This could go one of several ways, writes John Simister. That's because this is not just a replacement for a popular model, it's a replacement for what seems almost irreplaceable.

After a few miles in the most radically recreated Porsche 911 since the water-cooled 996 of the mid-1990s, I am left simultaneously awestruck and bereft. There is absolutely no doubt at all that the new car, internally designated 991 in a curious demolition of numerical sequence, is faster, grippier, better balanced, better over bumps, roomier, more habitable and, surprisingly, lighter. But is it getting too close to perfection?

How the engineers hate that line of thought! Of course they want to improve their creations all the time, and are proud of what they achieve. It is not logical for 911-fanciers to crave that pulling and writhing of the steering wheel over topographical changes in the road surface, because it corrupts the purity of directional control. 'Besides,' says 911 project manager Michael Schätzle, 'original 911s didn't do it. It only started when the tyres got wider, and we wanted to get rid of it because some drivers were trying to correct the movements instead of letting the steering wheel move. And at 300km/h on the autobahn, this isn't a good idea.'

So while they were busy getting rid of the 911's foibles, why not put the engine in the front and be done with it? Because even Herr Schätzle accepts that would be a change too far. Porsche tried to do approximately that back in the 1970s, killing off the anachronistic 911 and replacing it with the 928, but the world didn't want to know and the 911 found itself reprieved under the patronage of a new company chief.

Michael Schätzle, I should tell you, owns a 1972 911T (in orange) so he knows about old 911s. It's currently having a rather faster engine built for it, the original 110bhp being insufficient. But even its racier flat-six will produce nothing like the 400bhp (up from 385) that now powers the 3.8-litre Carrera S that I have just driven, nor the 350bhp that now powers the regular Carrera. That's a 5bhp increase even though capacity drops from 3.6 litres to a Boxster- and Cayman-matching 3.4 litres, thanks to a shorter stroke.

Fuel efficiency improves too, with 911s equipped with the Porsche Doppelkupplungsgetriebe (double-clutch gearbox) achieving unfeasibly low CO2 outputs for cars of their pace: 194g/km for the Carrera, 205g/km for the S, equating to 34.4 and 32.4mpg on the fantasyland 'combined cycle'. That said, a Porsche 911 achieving over 30mpg is almost certainly a Porsche wasted on its driver.

This PDK transmission, as before, has seven forward gears. Much more surprising is that the manual now also has seven gears, the first of its kind and based on the PDK unit but with slightly shorter third and seventh gears. Other key points of the new car are a wheelbase longer by 100mm, a wider front track, a lower roofline and slightly shorter overhangs. The bodyshell contains much aluminium, notably for the bonnet, engine lid, doors, wings and roof. There's an optional active anti-roll system.

And now, two reasons to be worried. There's no conventional handbrake lever; in its place is an electric parking brake switch positioned under the dashboard near your outboard knee, Mercedes-Benz-fashion. How will that feel when you're edging your manual 991 up a hill in stop-start traffic – there's a standard stop-start system, by the way – or trying to park in a tight space on an incline? And the power steering is electric. How that feels is the biggest new-911 question of all.

I'll answer it in a minute. Before we climb in, though… does the new Porsche still look like a 911? It does, obviously. There are detail changes to go with the slightly altered proportions, such as an inverted front air intake and slimmer, rather Aston Martin-like rear lights under a raised tail ridge, and there's too much lettering on the tail now. But the shape still reprises the usual 911 silhouette even if, for only the second time in the breed's 48-year history, not a single panel is shared with the immediate predecessor.

Now we're inside, and the new 911 feels a bigger car than its modest numerical dimensional increases suggest it should. Partly it's because you feel more hemmed-in; the top of the dashboard stretches further away, you sit lower, the windscreen pillars are thicker and the centre console comes up much higher. This indulgence of design is one reason why the normal handbrake has gone, but there's no practical benefit (and certainly no sign of storage space) other than to bring the various Sport/Sport Plus/damper control/etc switches slightly nearer to your inboard hand.

However, the subjective interior quality is much improved, with sleeker-looking door trims and a tidier dashboard. The right-most dial of the usual five (with rev-counter still holding centre stage) now houses a display screen which shows trip computer information, Sport etc mode selection or need-to-know sat-nav instructions, these last duplicated from the adjacent central screen as needed.

I begin with a PDK car, vivid yellow and lacking the active anti-roll system. First impression? The ride, in normal mode, is significantly more compliant than before although there's still plenty of road roar on coarse surfaces. Second impression? The flat-six hum is deeper than before and the whine of the ancillary components, which used to deputise for the fan whine of old air-cooled 911s, has gone. Extraneous sensory bombardment banished, as promised with the steering.

Switch to one of the Sport modes, or press the button with a picture of paired tailpipes, and the sound deepens further as it did before. At times it gets a bit much; part of the effect is produced by the vibrating diaphragm of the 'sound symposer' on the intake tract, a gimmick a 911 shouldn't really need. The partial exhaust silencer bypass should be enough.

And the steering? Porsche claims it to be the most advanced and most natural-feeling electric system yet invented, with new levels of cleverness in the way it interprets the driver's torque inputs to create the correct effect from the cause. But it feels a bit sloppy around the centre, as if there's a loose rubber joint in the system, and there's little in the way of subtle picture-painting feedback, just a level of resistance the electronics judge suitable. The electronics are generally right, and big disturbances still come through to keep you connected with the terrain's larger variations. Most people would probably judge it fine, an efficient directional tool, but the conversation has been muted.

But, good grief, this is one fast car. The peak torque of 325lb ft (a small increase) now arrives at a higher engine speed (5600rpm against 4400), but with all those gears it barely matters. You can feel the urgency of thrust building until at that torque peak the 911 hurtles like little else, which makes the future Turbo, GT3 and others a very intriguing prospect. This Carrera S is claimed to reach 62mph in 4.1 seconds as a PDK with Sport Plus selected, and to continue to 188mph; the manual is in the same league. Maximum power comes at 7400rpm, at which point the 911 howls with almost piercing smoothness.

Now we cut to an airbase outside Santa Barbara, California, where a sinuous test course with slaloms, hairpins and fast, tightening bends is laid out. Here the longer wheelbase and wider front track should make the 911 calmer in its responses than the old car, but it's still rear-engined so it's bound to feel tail-heavy.

Which it does, but in the best possible way. The front wheels seem immune to understeer, biting with total determination as the Porsche flicks to a new direction. So you can nail the power sooner than ever, feeling the huge traction as you're catapulted out of the corner. I saw transient peaks of 1.29g cornering force in the slalom and 1.8g in the braking test, as recorded via the Sport Chrono pack. Nor is a tightening bend a problem; you simply hold it on the power and drift under perfect control in the direction you want, helped by the magic of the torque-vectoring system. Switch all stability aids off and the slides become snappier with quick corrections required, but it's all very benign by old-911 standards.

Out now on the road again, and into the mountains in a manual 911 with active anti-roll. This should be the proper car-nut's 911, but was the clutch this heavy before? Herr Schätzle says it was, but I'm not convinced. This and that confounded parking brake might be enough to force a PDK purchase if you drive in a lot of traffic, which is a watershed moment for one who would normally consider only a manual.

However, the seven-speed shift selects gears perfectly cleanly, and most of the time you just use it as a close-ratio six-speeder. Seventh is out to the far right and forward, upon which the lever leans at a drunken angle; an interlock prevents you from going straight there from fourth or vice-versa.

This 911 stays tangibly flatter in the corners, not that body roll is much of a problem even without active anti-roll. More important is that it steers more naturally, having lost the slight softness around the centre. Maybe that's the anti-roll system at work; whatever, the steering is probably good enough for a 21st-century 911, reflecting the purpose of the whole car. Given an engineer's imperative always to progress, it's hard to see how a new 911 could have been much different from this. Handbrake excepted, of course; what were they thinking?

So all would have been fine had I not sneaked drives in some past 911s which Porsche brought along for us to try. A 1985 prototype Club Sport battered the senses, felt fun and very dated. No sense in going back there. A low-mileage (just 3000km) 964 was a refined but tactile delight, a 911 representing an earlier optimum. A pre-facelift 997 rode worse than the 991 but felt smaller, handier and much more tactile in the steering, a BMW 3-series to the new car's 5-series.

There's nothing else new at the 911's price (in the UK £71,449, or £81,242 for the S) that quite matches it, but there's loss as well as gain. Officially, the new steering system gives an extra 0.37mpg and every little helps, but it may be an eco-concession too far. Objectively the new 911 is outstanding, but part of a 911's appeal has always been its streak of demanding imperfection. That's why I'd sooner snap up an almost-new 997 GTS while I still can. I never thought I'd consider a simple handbrake lever a bringer of joy, but I do now.

Text: John Simister
Photos: Porsche