Feel the power

Mercedes-Benz SL 63 AMG .

Ian Porter
October 23, 2008 - 4:04PM

YOU might be stepping into a Mercedes-Benz but when that car wears AMG badges you know you are in for a different experience.

It was clear that Mercedes-Benz wanted to sharpen up its image when it took over the AMG tuning house nine years ago. It was getting plenty of power and handling from the AMGs but apparently it wasn't getting enough attitude.

Until then, AMGs had been subtle on the outside and wild on the inside, so their drivers would not attract any undue attention from other road users or the constabulary.

More recent AMGs have taken on a "bad boy" appearance that sits comfortably with their wicked drivetrains.

The latest AMGs to explore this theme are the SL 63 and SL 65, two heavily worked-over variations of the company's premium SL two-seater range, which starts with a 232kW 3.6litre V6 and works its way up to a 380kW 5.5 litre V12.

AMG ignores those engines and plonks its own in-house motors into the SL. A normally aspirated 6.2 litre V8 with 386kW goes into the SL 63 and a twin-turbo 6.0 litre V12 with 450kW powers the even more outrageous SL 65.

We are talking about the SL 63 here, which only gives an extra 6kW compared with the standard V12. But this car cannot be measured just in kilowatts. It's real yardstick is intent, and that is pretty obvious from the hard-edged AMG front bumper and air intake design, which errs on the utilitarian side.

The V12 in the SL 600 and the AMG V8 in the SL 63 might be similar in output, but the engines are like chalk and cheese.

The V12 power curve peaks at 5000 rpm and is all about silky smoothness. The V8 peaks at 6800 rpm and has an 11.3:1 compression ratio which means it can crack like a whip. That's essentially what it does every time you turn the key. You don't need any throttle, the engine management system just blips the motor to around 3500 or 4000 rpm.
It gives you a start the first few times. Later, when you are used to it, it still gives you a tingle right down your back.

Which brings us to the gearbox which, despite the brilliance of the AMG V8, is probably the highlight of the SL 63 and - for the moment at least - not available in any other car.

The AMG Speedshift MCT 7 speed transmission is the first twin-clutch unit to appear in a Benz. MCT stands for multi-clutch transmission and the only similarity this unit has to the 7G-Tronic torque converter unit found in other SLs is the number of gear ratios.

Using the usual wet clutch system to replace the torque converter (some manufacturers are now developing twin clutch units with a dry clutch), the MCT gives the more direct connection to the engine needed if you are going to change gears in milliseconds.

AMG has programmed four different driving modes into the transmission's computer and, unusually, it is possible to pick the differences between each setting.

The dial next to the floor-mounted gearstick starts at C for comfort and progresses through S for sport, S+ for Sport Plus to M for manual.

The C setting delivers relatively slow (200 milliseconds) and smooth gear changes and a soft engine response to accelerator movements, allowing the SL 63 to pootle around town without too much trouble.

With the S setting, the gear change points are higher in the rev range and the changes themselves are 20% faster. What's more, on the way down, a double-declutching function - a blip to match the engine revs to the lower gear - kicks in on the S setting.

The changes are 20% faster again in S+ mode and finally get down to 100 milliseconds when the driver selects M and uses the steering wheel paddles to change gears.

The computer control and rapid shifting combine to eliminate the worst aspects of automatic driving, whichever ratio the SL 63 is in. On the way down, the computer reads the various inputs - road speed, engine speed, accelerator pedal - to shift straight to the correct ratio. Add in the neat engine blip available in the top three driving modes and there is no head nodding as the power comes off, a new ratio is selected and the power comes in again. With the MCT, it's just press and go.

AMG has also added an interesting little program called Race Start but it's only for people who own shares in a neck brace company. An intricate set of button pushes and paddle twitches allows the driver to launch the car with a pre-set engine speed, ensuring maximum acceleration while the MCT slams through the gears.

All the go delivered by the engine and the MCT has to be tamed by the chassis, and AMG has done a thorough job here, too.

The standard Benz three-stage Active Body Control suspension uses metal springs and dampers backed up by high-pressure hydraulics to deliver a range of ride harshness ranging from tolerable to race-car hard.

The hydraulics, tuned by AMG, deliver that uncanny experience of cornering hard with little or no bodyroll, robbing you of one of driving's traditional sensations. Your eyeballs are still squished to one side in their sockets but there is just no lean on the car.

The giant tyres put more than 25cm of rubber on the road at the front and 28.5cm at the rear, delivering prodigious grip.

Brakes are similarly powerful, with internally ventilated and cross-drilled discs all round clamped by six-piston calipers at the front and four-piston units at the rear.

The SL 63 interior comes fully equipped, as a supercar should. It gets the gun AMG sports seats with air cushions, ventilation and massage function, the Comand entertainment and navigation system and leather on the seats and steering wheel.

The folding roof gives the driver the choice of coupe or convertible and is sumptuously lined in suede-like material.

But, as is often the case, the folding roof basically eats the boot for breakfast, leaving room for a briefcase - maybe. It's clear that, while SL 63 owners may drive a lot, they don't play golf.

And driving is what this machine is about.

The SL 63 is an impressively fast car in a straight line - 0-100km/h in less than five seconds, top speed limited to 250km/h - but it really shines in the corners.

You constantly revise your braking points as you get used to how quickly the SL63 slows down and how much speed you can carry through a corner.

Once around the bend, the SL 63 rushes headlong towards the next, its acceleration belying the fact that it weighs more than two tonnes with a driver on board.

The hydraulics keep it all under control, but the speed with which things happen and the razor-sharp reflexes of the car keep the driver on full alert.

At the lowest setting, the suspension is very firm and the SL 63 can become lively on bumpier roads, manically scrambling across the surface as it heads for the horizon. The quick ratio, slack-free steering plays a big role here.

The hydraulic suspension keeps everything on an even keel, and also minimises fore-aft pitch, but lack of body roll makes it difficult for the driver to gauge how close the limit may be.

Of course, there are more electronics on hand to save the day should the SL 63's breathtaking competence lure the driver in too deep. The electronic stability control program - invented by Mercedes-Benz years ago - has three settings including ESP ON and ESP Sport, the latter with later intervention points. The third setting is ESP OFF and doesn't bear thinking about.

The SL 63 is something of a conundrum. It is a little too rough-edged to be a grand tourer with its noise and firm ride, and too large and heavy to be a track-day weapon (would you race your $400,000 supercar?). Yet its high level of engine and chassis performance mark it out as a serious driver's car worthy of consideration by anyone looking for something different in this price bracket.

AT A GLANCE
The car: Mercedes-Benz SL 63 AMG
The price: $401,235
Vital statistics: 6.2-litre V8;
386kW/630Nm; 13.9 L/100km;
330 g CO2/km; seven-speed Speedshift MCT auto