Mercedes readies 670bhp super-SL: Mercedes readies 670bhp super-SL

Right now, being a strategist in the product planning department at Mercedes-Benz must be a mind-stretching job. Late last year the company showed the eco-conscious F700 luxury saloon concept with its novel four-cylinder ‘DiesOtto’ engine, and this month we get details of a 670bhp twin-turbo V12 SL that will contort the mahogany jowls of its rich owners as it hits 60mph in less than 4sec before going on to within a spit of 200mph. To be launched at the LA Show this November, the super-SL is the latest Black Series model from Mercedes’ in-house tuner, AMG, and as well as having more power than any self-respecting supercar needs, it will come with a price tag of around a quarter of a million pounds.

The SL65 Black Series will, of course, be something quite special; less than 10 per cent of the standard SL65 remains and it features an extensive square-footage of carbonfibre. The whole front end, from the gaping mouth to the heavily vented bonnet and flared front wings, is crafted from the stuff. So too is the roof, which will be fixed (as on the SLK Black) and which has been given a more coupe-like, extended profile, and the bootlid, which features an active rear spoiler. Some 226kg has been lopped from the regular SL65’s kerb weight, giving the now 1850kg coupe a power-to-weight ratio of 368bhp/ton – the same as a Ferrari 599.

There are generous air intakes and vents in both the bonnet and front wings to help purge heat from the engine bay, which is crammed full of twin-turbo V12. At 670bhp, this is the most powerful road car engine Mercedes has ever produced, eclipsing the 641bhp supercharged V8 fitted to the SLR 722, yet it’s not much of a hike for the bi-turbo 6-litre, which develops 604bhp in the stock SL65 AMG. The extra power is liberated in part by 911 Turbo-style variable-vane turbochargers, and the V12 is coupled to the old five-speed auto rather than the new ‘Speedshift’ seven-speeder, launched recently in the SL63 (117). The newer ’box doesn’t have the torque capacity, even though the V12 is capped at 737lb ft (1000Nm) as it is in the regular SL65.

To help keep it carbonfibre-side- up, the wheeltracks are extended by 115mm front and rear, requiring generously flared wheelarches that should sit well with the recently revealed new wide-mouth SL face. Up front the SL65 Black wears 265/35 ZR19 tyres, at the rear 325/30 ZR20s, while the air suspension has been ditched in favour of a steel set-up with two-stage adjustable dampers, which saves a whole heap of weight. There’s a package of aerodynamic enhancements to aid stability too, including a venturi diffuser and that rear spoiler which sits flush with the trailing edge of the bootlid before rising into the air stream at a pre-determined speed.

Expect an interior that’s not as stripped-out as that of the CLK63 Black Series. The American market, the main target for this car, won’t accept carbon-backed race-style bucket seats and expects features such as sat nav. The uber SL will, however, have a CLK-style flat-bottom steering wheel and a tidily integrated roll-cage, adding structural rigidity.

The SL65 Black is not just an exercise in seeing how far the SL can be developed. The wider track suspensions will also be seen on the all-new AMG supercar, the Gullwing or SLC. This car, still in the early stages of development, has been spotted at the ’Ring disguised as a Dodge Viper, suggesting that it will be the successor to the SLR. Like that SLR, the Gullwing will be front-engined and it’s expected that it will use a new twin-turbo version of the AMG 6.2-litre V8 producing well over 600bhp. Meanwhile, the SL65 Black’s V12 will find another home in the new Pagani supercar, where it will develop up to 800bhp. What’s certain about the SL65 Black is that it will be physically challenging; repeated starts deploying the relentless, sledgehammer acceleration of the previous 600bhp SL65 were enough to induce a headache. You can’t help wondering, though, whether it’s Mercedes that might get the headache this time. Some 210 of the total run of 350 cars have been earmarked for the US, a market suffering its fair share of economic turmoil, and the fall-out seems to be affecting much of Europe, which is also becoming rapidly more CO2 sensitive. After a decade of wondering where the power-race between German car makers might end, the 670bhp SL65 Black could mark its zenith. What a spectacular way to finish, though.