Porsche 911 Turbo Cabriolet

It's mighty fast. And mighty expensive

Model: Porsche 911 Turbo Cabriolet;
Price: £96,130. On sale October;
Engine: 3,600cc, flat-six cylinder, 32 valves, twin turbochargers, 420bhp at 6,000rpm;
Transmission: Six-speed gearbox, four-wheel drive;
Performance: 189mph, 0-60 in 4.2sec, 21.9mpg official average, CO2 309g/km.

If you are very rich, maybe you just have to have everything. That could include a Porsche, but which one gives the ultimate rear-engined sports-car experience? You could have the priciest body style (the cabriolet) or the most potent engine (the Turbo, if we leave aside the rare-groove, hardcore GT2 and GT3 versions). It is an anguished choice. Such are the trials of wealth.

But you need worry no more. Porsche has now combined the last remaining uncombined 911 ingredients to create a 911 Turbo Cabriolet. Obvious, you may think, but is it, in fact, a clash of ultimates? A Turbo is all about huge speed and equally huge acceleration, and a Cabriolet is about experiencing the sun and the moving air and, for some, being seen in the process. Huge speed plus no roof could equal a fashionably hairless scalp.

Whatever, the bits existed so Porsche thought it might as well combine them to create the first convertible 911 Turbo since 1989. Today's is a fiercer beast, though, with 420bhp and the ability to reach 183mph with the roof open, 189mph with it closed, and to cannon from a standstill to 60mph in a scarcely believable 4.2 seconds.

This is the fastest roofless roadgoing Porsche there has been, albeit a short-lived accolade given the imminent arrival of the Porsche Carrera GT, a carbonfibre-bodied Enzo Ferrari rival with a mid-mounted V10 engine. The Turbo Cabriolet is mighty fast and mighty expensive at £96,130 (£7,890 more than a solid-roofed Turbo coupé).

It is not the most beautiful of Porsches, with too much droopy bodywork overhanging the wheels and too big a bottom, but the ample air scoops and exit ducts lend the body's lower half a strong aura of air-sucking aggression. The body is slightly stiffer than that of a regular 911 Cabriolet, thanks to extra reinforcment gussets welded and glued between the sill structure and the door pillars.

The speedy theme even extends to the powered roof, which can be raised or lowered while the Cabriolet is moving at up to 31mph, thanks to some very strong motors. (Most convertibles will not let you power the roof above 5mph or thereabouts.) A wind deflector to give those follicles high-speed respite comes as standard, incidentally, and you also get a detachable aluminium hardtop for winter driving.

One key advantage of an open 911 Turbo over a closed one is that you get to hear the heady harmonics of the twin-turbo flat-six engine all the more clearly. It is quieter than the engine of a non-turbo 911, but it breaks free into a full-voiced howl as you near the 6,800rpm rev limit to remind you of the 911 breed's four decades of aural exclusivity. And what the Turbo lacks in sound effects is balanced by bombastic, relentless acceleration, controlled by an accelerator whose response is as keen and consistent as a regular 911's ,once past a momentary softness, while the turbos spin up to speed.

Overtaking, at almost any engine speed in any of the six gears, is an ankle-flex away. But so keen is the engine to rev that you might as well change down; clutch and gearchange are smooth and easy, making the automatic/sequential Tiptronic option hard to justify, and suck yet more hairs from your scalp. Perhaps worryingly, you need little skill to exploit all this pace. Nor, unlike in the tail-spinning 911 Turbos of old, do you need the skills of a Schumacher to power this car through corners.

Four-wheel drive is the key, directing the engine's torrents of energy to where they are most needed, to the rear wheels most of the time, but diverting up to 40 per cent to the front wheels if the rear grip is about to be overwhelmed. You can feel this happening as you accelerate hard out of a tight corner, the tail pushing itself back into line and the front wheels hauling the 911 through, as if it is not a tail-heavy car at all. The Turbo's structure feels stiff and solid, too, despite the lack of a roof, and only the most awkward bumps invoke a shudder.

This, then, is the ultimate 911 for ultimate hurricane-in-the-hair thrills. It is not my favourite 911, though, because for me a proper 911 has to have a roof. Maybe I am just being a purist. Or maybe I have lost too much hair already.

THE RIVALS

Aston Martin DB7 Volante: £101,950.
Ageing but handsome design with Jaguar ancestry is revived with a 420bhp V12 engine, but a Jaguar XKR convertible has similar appeal for far less money.

Ferrari 360 Modena Spider: £112,195.
The mid-engined, aluminium-bodied Modena feels most like a race car to drive; sounds it too. Beautifully made but very expensive. Paddle-shift "F1" gearbox is a popular option.

Mercedes-Benz SL55 AMG: £91,345
Supercharged, front-mounted 500bhp V8 makes this a near-dragster, helped by ultra-responsive automatic gearbox, and folding metal roof is neat. Very desirable.