There's one rather crucial piece of information about the 997 Turbo that not a lot of people outside Porsche are aware of. It concerns the car's profit margins compared with those of the Boxster, and before I tell you what they are, it might be best if you find a comfy chair in which to sit. One that's good and sturdy beneath your backside and has no sharp objects within reach on which to damage yourself should you fall out.

Ready? To build and bring to market a 997 Turbo, it costs Porsche less than $10,000 more per car than it does to build and bring to market a Boxster. Work out the difference between the average price of a Boxster compared with that of the 911 Turbo and you get an idea as to how profitable Porsche's range-topper really is. And that's before customers go anywhere near the expensive options list.

So, it's not difficult to understand why the 911 Turbo is held in such esteem within the corridors of power at Porsche. If the Turbo sells, the company flies, basically. And if it doesn't, well… now that the concept of making money out of the banking world is no longer an option at Porsche, neither is the failure of the 911 Turbo. Hence the reason why they've thrown the kitchen sink at this latest and greatest revamped model.

Not that you'd know as much from a quick visual inspection of the new car as it appears in the metal. As ever with Porsches these days, the styling changes are subtle to the point of anonymity. But if you look closely enough there are differences (beyond the optional Turbo decals of the car in the photos), and once you spot them the previous model seems curiously passé.

This is precisely the effect Porsche's designers were seeking to achieve, of course. We live, after all, in an era in which you are no one unless you have the latest model, and it's an affliction that befalls the 911 Turbo owner just as badly as it does your average MP3 or smart-phone buyer.

At the front there are new LED lights in place of the old fog lights, while the indicators themselves are also new and feature suspiciously suave-looking LED bars. Tick the options list and these new headlights will help you see around corners better by “bending” as you turn the wheel, and at the sides there are more aerodynamically shaped door mirrors that provide an improved view of something 911 Turbo drivers rarely get to see: what's behind them.

The rump of a 911 Turbo has long been its most potent feature visually and, true to form, Porsche has preened the new car's tail to appear yet more aggressive. As at the front, there are new LED lights which, together with a bigger pair of exhaust pipes and an even wilder split rear wing, leave you in no doubt about the car's intentions.

Except that in reality, of course, you'd still struggle to grasp just how serious a car the new 911 Turbo is purely by looking at it. We'll come to the dynamic improvements in a moment, but for the time being consider this as a cocktail of improvements over a car that was already pretty close to the edge: eight percent better acceleration, 16 percent better fuel economy, 18 percent fewer emissions, 55 lbs less curb weight and less than two percent more expensive.

The key to most of the improvements is the new 3.8-liter, twin-turbocharged, direct injection flat-six engine. Previously, the Turbo had a 3.6 with a less fuel-efficient indirect injection system, but as a result of its new hardware – and a pair of new variable-vane turbos – the 3.8 now develops 493hp at 6000rpm and 479lb ft between 1950 and 5000rpm. Specify the Sport Chrono Package and torque rises to 516lb ft for 10-second bursts, but even then the combined-cycle fuel consumption remains at a deeply impressive 24.6 mpg.

Arguably of yet more significance is the new PDK gearbox, never fitted to the Turbo before because, until now, Porsche's engineers couldn't work out a way of making it reliable with over 450lb ft of torque. Now that they have, they've also taken the opportunity to rethink the ridiculous gear selection system that has come with PDK until now.

As an option you can at last specify fixed paddle shifters that sit either side of the wheel; the one on the right produces upshifts in the seven-speed 'box, the one on the left shifts down. The fact that the system is optional in conjunction with the Sport Chrono Package says as much about Porsche's stubbornness to admit its faults as anything the company has done in recent years.

As standard the PDK Turbo will be fitted with the silly buttons of the existing system, albeit mounted on a new design of steering wheel, but I doubt more than half a handful of owners will go without the paddles. Which, of course, will allow the cash register to chime once again at Porsche HQ.So how fast is the new 911 Turbo? On paper it'll get from 0-62mph in either 3.5sec with the regular six-speed manual gearbox fitted, or 3.4sec with the combination of PDK, Sport Chrono and launch control. Zero to 100mph takes an incredible 7.0sec dead with all of the aforementioned specified – little more than half a second slower than a McLaren F1 – and the top speed is restricted by gearing to 193mph.

On the road it feels outrageously rapid and yet almost entirely free from lag, lunging forwards even on a small throttle opening at low revs in a high gear. You need no more than 2000rpm showing before the motor is already at full stretch, and once it's there it just piles on the acceleration.

In fourth gear it has enough thrust to make you think long and hard before planting the throttle and holding it there for more than a few seconds. The outside world comes at you so fast that you wonder what people coming the other way are thinking. And in second gear it's just ridiculous; your passengers will probably scream.

It's the ease with which the Turbo now delivers its monumental performance that is so completely addictive – and impressive – especially with the new paddles fitted to the PDK gearbox.

There are varying degrees of gearchange speed selectable if you've specified the Sport Chrono Package (as surely most Turbo owners will), but in reality the system works brilliantly in all of its modes. And the paddles themselves are a joy to use compared with the wheel-mounted buttons.  

What of the handling? On the first-gen 997 Turbo there was perhaps a touch too much movement and not enough precision at higher cornering loads. The car would move around quite a lot if you drove it even at seven-tenths, and at full chat on a circuit it was far from Porsche's most incisive car.

Enter another new range of acronyms that have been introduced to the chassis, most of which are again optional (cha-ching!) and all of which dramatically improve the way the car behaves.

First up is Porsche Torque Vectoring (PTV) which, via a new mechanical diff, reduces understeer and increases the balance mid-corner by tickling the rear brakes if and when necessary. It sounds complex and is complex, but it also sharpens up front-end bite by a good 10 percent. PTV works in conjunction with PTM (Porsche Traction Management) and PSM (Porsche Stability Management) and can only be fitted if – you guessed it – you specify the Sport Chrono Package.

Also new are the 19in. wheels, which, mainly because they feature a new single centre-locking nut, are around 4 lbs lighter at each corner. That makes a small but key difference to the unsprung weight (read “ride and handling”). There's also a new engine mounting system on Sport Chrono cars that prevents the flat six from moving around as much at high cornering loads.

On the road you notice this new system in the way the tail end doesn't sway as much on turn-in. It used to be quite an issue with the previous-generation Turbo but, once again, Porsche has nudged the laws of physics in the opposite direction; unless you drive it very hard indeed you probably wouldn't be able to tell whether the new Turbo is rear or mid-engined.

And that's just how Porsche would want a driver to feel when they drive the new Turbo: blown away by its straight-line performance (check), impressed by its new-found ease of operation (check), staggered by its brakes, grip and handling (check), yet never feeling like they are venturing anywhere near the ragged edge (check).

As such, it's now an extraordinarily well resolved road car, the latest 911 Turbo. It even rides with remarkable refinement. It will continue, no doubt, to make Porsche its millions for quite some years to come. And being this good at what it does, it deserves to.

Steve Sutcliffe/Autocar