Electronics aside, the CLS63 AMG stops like a sports car, and goes with almost as much enthusiasm as a race car. Its 6.2-liter V8 is a welcome improvement. Previously powered by AMG's supercharged 5.5-liter V8, this car with was fast. With the new 6.2-liter V8, it's blindingly quick but it's also super smooth. With 507 horsepower, the naturally aspirated 6.2-liter V8 delivers slightly more power than the supercharged engine it replaces. The 6.2-liter engine gets racing-style features such as dry sump lubrication, which ensures proper oiling under extreme g-forces.
This is the first AMG engine matched with the Mercedes seven-speed automatic transmission. Called, the AMG Speedshift 7G-Tronic, it pairs with the 6.2-liter V8 to form one of the most impressive powertrain combinations from Mercedes in years. Throttle response is instantaneous, automatic downshifts nearly so. The manual control electronics, which allow a driver to shift the transmission like a manual using either the shift lever or paddles on the steering wheel, are excellent. Speedshift allows the driver to hold a gear right at the 6.2 V8's 7200-rpm redline, where it's much silkier than the previous supercharged engine. There's a nice burbly exhaust tone at part throttle, and something more like a rebel yell when you floor it.
In the CLS63, the air suspension is tuned with a bias toward the handling side of the equation, or more firmly than some owners might like. It's also fitted with larger, Z-rated tires. In our view, it's not uncomfortable, and the payoff in improved response is worth it. Most Mercedes-Benz cars will go along for the ride when pushed, behaving predictably. The CLS63 AMG likes to be pushed. Think of it as a more willing participant in a spirited drive. SCCA Trans-Am champion Tommy Kendall gave took us on a couple of laps around the fast 2.5-mile Willow Springs International Raceway and quickly showed that that CLS63 worked at the limit of its tires very well at high speeds. Kendall had little trouble changing direction with a quick lift of the throttle while sliding the CLS63 through the turns. Next Page