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This is the most powerful SLK of all time, says Mercedes-Benz, and its V8 engine is the world’s most efficient. Isn’t that a bit like saying: This is the most delicious hot fudge sundae you’ll ever eat, and it’s got the fewest calories?
I won’t argue the first part. With 310kW and 540Nm available from its naturally-breathing 5.5-litres, the new SLK 55 AMG is, in fact, the most powerful and delicious version of the roadster in its 16-year history. And, while I wouldn’t describe its performance levels as outrageous as other current AMG derivatives, there is enough power here to give the traction-control warning light a cadenza at each take-off.
A big-honking naturally-aspirated V8 in a little body like this is a breath of fresh air from all the force-fed turbocharged technology that’s sweeping the performance car industry today. Not that I mind in the slightest that Merc’s (and rivals’) most powerful engines have turbos; it’s just that the initial pedal response from normal aspiration, and the way the exhaust flows through loud and clear, uninhibited by impeller blades, is a welcome change from what is fast becoming the norm.
Put foot to floor on pulloff and the 55 will squirm away from a robot, ESP light flickering all the way. With stability programmes switched completely off, it’ll break traction with a little help from a left-footed brake, but nowhere near as easily as, say, Merc’s own twin-turbo AMG 63 smoke machines. Simply put, there is no comparison here between this car and its current AMG brethren.
I do suspect, though, that had there been space in the new SLK’s engine bay for a turbo or two, Mercedes would’ve considered their inclusion. Forced induction is where it’s at today, and the flagship SLK might then have been named SLK 63, and would have performed even better than it does now - especially at Gauteng altitude. But, and this is a big but, Mercedes then might not have been able to lay its bold claim of having “The world’s most fuel-efficient V8 engine”.
Behind this giant quote is some impressive technology. The SLK 55 can, like some other V8-powered cars today (Chrysler’s Hemi for example), switch off four of its cylinders when not needed. It’s a seamless transition that, in all honesty, I wouldn’t believe was even happening had it not been for the little Eco4/Eco8 display message in the instrument cluster. This trick’s been learned from Formula One, where Nico Rosberg’s and Michael Schumacher’s race cars kill off certain cylinders to save fuel in slow corners or in the pit lane.
ALMOST DOUBLE WHAT MERCEDES CLAIMS
On top of cylinder deactivation, there are friction-reducing carbon-coated piston rings and silicone-lined cylinder bores, engine stop/start, and a long list of other efficiency-related things too technical to mention here. It all adds up to a claimed average fuel consumption of only 8.4 litres per 100km, that in actuality came to... drum roll please... 14.4 litres per 100km while on test with us. Okay, so it’s almost double what Mercedes claims, but not terrible by V8 sportscar standards.
Mercedes also claims 0-100km/h will happen in 4.6 seconds, but at our high-altitude test facility actually came in at 5.4. We’re still happy with that, especially after the realisation that extremely long-gear ratios in the seven-speed transmission also play a role in this SLK’s ambitious fuel drinkage claims.
It’s quite obvious that engineers wanted to keep revs to a minimum here and a set of very tall gears makes that happen. The transmission also defaults to “Comfort” mode on startup, every time, which means it upchanges early and often. This makes for a lazy feel while driving around town, and even when the slightly livelier “Sport” mode is selected the long, drawn-out gears make the SLK 55 feel somewhat sleepy.
Naturally though, this all means that high-speed cruising is this car’s forte, and in seventh gear at 140km/h the SLK flies along like a low-revving dart making a relaxed bee-line for the horizon. In fact, if it weren’t for the excellently insulated and well-designed retractable hard top, I’d happily call this a compact Grand Tourer. Perfect for long-distance highway-based road trips for two. The boot is slightly compromised space-wise, especially if you want to drive topless, but there’s still enough room for weekend luggage.
I think the new SLK combines nicely with this stand-alone naturally-aspirated V8 engine. It’s in no way as high on smelling salts as other AMG models, but still offers a spirited drive and a fantastic grumble worthy of Merc’s performance wing badging. You may need a strong whiff from the jar to accept the R975 000 (before options) pricetag though. Its closest German roadster rivals may not come with eight cylinders, but they’ll still give the SLK 55 AMG a run for its money in outright performance and they’ll make it look silly in value-for-money stakes. So, a delicious, low fat and very expensive hot fudge sundae it is. - Star Motoring
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