2016 Porsche 911 Carrera S Cabriolet 991.2 vs 2016 911 Carrera 4S Cabriolet 991.2

2016 Porsche 911 Carrera S Cabriolet 991.2 vs 2016 911 Carrera 4S Cabriolet 991.2

A new direction? 991.2 C2S V C4S. For the last two generations, all-wheel drive has been faster than traditional rear-wheel drive. But has the C4S really turned a corner in offering a better sports car experience? Total 911 visits some curvy roads to find out… Written by Lee Sibley. Photography by Daniel Pullen.


RWD v AWD

All-wheel-drive 911s are now quicker than the traditional rear-driven layout, but are they really better?


Serendipity, they call this. It is the hottest day of the year in Britain, the 911’s on-board thermometer showing a scorching 34.5°C, and your favourite automotive magazine team are out on road test with a delectable double of 991.2 Carrera Cabriolets.

“The C2S can kick out, if you let it, forcing the 911 into oversteer”

Basking in the sun’s intense glare, both 911s are topless, their four-panel roofs stowed neatly under the curvatures of their respective posterior. I can’t help but feel lucky to call this ‘work’. As the favourable bright sunshine beats down on team Total 911, our 991.2 Carreras are delivering the full accoutrement of the traditional Cabriolet experience, namely a positively visceral auditory of the hard-working internal combustion engines behind us.

In 991.2 guise this means that, as an overtone to the snarling and popping of exhausts as each car rides in Sport mode, there’s a high-pitched whooshing from the turbochargers as we traverse a narrow corniche along the breathtaking Elan Valley’s southern front. Situated in the very centre of Wales, the road dissecting the Elan Valley has long been a Total 911 favourite for its brisk changes in elevation, pace and accompanying scenery. Save for the obligatory sheep inevitably loitering close by (perhaps tyre detritus and surplus tarmac chippings are the perfect garnish to the habitual Welsh terrain?), the road is relatively quiet, giving us plenty of space in which to exploit the boundaries of our cars.

This is just as well, as the fact both cars are Cabriolets is of little relevance to today’s journalistic test. The reason we’re here, then, is because the Carmine red 991 I find myself in has drive going to all four wheels, while the Graphite blue example my colleague is piloting employs the conventional 911 genetics of rear-wheel drive. In years gone by, a C2 v C4 head to head would be a largely superfluous exercise. The rear-driven car has always been a purist-pleaser, is faster, and doesn’t understeer so readily, while the C4 is intended for those whose 911 brief is unabated everyday usability. Now though, to use an apt metaphor, the terrain is different.

The 991 generation’s 100mm extended wheelbase and revised engine position, now sitting more atop that rear axle, has blessed the entire model line-up with a deftly balanced chassis. As a result, understeer has been greatly reduced, the C2 and C4 included. Then, when the Carrera went turbocharged for the 991’s second generation, something quite incredible happened: for the first time, the all-wheel-drive variant boasted a quicker 0-62mph sprint time over its rear-driven comrade. This means that in terms of its true, outright performance, the new C4S is now the de-facto choice for those wanting the fastest possible Carrera.

So where does this leave the rear-wheel-drive variant? Well, the difference in sprint time from 0-62mph between the C2 and C4 is just 0.1 seconds, hardly a night-and-day conclusion to proceedings. Besides, at Total 911 we don’t decide duels by statistics, we decide them by feel, deliverance and above all, emotion. The Carrera 2 may have its tail between its legs when it comes to a dash off the line, but overall the RWD and AWD cars are closer than ever before. So which edges it?

The Carmine red Carrera 4S was busy winning me over even before I took a seat in it. Entirely subjective I know, but the four-wheel-drive Carreras are visually superior to the Carrera 2s. Their wider body gives a more aggressive stance on the road (admittedly, I think this works better in Cabriolet form with the roof stowed) while there’s an undeniable beauty to that red connecting light between those rear clusters, something that the rather more simple Carrera 2 doesn’t have.

These extra aesthetic devices are a clue as to the additional engineering that’s gone into the all-wheel-drive 911. For while its rear axle is always driven (and biased), the C4 employs an active all-wheel-drive system using an electro-hydraulic multi-plate clutch with variable map control (PTM) to send power to the front wheels, too. Honed on the first-generation 991, the new Porsche Traction Management system is taken direct from the Turbo and is more sensitive than the previous model, responding quicker than it, too. Tied in with Porsche Stability Management and a host of sensors monitoring the rotational speed of each wheel, steering angle input and longitudinal and lateral acceleration, Porsche says its PTM takes no longer than 100 milliseconds to react at any one time. Blink and you will have missed it, quite literally.

To add to the traction armoury, 4S examples such as this get a limited-slip differential with Porsche Torque Vectoring, which brakes the inside rear wheel (on manual gearbox cars the diff is mechanically locking but for PDK it’s electronically controlled with PTV Plus, which is essentially more active). And that’s not all: C4s have a wider track than C2s by 2mm at the front and 40mm at the rear, though interestingly tyre specifications are for the first time the same.

Incredibly though, despite all of this technology, the car is never noticeably punting drive to the front wheels. To its immense credit, the Carrera 4S predominantly feels like a rear-driven car. Save for the torque distribution indicator on the instrument panel, which gives you live updates of how power is being distributed over each axle, a driver is largely unaware of where and even how that power from the turbocharged 9A2 engine is distributed.

Even at speed in a straight line, the C4S is supremely planted. There’s much less movement from the front of the car, the 4S rocketing along the Elan Valley’s more open stretches with an indomitable assuredness. When it comes to cornering, turn-in is razor sharp, the Carrera 4S leading from its nose through each turn as we cross the gorge and climb higher up the Valley’s northerly incline.

Much like the 991.1 before it, understeer on the four-wheel-drive car has been greatly reduced through even medium and fast-paced corners. Thanks to the work of PTV Plus and optional rear-axle steering, corners are disposed of in clinical fashion. The car’s insistence on maintaining its natural balance is striking: there’s no such weighting up of the front needed like on the 997-generation 911s and before, meaning you can brake later (even trail for much longer where necessary) and carry more speed into corners without even a hint of grip recession and understeer.

Try as I might – and even with PSM completely deactivated – the all-wheel-drive Carrera seems unshakeable, its grip levels apparently boundless. And that may well be where the 4S’s problem lies. It’s a fun car to drive, don’t get me wrong, but to me the 4S errs just a little too far on the side of ‘caution’ in a duel against flair. Simply put, I don’t feel like I’m getting anywhere near to the car’s or my own limit at any time, which curtails my enjoyment somewhat.

Eventually, we reach the historic remains of the Cwmystwyth lead mine where, after stopping for a look around its stone roadside carcass, Josh and I swap keys and I take my place at the helm of the Graphite blue Carrera 2S. Equipped with a seven-speed manual gearbox – and therefore a mechanically-locking rather than electrically-controlled LSD – the rear-driven car is technologically inferior to the 4S, with 100 per cent of available drive going to the rear wheels only and managed by Porsche Torque Vectoring. With no optional rear-steer here, the aft axle is passive, too, so it’s the most basic (read: purest) 911 C2S you can currently buy.

Though at face value the rear-drive car employs a similar driving experience to its opposite number in four-wheel-drive, it doesn’t take long for our twisting Welsh B-road to highlight some key differences. Pinning the accelerator to the floor, the chassis of the C2S moves around beneath the driver when at speed on longer stretches of uneven road, the load of the car more readily riding on the shoulders of those huge 305-section tyres thanks to the C2S’s narrower track width at the rear. Occasional, incremental inputs into the steering wheel keep the car finely poised as we bob and weave along the road while chasing the horizon, though nothing less than gracious levels of grip are ever in doubt here.

Approaching the tighter turns on the other side of the Elan Valley again, it is clear that a whole host of slow, medium and fast corners aren’t a problem for the C2S in terms of turn-in precision, it too benefitting here from the deft balance of the 991-platform’s chassis. Pinpointing the apex doesn’t exactly make for hard work here but while still plentiful, grip in the C2S isn’t as limitless as the C4S.

That narrower rear track width doesn’t let lateral load transfer so easily and, with a passive rear axle as here unable to push the car round a bend from behind, the rear of the C2S can kick out – if you let it – forcing the 911 into oversteer. Without that extra 50 kilograms of all-wheel-drive technology stuffed forwards in the C4S, the C2S is more vulnerable to that traditional 911 ‘pendulum swing’ behaviour too, as its weighty rear steps out through tighter hairpins, though its manner is nowhere near as stubborn as the rump of wayward 997s.

This doesn’t happen at will, though, and a concerted effort is needed to provoke the 991 C2S into oversteer. Even in rear-drive form, there’s an awful lot of rubber to unsettle: unlike previous generations, with the 991.2 both the Carrera 2 and 4 employ the same specification tyres, meaning the contact patch to the asphalt is exactly the same in both cars. While that means grip is seemingly infinite in the 4S, those slight revisions to the chassis layout of the 2S provide matching adjustments in the boundaries of available grip. The difference is therefore just that: slight, but enough to let the rear-drive Carrera retain its superiority in terms of flair.

It is for this reason that the rear-drive Carrera remains our favourite. Its dynamism is what defines it as a true 911, a sports car that has always delivered a dramatic driving experience. The latest 991.2 iteration is the most assured 911 generation to date in terms of handling superiority, yet crucially there’s still a smidgeon of vulnerability about the car in rear-drive form that means, on the road at least, it’s easier to break the hold of those rear tyres on the C2S. To provoke the same outcome in the all-wheel-drive car will involve a level of aggression that’s not at all palatable for a public road space.

In a nutshell then, the Carrera 2S is just much more fun to drive – and there’s even an additional 20 litres of space available in the front luggage compartment (145 litres versus 125 in the Carrera 4S), ever a worthwhile retort against the C4S’s remit of enhanced everyday practicality. Yes, in the order of balance we’d need to drive the same road with the same cars again in the wet to see if our outcome is any different, but in the blistering heat of the sun-drenched Elan Valley, it’s the rear-driven Carrera whose dynamic talents shine the brightest.

ABOVE Cutaway of the latest Carrera 4’s all-wheel-drive system shows how power – and weight – is distributed towards the front axle.

Model 2016 Porsche 911 Carrera S Cabriolet 991.2


Year 2016

Engine

Capacity 2,981cc

Compression ratio 10.0:1

Maximum power 420hp @ 6,500rpm

Maximum torque 500Nm @ 1,700-5,000rpm

Transmission Seven-speed manual; rear-wheel drive

Suspension

Front Independent; MacPherson strut; anti-roll bar; PASM; track width 1,541mm

Rear Independent; LSA multilink; anti-roll bar; PASM; track width 1,518mm

Wheels & tyres

Front 8.5x20-inch; 245/35/ZR20

Rear 11.5x20-inch; 305/30/ZR20

Dimensions

Length 4,499mm

Width 1,808mm

Weight 1,510kg

Performance

0-62mph 4.5 secs

Top speed 190mph

Model 2016 Porsche 911 Carrera 4S Cabriolet 991.2

Year 2016

Engine

Capacity 2,981cc

Compression ratio 10.0:1

Maximum power 420hp @ 6,500rpm

Maximum torque 500Nm @ 1,700-5,000rpm

Transmission Seven-speed PDK; four-wheel drive

Suspension

Front Independent; MacPherson strut; anti-roll bar; PASM; track width 1,543mm

Rear Independent; LSA multi-link; anti-roll bar; PASM; track width 1,558mm

Wheels & tyres

Front 8.5x20-inch; 245/35/ZR20

Rear 11.5x20-inch; 305/30/ZR20

Dimensions

Length 4,499mm

Width 1,852mm

Weight 1,580kg

Performance

0-62mph 4.2 secs

Top speed 187mph

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