2013 Mercedes-Benz SLK 55 AMG road test
It wasn't long ago that having a V8 under your hood was a good thing. A symbol of power, speed, and luxury, it meant business whether your chosen ride was a half-ton truck, a sports car, or a stately luxury sedan. Today, noses are turned up at its presence, as if it's the sole reason why the ice caps are melting, and the hole in the ozone layer is getting bigger. In the age of hybrids and electric cars, the V8 is seen as excessive, thirsty, and unnecessary.
Of course, the V8 will live on for years to come, and there are plenty of new specimens on the scene. Look no further than Germany for some of the latest developments: BMW's new turbo V8 manages to extract 560 hp from 4.4 litres, and Benz manages similar output and astronomical levels of torque from its new 5.5-litre turbo V8. Both are thoroughly impressive.
So while we don't fear the immediate demise of the V8 on the whole, there is a subspecies in danger. It's the breed that doesn't have a set of turbos or a supercharger force-feeding air and fuel into its cylinders. It's the original, the naturally aspirated V8, and it's appearing to go the way of the dodo.
An engine to get excited about
As you can imagine, it was a pretty big deal when Mercedes-Benz announced it would be launching a new naturally aspirated V8 engine, so it's worth a deeper dive into the engine bay than usual. Called the M152, it's a derivative of the aforementioned twin-turbo V8 found in the E63, SL63 and others, sharing its 5.5-litre displacement. So far, the only car it's being used in is the SLK 55 AMG, and, incidentally, that makes it the only AMG to have a name that correlates to the engine's displacement.
Underneath the engine cover — complete with a plaque signed by its assembler — you'll find a sophisticated and technologically advanced powerplant. The old SLK 55 had three valves per cylinder and a single overhead camshaft. Not so with the new one; it moves to four valves per cylinder and dual cams, and adds direct fuel injection plus variable valve timing. The result is a massive spike in power to 415 hp and 398 lb.-ft. of torque, which is good for a 0-100 km/h time of 4.5 seconds.
A kinder, gentler, greener side
Of course, such an engine wouldn't be allowed to exist in this day and age without appeasing the world's environmental agencies. It's why the M152 packs the requisite efficiency oriented gadgets like oil and water pumps that only operate on demand, an alternator that regenerates power to recharge the battery, and of course, an idle-stop system that shuts the engine down at red lights. But the one feature that sets it apart from any other sports car is the Cylinder Management System, which uses clever hydraulics to transform it from a rip-roaring V8 to a four-cylinder half its size when you're cruising about.
Together, these technologies allow Mercedes-Benz to claim it as the world's greenest V8. In Europe, where carbon dioxide emissions are a big deal, the Benz squeaks by with a figure of 199 g/km — less than a BMW 135i. And while you probably don't care about CO2 emissions, its fuel consumption might raise an eyebrow or two. This V8 roadster has the same appetite for fuel as the C 350 4Matic Coupe. Who says V8s can't be efficient?