-built motor is a naturally aspirated version of the new CLS63 AMG and E63 AMG's twin-turbo 5.5-liter V8. The new SLK55 engine has seen its power boosted by 60hp to a nice 416hp. Torque has also jumped up from 376lb-ft to 398lb-ft.

Stop-start has been added and Mercedes also found some ways to improve the fuel economy and cut the CO2 emissions. F1 technology served as inspiration for the AMG Cylinder Management shut-off system. The engine can run on just four cylinders under partial loads to boost the economy. The hefty 30 percent increase for both gives the new SLK55 a 33.2mpg combined economy with a 199g/km CO2 emissions. Mercedes has given the SLK55 a sports exhaust system complete with two independent rear silencer flaps. As the driver hits the gas, the exhaust note progressively gets louder.

Debuting alongside the SLK55 AMG will be the SLK250 CDI - the diesel version of the SLK55. It will feature Mercedes oft-used 201hp four-cylinder turbo-diesel engine. A Mercedes spokesperson expounded on the merits of the diesel: "There seems to be the necessary demand for diesel cabriolets. We've seen good sales of diesel E-class cabriolets and other manufacturers have had a lot of success with similar models, so it only makes good sense to add it to the SLK." The Mercedes-Benz SLK55 AMG is set to debut at the 2011 Frankfurt International Auto Show in September.

The SLK250 CDI will price at around £34,000 (est. $54,777) and the SLK55 AMG should price upwards of £55,000 (est. $88,610). Both models should be in dealerships by spring 2012. Photos courtesy Pro-street.dk