For starters, the 2012 SLK has a new engine. Not a revised, warmed-over engine, but an all-new V-6 with a 60-degree angle between the cylinder banks. (The old 90-degree V-6 was derived from a V-8 design.) Not only does the new engine have an ideal angle for a V-6—a V-6 is more naturally balanced at 60 degrees—but it also leaves more room for turbochargers to sit alongside the block. Room for turbos underhood means room for a turbo version in the lineup. Whether or not that will happen remains to be seen. The inevitable AMG version would be the obvious choice for turbocharging, but when the SLK55 arrives, it will be powered by a naturally aspirated V-8.
For the time being, the top engine will be a 3.5-liter V-6. Equipped with direct fuel injection, the V-6 has a compression ratio of 12.3:1. The engine makes 302 hp at 6500 rpm and 273 lb-ft of torque at 3500. U.S. versions will get a seven-speed automatic. With the autobox, figure on a 0-to-60-mph run of about 5.5 seconds. The engine is smoother and less prone to droning vibrations than its predecessor, spinning happily and emitting a delightful intake snarl as the engine ferociously pulls past 5000 rpm on its way to the 6800-rpm shift point.
Upsetting the balanced controls and attitude of the SLK is the seven-speed transmission. Paddle shifters behind the wheel allow the driver to request upshifts and downshifts, but the car takes them as mere requests and doesn’t always comply right away. It’s frustrating to ask for a second downshift and not receive it until somewhere midcorner. The transmission also has a tendency to stumble from third into fourth at part throttle.