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First look: Mercedes reveals SLK flagship

White lightning: The flagship of the third-generation SLK roadster will reach 100km/h in 4.6 seconds.

Faster, more efficient SLK55 AMG launches next month ahead of first-quarter Oz debut

22 Aug 2011

MERCEDES-Benz this week revealed photos and performance figures for its forthcoming SLK flagship – the 55 AMG – ahead of its official debut at the Frankfurt motor show next month.

It will go on sale in Australia some time in the first quarter of 2012.

Although Mercedes-Benz Australia has yet to receive pricing indications, company spokesman Jerry Stamoulis told GoAuto it would be “not too far from the previous model”, which was priced at $179,360 when it was discontinued two months ago.

The new V8-engined roadster will accelerate from rest to 100km/h in just 4.6 seconds on the way to an electronically limited top speed of 250km/h.

As we reported last month, the top model in the third-generation SLK range is powered by a naturally aspirated version of Mercedes-AMG’s own 5.5-litre V8 engine, which appears in a range of larger AMG models in twin-turbocharged form.

Although only 22cc larger than the V8 fitted to the superseded SLK55 AMG, the new engine pumps out an extra 45kW of power and 30Nm of torque for a total of 310kW at 6800rpm and 540Nm at 4500Nm.

Mercedes-Benz claims the new M152 engine is the world’s most fuel-efficient V8 engine and “combines the lowest consumption figures with the superior power delivery and the typical sound experience which only a large-displacement eight-cylinder engine can provide”.

4 center imageIt lists combined fuel economy at 8.4 litres per 100km under the European NEDC regime, with CO2 emissions of 195 grams per kilometre.

This is a considerable improvement over the figures for the previous model of 12.0L/100km and 288g/km, confirming Mercedes’ earlier claims of a 30 per cent improvement in efficiency for the new model.

One of the key contributors to the SLK55 AMG’s groundbreaking efficiency is a cylinder shut-off system the company claims was developed through its Formula One racing involvement, where two or four of the eight cylinders are shut down when cornering at slow speeds, when trundling around behind a safety car or during pit stops to save fuel.

In the SLK55 AMG, four cylinders (numbers two, three, five and eight) are cut off under partial load – over a wide engine speed range of 800 to 3600rpm – to lower both consumption and emissions, so long as the driver has the transmission set in the ‘C’ mode for “controlled efficiency”.

But even when the car is running on only four cylinders, it produces some 230Nm of torque. If the driver demands more than that, the engine switches to eight cylinders immediately (30 milliseconds at 3600rpm) and imperceptibly, according the Mercedes-Benz.

Other fuel-saving devices include the standard idle-stop system, which switches the engine off when the car is stopped and restarts it when the brake is released, and a generator management system that disconnects the alternator to reduce engine load.

The 5461cc M152 engine features direct injection, four valves per cylinder, an aluminium block with five main bearings, a forged steel alloy crankshaft, carbon-coated valves, variable camshaft adjustment, aluminium pistons and friction-reducing cast-in Silitec cylinder liners.

Power is delivered to the rear wheels via the standard AMG seven-speed automatic transmission.

The SLK55 AMG sports revised styling to the regular SLK, which was launched earlier this year, including an SLS-style wide-mouthed grille, larger air inlets in the front apron, AMG-specific LED daytime-running lights, vent grilles with chrome fins, more sculpted side aprons, a black diffuser at the rear, and darkened headlights and tail-lights.

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