Mercedes-Benz has released official pictures of the new SLK 55 AMG, which as well as being the most powerful SLK ever, makes use of cylinder deactivation technology to deliver over 30mpg.
The 416bhp V8 roadster has a combined-cycle fuel consumption of 33.6mpg, achievable mainly through cylinder deactivation which halves the number of combustion chambers in operation during periods of low power demand. The technology is borrowed from Formula 1 racing, where it's used under deceleration, around corners and in the pit lane. Other manufacturers, particularly General Motors, have been experimenting with V8s and cylinder deactivation since the 1970s, but never fully realised the potential. Mercedes has reduced the power exchange loss associated with cylinder deactivation by using an intelligent engine control unit and a special control valve.
The SLK’s cylinder shutdown is activated at the press of a button, but also works fully automatically. Even with only four pistons operating, 170lb ft of a total maximum of 398lb ft of torque is available, which Mercedes says should suffice for most driving situations. The re-ignition of the resting cylinders takes around 30 milliseconds, and should not be noticeable to the occupants. As far as looks are concerned, the AMG flagship model includes a special front apron with large air-intakes, tinted clear glass headlights and a grille in the front bumper. At the rear, a diffuser and chromed exhaust tailpipes help to distinguish the AMG from its lower-powered brethren. Options such as the neck-level Airscarf or a glass roof with photochromic function are available, as are numerous exterior and interior customisation options. Various options packages are also available, such as the AMG Package with firmer suspension, rear locking differential and compound brake discs.
According to Mercedes, competitors for the hot roadster are few and far between; the SLK is in a different league from the 306bhp Porsche Boxster S and 335bhp Audi TT RS in terms of power, while an M-powered version of the BMW Z4 is still pending. Prices for the SLK 55 AMG are yet to be confirmed, but it will go on sale early next year.
Text: Joe Breeze