Edmunds: 2007 Mercedes-Benz CLK63 AMG Cabriolet

[Variance]

Vocal Hero

By Chris Walton

Date posted: 04-20-2006

There's nothing better than the sound of a big-bore V8 in the morning. That is unless you can lower the car's top at the touch of a button and enjoy it all the more, like we did in the 2007 Mercedes-Benz CLK63 AMG.

The new 6.2-liter engine, designed from scratch by the powerhouse AMG division of Mercedes-Benz, features a wildly "oversquare" design; that is, the diameter of the cylinder bores (102.2mm) is larger than the stroke (94.6mm) of the pistons.

In other words, you can almost distinguish each discrete explosion as the high-compression (11.3:1) engine bellows through the free-flow dual-tipped exhaust. For gearheads, it's one of those uniquely identifiable exhaust signatures that can only come from an engine of that design.

The new V8 is, or will be, at the heart of several 2007 AMG-equipped offerings, and in this application, it produces 475 horsepower at 6,800 rpm, and 465 pound-feet of torque at 5,000 rpm. That represents a 30-percent and 24-percent increase over the 2006 CLK55's 5.4-liter output.

Surrounding the magnificent new engine is an updated version of the CLK Cabriolet, suitably wearing new badges and bodywork, and new 18-inch wheels surrounding fade-resistant composite-construction front brakes discs. Once again, it appears that the U.S. market will not enjoy a coupe version of the CLK in AMG dress, although we drove one of those as well.

Big power, big smile

Our drive route comprised a healthy mix of freeway, sweeping rural highways and farm roads that showed off the engine's particularly wide-ranging abilities. Most of the time, the engine loafs around town, shifting at say, 2,000 rpm, using just about an inch or two of the throttle pedal. But that doesn't mean the car is slacking.

On the contrary, even at moderate engine speeds below 4,000 rpm, the 6.2-liter V8 is more than capable of propelling the 4,100-pound car with authority. Indeed, the torque plateau begins at just over 4,000 rpm and tops at 5,000.

Only when the road straightens out can a driver use all the throttle. When he does, the world goes all streaky and blurry 'round the edges as the tachometer slowly sweeps toward its rev limit just over 7,000 rpm. Speed seems to build exponentially because there are so few shifts occurring, and each gear feels like it lasts twice as long as one would expect from a seven-speed transmission.

Most of that's due to the rather tall (2.65:1) final-drive ratio in the rear end, but the effect is one of limitless acceleration. Mercedes claims a 4.7-second 0-62-mph (100 km/h) time (in 2nd gear), and the shift from 3rd to 4th doesn't occur until you've surpassed 100 mph. That's some tall gearing.

The car is electronically limited to a top speed of 155 mph, but doing the math reveals a real potential for just over 200 mph in 5th gear, assuming it could push that wall of air. The other byproduct is that fantastic soundtrack issuing from the tailpipes. When the conditions are right, you can actually hear spent gases rushing through the system like the great big air pump that it is.

It's not completely perfect

The AMG-tuned SpeedShift transmission is aptly named. Not only does it upshift quickly, it also does so smoothly by momentarily breathing the throttle between gears. But what it doesn't do is rev-match for downshifts, even when using the new-for-'07 metal paddles in manual mode. A skilled driver can manage to do just that, however, by blipping the throttle between gears, just after requesting a downshift, so why can't the software?

Then you reach a corner and it all goes to hell. Sure, the new brakes are tremendous, the suspension is sport-bred firm (but not punishing), and the Pirelli P Zero tires maintain heroic levels of grip, but the CLK's steering rack seems to have been overlooked in the AMG upgrade.

Having a bit of a dead spot on-center is fine to accommodate the "sneeze factor," but the slow-to-react ratio and numb, wooden feeling it offers is totally out of character with the rest of the otherwise sporty car. What one guesses as an appropriate amount of input for a given approaching corner is always an underestimate by about 30 degrees of steering wheel rotation, and there's very little information coming through the wheel up to the limit of tire grip.

The only time the rack and pinion steering feels the least bit communicative is just before understeer begins, as your arms are nearly crossed headed for the guardrail. On the other hand, with the ESP traction and stability control shut off, it is possible to "over drive" the CLK63 by using some lift-throttle oversteer midcorner to rotate the car and actually have some sideways fun. Even so, you've got to remember the countersteer is as slow as the initial turn-in was in the first place.

Clydesdales, baby

Our drive of this early-production European CLK63 AMG Cabriolet (and Coupe) came with no detailed information regarding U.S. pricing, options or expected fuel economy. Our educated guesses would indicate that when the car arrives here in July, it'll be priced at about $85,000, or just over the $79,000 BMW 650i convertible and the all-new 2007 Jaguar XK8 convertible priced at $81,000.

What you get with the CLK63 AMG for the $4,000-$6,000 over the competition is horsepower. The CLK outguns the BMW and Jaguar by 115 hp and 175 hp, respectively. That's what the AMG badge has always meant, and it appears the tradition still stands.

Link: http://www.edmunds.com/insideline/do/Drive...rticleId=110099

[pow]

Yay, the "6.3" is back, even though it's a 6.2.....