Mercedes-Benz SLK55 AMG revealed – NA V8 with 415 hp

Mercedes-Benz SLK55 AMG revealed – NA V8 with 415 hp

AUGUST 22, 2011 AT 11:23 AM BY DANNY TAN FILED UNDER CARS, INTERNATIONAL NEWS,MERCEDES BENZ

UPDATE: Hi res gallery of beauty and actions shots added

Mercedes-Benz has revealed its most powerful SLK to date, the latest SLK55 AMG, ahead of its Frankfurt world debut. As the range topping performance flagship of the third-generation SLK that was launched in June, the SLK55 AMG gets a new AMG 5.5-litre V8 engine with 415 hp and 540 Nm of torque, good for a 0-100 km/h dash in 4.6 seconds. Top speed is, as usual, restricted to 250 km/h.

No downsized twin-turbo V6 here, the SLK55 gets a naturally aspirated V8 with a “typical exhaust growl which only a large-displacement eight-cylinder engine can produce,” says Merc. This new M152 unit is based on the AMG M157 5.5-litre V8 biturbo engine that debut last year, and seeing service in the AMG versions of the E, CLS, S and CL.

Identical design features include the displacement, bore/stroke, distance between cylinders, ECO stop/start system and direct injection technology. Things unique to the M152 are the new intake air ducting, new cylinder heads, the modified valve drive, an adapted oil supply system and an optimised crankcase.

AMG boasts that no other petrol engine features direct injection at 2,900 psi pressure, spray-guided combustion and piezo injectors, all in conjunction with map-controlled cylinder shut-off, an all-aluminum crankcase with “spectacle” honing, four-valve technology with continuous camshaft adjustment, a high compression ratio of 12.6:1, stop/start and generator management – while revving to a maximum speed of over 7,000 rpm.

Did you notice ‘cylinder shut off’ from the list? That’s a new feature developed completely by Mercedes-AMG where cylinders two, three, five and eight are cut off under partial load, which lowers fuel consumption considerably.

Available over a wide range from 800 to 3,600 rpm if the driver has selected transmission mode C (for Controlled Efficiency), there’s still 230 Nm available in four-pot mode (enough for regular driving), and the reactivation process at 3,600 rpm takes no more than 30 milliseconds. By the way, this tech is also used in the 750 hp V8 engines in Formula 1.

Another new tech is the AMG sports exhaust system featuring a flap on each side. This resolves the trade off between an emotional exhaust note during spirited driving and a more discreet engine sound in the partial load range.

At engine speeds below 2,000 rpm the flaps remain closed. When the driver accelerates, the flaps open at an angle of 15, then 30 and up to 50 degrees. Under full load, the flaps are fully opened so one can hear the full AMG rumble.

Power is transferred to the rear wheels by the AMG Speedshift Plus 7G-Tronic auto ‘box with three transmission modes: Controlled Efficiency (C), Sport (S) and Manual (M). The automatic rev-matching function when downshifting shortens shift times, while a double turbine torsional damper with centrifugal pendulum adapts to engine speed and helps minimise vibrations in four-cylinder mode.

To improve handling, the SLK55 comes with AMG sports suspension with Torque Vectoring Brakes and AMG Direct-Steer system, the latter with a parameter function adapted to match the suspension.

There’s also an AMG-exclusive 3-stage ESP that gives individual control choices at the touch of a button: “ESP ON”, “SPORT Handling Mode” and “ESP OFF” for the very brave or very good.

After all the meat, here’s the garnish. The SLK55 is set apart by AMG light-alloy wheels, exclusive AMG body styling with AMG spoiler lip and two chrome-plated twin tailpipes at the rear.

Inside, the highlights are the AMG-specific analog clock featuring an IWC design, the AMG Performance steering wheel, with its flattened top and bottom sections (also has aluminum shift paddles), and the AMG instrument cluster plus main menu.