Mercedes-Benz SL65 AMG-from EVO ------------------------------

Belt up and brace yourself for the wildest SL, the 612bhp, 737lb ft, V12 bi-turbo SL65 AMG. Oh, and don't forget your aspirins


My head hurts. An hour after being handed the keys to the SL65 AMG there's the dull throb at the base of my cranium. As I'm not prone to headaches I can only assume that it has been caused by the mild impact of my brain againt the back of my skull every time this ludicrously potent SL's throttle has hit the stop. Then again, maybe it's been caused by excess boggling of the mind.

Described in just one word, the SL65 AMG is incredible; the price, the performance and the fact that it's a series production car, all beggar belief. The stupendously quick 493bhp SL55 AMG already exists, so you have to wonder who would want an even faster, more powerful model, especially one that looks all but identical yet costs £146K... a staggering £50K more.

Essentially that extra £50K buys you a very special engine - a hand-built 6-litre V12 with twin turbos that develops 612bhp. Yes, six hundred and twelve, a colossal figure that would stand out on the spec sheet of any supercar, and already does on that of its cousin, the Merc SLR McLaren, give or take 5bhp.

The mighty V12s that power the CL, S and now SL 65s are individually built on the top floor of AMG's engine facility alongside supercharged V8s for the SLR. An extensive development

programme has turned the already muscular 5.5-litre bi-turbo V12 that powers Merc's '600' models into this monster. Capacity is increased from 5513cc to 5980cc through a fractionally wider bore and much longer stroke, while all the bearings are stronger. The inlet cams have higher lift and longer duration, the injectors are recalibrated and controlled by a revised engine management system, and there's a higher-capacity oil pump and oil cooler. Externally the turbos are bigger and now blow at 1.5bar, while the air/water intercooler radiator is some 70 per cent bigger and significantly more efficient. One man is responsible for building each engine and his etched signature appears on a small plate attached to the aluminium and carbonfibre engine cover.
The result is that humungous 612bhp, delivered on a little plateau between 4800rpm and 5100rpm, and truly spectacular torque - no less than 737lb ft (1000Nm) between 2000rpm and 4000rpm. The SL55 and even the SLR don't get close, developing 516 and 575lb ft respectively. In fact, the torque of this extraordinary V12 is capped, presumably so as not to destroy the rest of the drivetrain - unrestricted it would churn out almost 900lb ft (1200Nm).

Even so, whichever way you cut it, fifty big ones to replace the SL55's supercharged V8 with an even more potent bi-turbo V12 takes some swallowing. There has to be more to it than simply having the daddy of all SLs. The owner of this 65, the very first to land in the UK, is a good person to quiz about the appeal of the über SL because his previous car was an SL55, and a modified 560bhp one at that. 'It's the delivery,' he says, 'somehow turbos are more exciting than superchargers.' Having experienced it myself, and nursing the headache to prove it, I can appreciate the distinction; when the SL65 kicks, the surge is more dramatic, more surreal than the essentially normally aspirated-style punch of the supercharged V8.

As you'd expect, the chassis has been further tuned by AMG to cope with the increased loads. The auto 'box clutch- packs are uprated, as are the drive- shafts and hubs, and the beefed-up differential casing contains a clutch-type limited slip. The roll-resisting ABC suspension is recalibrated, as is the almost indispensable ESP traction and stability control system. The brakes are significantly upgraded, too, with huge 390mm diameter steel discs up front clamped by massive aluminium eight-pot callipers. At the rear there are 348mm/four-pots that wouldn't look out of place on the front of many a serious sports car. As standard the SL65 comes with 19in rims shod with 245/40 rubber up front and 275/35 astern but our owner reckons they don't fill the arches convincingly and has replaced them with 20in Brabus alloys painted with 255/30 and 315/25 Continentals.
He's also had the side windows and rear screen tinted, adding to the air of restrained menace exuded by this glossy black SL. Inside it's business as usual, with knobs on; the facia is leather-trimmed and the neat suede finish for the sculpted dial shroud now extends into the nooks of the instrument pack's lower reaches. Twist the key and the starter motor whirrs with a high-pitched whine before the V12 catches and assumes a discreet, low murmur.

Blip the throttle and the note flares into something more expressive but nothing like the throaty roar of the SL55's V8. A trick is most definitely being missed here - 600bhp and £50K-worth of V12 should have a distinct, cultured voice, and if it can't come from the intake end because of the dampening effect of the turbos and their contorted plumbing, then it should come from the four tailpipes. First impressions, we're told, count for a lot, and if firing up the SL65 doesn't produce an irresistible urge to reach for your chequebook, it's got its work cut out.

Or so you'd think. As it turns out, the SL65 sells itself to you the first time you mash the throttle pedal into the carpet, an event that leaves a ball of emotions permanently knotted in your memory. This SL feels so smooth, so docile and effortless as you bimble through town that sudden arrival of the acceleration that lurks latent beneath your right foot is a severe test of the stoutest bladder. You stamp on the throttle, there's a momentary pause and then you're slammed forward so fast that you seem instantly to be 100 metres further up the road than you were. It's terrifying, exhilarating and amazing all at once, and if you keep the throttle pinned it carries on. And on. And on.

The speedo reads to 220mph and even though SL65s emerge from the factory with a 155mph limiter, it seems very likely that the speedo needle of a totally derestricted example would settle, finally, in genuine supercar territory, somewhere between 200mph and 220mph. Zero to 60mph takes just over 4sec, claims Mercedes, with 125mph coming up in just 12.9sec.
Partly it's context that makes the acceleration of the SL65 so stunning. It's a very comfortable car with a decent ride (despite the non-standard 20in rims and wider tyres inducing some fidget and low-speed agitation), the engine note is whisper-quiet on a light throttle, and there's clearly a lot of mass along for the ride. Yet even though the SL65 weighs getting on for 2000kg, the impact of over 700lb ft of torque doesn't half shift it. It's a sort of immovable object meets unstoppable force scenario, only with the scales tipped firmly in favour of the force.

There's another reason why the SL65's acceleration feels so phenomenal, why it feels as monumentally fast as most supercars I've driven, and why I emerged with a headache. It's because it's an auto. In a supercar with a manual you work through the gears, building to a crescendo, whereas the superb AMG Speedshift auto in the SL65 shuffles cogs swiftly and drops you right into the thick of the action every time you press the throttle. The fact that the rear tyres can translate so much energy into forward motion is impressive, even if the remarkably subtle ESP system does intervene noticeably in the first two gears (and occasionally in the next two).

Of course, in the interests of science, I did disable ESP to see what happens. In regular auto mode the back tyres spin up so fast that the engine quickly hits the limiter and the box shifts up, and then the same thing happens in second. And this is on warm, dry tarmac. Select manual mode, though, and you'll run against the limiter until you request an upshift, which makes things more predictable if you're deliberately playing with the rear grip.

However, what manual mode also allows you to do is feel the true depth of this engine's ability. Flick into fifth at as low a speed as you can - around 50mph and 1400rpm - then bury the throttle. There's a pause before the turbos catch on, then the most extraordinary sensation of a very big engine winding up. There's a deepening of the engine note like a big, labouring truck coming into earshot and simultaneously you're aware of a push in the back. Before 2000rpm is showing, the push has become an insistent shove and from thereon the acceleration gets ever crazier until it reaches stop-I-want-to-get-off fairground-ride proportions.
Mercedes-Benz SL65 AMG.

Engine: V12, 5980cc, 36v, bi-turbo


Max power: 612bhp @ 4800-5100rpm


Max torque: 737lb ft @ 2000-4000rpm


0-60mph: 4.2sec (claimed)


Top speed: 155mph (limited)


Price: £145,970


On sale: Now
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