New Mercedes SLK 55 AMG boosts power and slashes emissions

Usually when we talk about those sledgehammer AMG cars it’s all about bhp, mph and g-forces. But this new SLK 55 AMG hits the showrooms in January with some distinctly bunny-friendly figures to grab the mpg and CO2 headlines. But don’t worry; you’re still looking at the most powerful SLK of all time.

Its newly developed AMG 5.5-litre V8 engine features a cylinder shut-off system amongst other eco-systems to trim the fuel fat, but still thumps out 422bhp and 540Nm of torque. Yet fuel consumption of 33.6mpg on the combined cycle and CO2 emissions at just 195g/km are 30 percent improved over its predecessor. A sub-200g AMG. Whatever next!

The SLK 55 AMG tops-off the SLK range, now in its third-generation; launched in March this year. This SLK stands above the others thanks to the usual and pleasant AMG tweaks to the alloys (bigger, lighter), the bodywork (lower, wider, spoilered), the sound-flap-controlled, twin-tailpipe-soundtrack (much, much fruitier), and the performance (62mph in 4.6secs, 155mph limited).

The new M152 engine under the SLK’s long bonnet is based on the AMG M157 5.5-litre V8 biturbo engine first seen in 2010, which powers the E 63 AMG, CLS 63 AMG, S 63 AMG and CL 63 AMG. Many design features are identical, such as the displacement, bore and stroke, cylinder spacing, the start/stop system and the direct petrol injection technology.

The differences lie – and you’ll need a re-engineering with turbocharging giving way to natural aspiration – in the M152’s new intake air ducting, new cylinder heads, the modified valve drive, an adapted oil supply system and optimised crankcase. All this good stuff also brings a heady 7,200rpm redline to top-off that grunt with a deep howl. 

But the biggest difference between this new N/A V8 tech and the turbocharged V8 on which it’s based is the new AMG Cylinder Management cylinder shut-off system - cylinders two, three, five and eight are cut off under partial load, which lowers fuel consumption. However, should the pedal hit the deep-pile footwell carpet hard all eight pistons will once again rock the power party. Formula 1 engines pull the same eco-trick. 

That pulsing power is chopped into less destructive chunks and sent to the rear wheels by an AMG SPEEDSHIFT PLUS 7G-TRONIC 7-speed automatic transmission which features three transmission modes: "Controlled Efficiency" – for eco-action, Sport – forget the bunnies, and Manual. The AMG suspension, as you’d expect, if firmer, flatter and faster.

The SLK 55 AMG interior takes its inspiration from the really big-dollar SLS AMG Roadster. We’ve got air vents that look like jet engines, plenty of brushed aluminium and the sort of sports seats, by AMG, that’ll weaken the knees of grown men and schoolboys alike, especially if one opts for the optional nappa leather and Exclusive nappa leather from the list that costs. 

Even without these expensive but desirable options, the new Mercedes SLK 55 AMG is expected to cost around £60k when it hits dealers in January of 2012. Full price and specification details to follow but surely any accountant worth his salt could wangle a write-off for such an eco-friendly autobahn-stormer. 























By Daniel Anslow

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