Take a moment to absorb the stats of the old engine: 367bhp at 5500rpm, 391lb ft at 4000rpm. Not exactly weedy though perhaps peak torque could do with arriving a bit sooner. No problem: the new engine lifts power by 36 per cent and torque by an astonishing 51 per cent, resulting in a whopping 493bhp at 5000rpm and a stupendous 590lb ft... delivered from just 1800rpm.

With masterful understatement, Mercedes says 'the performance figures are correspondingly impressive'. No kidding. Zero to 62mph tumbles from 6.1 to 4.8sec.
The obvious question is why has Mercedes deemed it necessary to give the CL600 such an enormous uplift in performance when most car makers would be happy to give a revised model a few per cent more. It's true that the arrival of the 470bhp SL55 AMG has made the top CL look a little limp, but it's probably been prompted more by the threat of the up-coming Bentley GT Coupe, with its estimated ΂£110,000 price tag and twin-turbo W12 delivering up to 740lb ft of torque.

The CL600 has required remarkably few modifications to accommodate its hugely more potent engine, essentially a slightly detuned version of that found in the Maybach limo. The five-speed automatic gearbox has chunkier gears to withstand the torque and there's a longer final drive ratio, but the chassis is untouched apart from bigger rims and tyres. The wheels are still flat-faced forged alloys but of 18in rather than 17in diameter, and in a more attractive six-hole design, while tyre size goes up from 225/55 all round to 245/45 up front and 265/40 astern.

You're more likely to identify the new 600 by its alloys than the other visual changes, which amount to clear lens bi-xenon headlamps and a tidier lower bumper design at the front and mildly modified rear light lenses. Inside there's a bigger sat nav/TV screen and new switches but that's about it. Fire it up, though, and the double-time starter motor whine and complex multi-cylinder growl that follows are pure supercar, albeit more distant sounding within the heavily insulated luxury cabin.
It's no mean feat getting twin turbos, twin water chargecoolers and their associated plumbing into an engine bay already packed with V12. The small turbos hang under each cylinder bank and feed pressurised air into charge coolers mounted on top of the cam covers at the rear of the V12 to take advantage of the space afforded by the rising bonnet line.

The turbos are quite small and thus spool up quickly to a maximum of 1.0bar boost, giving a torque curve that rises almost vertically between tickover and 1800rpm. It's then capped at 590lb ft to save the transmission and remains constant until 3500rpm before tailing off, relatively speaking, to around 540lb ft at 5000rpm, where maximum power is produced.

There's an increase in kerb weight of 120kg compared with the previous CL600, taking it to a hefty 2075kg, but power-to-weight sees a healthy increase from 191 to 241 bhp/ton.
The CL's sophisticated ABC (Active Body Control) suspension takes the extra mass in its stride, and first impressions are that the 600 feels surprisingly nimble and agile for such a giant. The steering is direct and nicely weighted, the ride is firm but compliant and almost the only evidence of the transmission shuffling through the ratios is the movement of the rev counter needle and, if you listen hard, the changing pitch of the V12's muted drone.

Bury the throttle and the note picks up some bass but you won't notice that because you'll be slammed hard into the backrest, jaw slack, watching the horizon accelerate towards you. There is a momentary lull before full torque checks in. No, correction. The CL takes off very sharply for a 2-ton coupe - and then gets even faster. It's not so much turbo lag as the torque converter firming-up in response to the torque of a 5.5-litre V12, just in time for the momentous thrust induced by the turbos. It's not as linear as the urge of the SL55's V8 and the sound isn't as downright menacing but that probably suits the CL600 buyer.

Dynamically it's never overawed by the performance. There's the occasional flickering of the ESP light indicating subtle traction control intervention (in the wet it's much busier, though still discreet) but ABC does a remarkable job of keeping the CL flat, poised and controlled and you're only truly aware of the forces being held in check by the chassis when braking hard for corners.

Pure, evo-style driver involvement isn't what the CL600 is all about, though. It's an extraordinarily sophisticated and refined inter-continental cruiser that just happens to have phenomenal performance a mere flex of the right foot away. Bentley's new four-wheel-drive Coupe will have its work cut out bettering this CL. And there is a more evo-orientated model due shortly, too: the new CL55 AMG, which has a 493bhp, 516lb ft version of the SL55's V8 under its bonnet. Seems Mercedes has gone power-crazy. Great, isn't it?