2012 Mercedes-Benz SLK55 AMG
All hail the tiny thunder.
Bless Mercedes-Benz. Bless that company a thousand times. The house that Gottlieb, Karl, and Wilhelm built might not be good at everything, but at the end of the day, it gets one important thing right: If you are going to build a high-performance car for public sale, then said car must sound bitchin’.Meet the 2012 SLK55 AMG. It sounds excessively bitchin’. Actually, that descriptor might be too modest—this machine is loud and raucous enough to wake the undersea dead. The naturally aspirated 415-hp, 5.5-liter V-8 under the SLK’s hood is the kind of powerplant that gives Detroit nightmares: torquey, smooth, and blessed with an exhaust note that makes the average V-8–powered American sled sound like a soprano eunuch. AMG calls this engine the M152, a fact worth mentioning only because it helps distinguish this V-8 from another Mercedes V-8. The M152 is a variant of the M157, the twin-turbo, 5.5-liter eight recently rolled out as a replacement for AMG’s aging naturally aspirated 6.2-liter M156 V-8.
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So Many Numbers, So Little Sense
Let’s get this down for posterity: The M156 used to live in AMG 63 cars such as the E63 and CL63. Most of those cars still wear “63” badging, a nod to the 1968–72 Mercedes 300SEL 6.3, despite the fact that they now are powered by the 5.5-liter M157. The M156 is still found in the C63 sedan, coupe, and new Black Series coupe; it also lives, albeit in slightly modified M159 form, in the SLS AMG. For the moment, the naturally aspirated 5.5-liter M152 is found only in the SLK55.
Confused yet? All you really need to know is that Mercedes-Benz badging can’t be trusted to accurately portray engine displacement—except in the case of the SLK55, one of the few cars whose number makes sense. Let’s move on.
Like all AMG engines, the SLK55’s powerplant specializes in torque. In addition to the aforementioned 415 hp, the 7200-rpm M152 cranks out a whopping 398 lb-ft of grunt, enough, we figure, to hurl the diminutive roadster to 60 mph in barely more than four seconds. The V-8 is oriented toward efficiency, at least as much as a 5.5-liter eight-pot can be; cylinder deactivation is standard, as are direct injection, variable valve timing, and a stop/start system. The cylinder-deactivation system, a first for AMG, can disable cylinders two, three, five, and eight by cutting spark and fuel and parking those cylinders’ valves. The transition is noticeable only in the form of a slight change in exhaust note—it shifts from a rumbling burble to a boomier, less-complex tune—and an indicator light on the dash. The cylinders go to sleep under light load and only from 800 to 3600 rpm. Mercedes says they need as little as 30 milliseconds to relight, and the active cylinders still produce up to 170 lb-ft of torque. The system only functions when the transmission is set to efficiency mode or when the folding hardtop is up, leaving the top-down experience unsullied by practical concerns.
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Mighty (Hefty) Mite
The SLK should weigh a whopping 3550 pounds—hundreds more than a Porsche Boxster or BMW Z4, both of which offer slightly nimbler handling and, in the case of the Boxster, gobs more steering feedback. This is as it should be. Mercedes isn’t known for building pared-down, die-hard sports cars, and the brand’s droptops have always seemed more suited to grand touring than corner carving. The 55 gets the usual pantheon of handling goodies—stiffer springs and dampers, a variable-assist hydraulic steering gear, 18-inch aluminum wheels, and a pseudo torque-vectoring function for the brakes that uses rear-caliper pressure to help the car turn in—and it’s happy sucking up winding pavement, but it’s happier still carrying big speed over long distances. The standard seven-speed automatic shifts smoothly and quickly, blipping the throttle on downshifts, but the engine is so flexible that you tend to forget the gearbox is there. Gripes are limited to a noticeable amount of nose weight—for better or worse, V-8–engined SLKs have always felt bigger than they are when pushed—and a rear-suspension tune that produces a lot of head toss and the occasional sideways hop over rough pavement.
The SLK55’s sports-car clothing and soundtrack can be misleading, but ultimately, this is a remarkably balanced, fast touring car. Pricing hasn’t been released, but figure on a sticker close to $69,000 when the model goes on sale in 2012. That’s anything but cheap, but the noise—that beautiful, lavish noise—is worth every penny.
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