Powerful, faithful and predictable. Michael Taylor tries out AMG's second attempt to improve its own engine.
2011 Mercedes-Benz CL63 AMG
It's raining in the Alpes-Maritime as AMG's new boss, Ola Källenius, slides into the passenger seat of his new CL 63 AMG. "This should be fun," says the guy in charge of the performance division of Mercedes-Benz. "Just fire it up and I'll show you what we made for you." What he has made for us is really what his predecessor, Volker Mornhingveg, made for us, because Källenius has only been at AMG for a handful of months - not long enough to produce an engine of this calibre, even if you are the man who headed the development of the current Mercedes-Benz Formula One engine.
It's not long enough to design a (mostly) new two-door body off the S-Class limo, either, much less fit it out with the standard AMG tweaks, like huge wheels and tyres, up-rated braking systems and hand-built interiors. That's probably why Källenius has taken to the CL with such fervour. It's fairly new to him, too, because he was taken through the programme after the opportunity to make changes had passed.
But, in terms of the CL 63's driveline, it's hard to see what he may have wanted to alter. This is the second stab AMG's had at its own engine and it's far better than the first. The 6.2-litre V8 (Benz always called it a 6.3-litre, but it wasn't) was a pretty good engine, for sure. It was smooth and it sounded superb. Yet, for those coming from the 5.4-litre super-charged V8 in the old E-, SL-, CL- and S-Class versions of the 55 AMGs, there just wasn't enough torque right down there, when you immediately step off the brake and on to the throttle. Sure, it picked up like a beauty over about 4,000rpm, but beneath 4,000 revs was exactly where the 55s did their best work.
So AMG learned its lessons and built this, a 5.5-litre V8 with two turbochargers, direct-fuel injection and 536hp of pure, unrelenting power. It's a seriously over-square engine, with the pistons only moving 90.5mm, so it promises whipping response and high-end power. But the two turbochargers mean it can offer the glory numbers up high and still pick up the gristle down low. How does 800Nm of torque sound? No? Well, AMG offers a performance package version of this engine and it's got 900Nm, another 26hp of power and has had the speed limiter adjusted so it does 300kph instead of the electronically limited 250.
That torque doesn't arrive up high, like it did in the last engine, either. The whole wall of 800Nm is there right from 2,000rpm and stays in a plateau until 4,500. It's attached to the latest version of AMG's wet-clutch seven-speed automatic, which changes gear with deceptive haste when it's in Sport mode and with deceptive smoothness for the rest of the time. It's essentially the same gearbox Mercedes-Benz uses for its bigger cars, but it's got AMG's own clutch kit on it to protect it from harm and to make the changes feel harder when you're pushing it.
It's also a thriftier beast at the pumps with a combined fuel economy number of 10.5 litres per 100km (impressive, for 2.12 tonnes), using start-stop technology to be 25 percent better than the old, non-turbo charged 6.2-litre V8. The biturbo manages this largely because of better fuel metering, and it's got spray-guided combustion and piezo fuel injectors, which can inject up to five times per stroke, creating a stratified layering of tiny droplets and air ready to be fried up on the power stroke.
It's a good home for a big engine, too. Benz launched its version of the CL at the same time and to hard-core it up a bit, AMG stuck to its own bonnet, lights, grille, tail lights and then threw in huge, 19-inch alloy wheels and Yokohama tyres. The dashboard will be familiar to anybody who's ever climbed inside an S-Class, with its row of odd, toggly buttons beneath the Multi Media Interface (MMI) screen, though Benz has followed Audi's lead and gone to Bang and Olufsen for the high-end sound system.
But no amount of leather or software tweaking in the MMI setup beats firing up the new engine.This thing rocks. Almost literally. It gives an involuntary shudder as the eight-pot fires up with a bwoar, then settles into a grumpy idling rhythm. The fat, leather-trimmed steering wheel, with its metal paddleshifters, beckons and the clutches engage to send the huge coupe out of the parking lot. In itself, this is a challenge. The CL 63 is not a small car. It's a slightly cut-down S-Class with a 2,955mm wheelbase. It's 5.106 metres long and 1,871mm wide. With a 2,135kg kerb weight, you wouldn't want the driver to misjudge and claim your foot, either.
And then there's the surprise. Once you've navigated the car park, the big coupe doesn't feel that big. It feels extremely comfortable, it rides well and it's civilised, with the V8 a deep, distant rumble. Find a little gap, though, and the CL 63 closes it in stupendous fashion. There's a deep induction howl, a growing, soft whistle from the turbos and then a throbbing, meaty exhaust song. So you set off in search of larger gaps. And larger. And larger.
You quickly figure out that there are few gaps out there large enough to let you use all the astonishing acceleration in all the gears. Conversely, it also means that you don't need a very big piece of clear road to dispatch any slower machines. That's because the SL 63 hurls itself, in a cloud of sound and fury, to 100kph in a supercar-esque 4.5 seconds. But even this isn't the whole story, because it rids itself of the next 100kph in what feels like about the same time. Realistically, it's probably about a seven-second exercise, but it's still brutally fast.
The gearbox is a fuss-free companion to all this violence, but that changes when you're in Sport mode. There, it decides that you wouldn't mind feeling a bit of the brutality that goes through a gearbox's internals, so it changes gear with a clanging, metallic thud and it does it quickly. The thing is, though, that for all its undoubted power, it's a faithful and predictable big thing. But it isn't quite fun.
The steering is solid and stable and it picks up Benz's new piece of wizardry to stop you drifting out of your lane by braking and steering you out of trouble. And that's about the only time it gives you any feedback. It gets heavier when you switch into the Sport mode, but it's still only weight, not precision. The multi-adjustable seats can reinforce you corner by corner, though some people find this a bit distracting (me) and turn it back to either bracing you tight for the twisty bits or a massage for the highways.
The brakes cope manfully with all of this tonnage being thrown around mountain passes. Unusually, they're a combination of a sliding-type caliper and a fixed caliper. It looks strange, but it works a treat. Then, when you're out of the mountains and driving sensibly again, the big AMG is a stupendous cruiser, flitting at 160 or so like a heavyweight champ arm-wrestling a four-year old. It's not going to be everything to all people, this car. But its character is now so broad, with its new engine and comfort, that it will be an awful lot to a soon-to-be happy few.