ALL SHOW AND ALL GO
2015 Porsche 911 GT3 RS 991. The new 991 911 GT3 RS stole the Geneva Motor Show, and with good reason. ‘Mr GT3’, Andreas Preuninger, talks us around his latest mind blowing RennSport creation…
The new #911-GT3-RS
stole the Geneva Motor Show, and with good reason. ‘Mr GT3’, Andreas Preuninger, talks us around his latest mindblowing RennSport creation… Story: Simon Jackson Photography: Porsche.
If there’s one certainty in the constantly evolving automotive sphere it’s that any #Porsche
wearing an RS badge will cause a riot at its unveiling. At this year’s Geneva Motor Show that’s exactly what the #991
GT3 RS did. And as I stood amongst row upon row of excited journos gathered from around the world prior to the covers being whipped off Andreas Preuninger’s latest road-going track car, that stir was tangible. In fact, I think the guy stood in front of me might have been in need of urgent medical attention. The car did not disappoint.
By now you’ll have all seen the stats: a 4.0-litre version of Porsche’s latest #DFI
engine producing 500hp; 460Nm of torque (around 339lb ft); 0-62 in 3.3 seconds; a top speed of 192mph; a body constructed from aluminium, carbon fibre and magnesium weighing ten kilograms less than the GT3 (at 1420kg); a staggeringly quick (borderline insane) Nordschleife lap time of 7mins, 20secs (faster than a Carrera GT); and a devastatingly aggressive aero-led aesthetic that will turn your mother-in-law to stone at ten paces. It’s all yours for £131,296, if there are any of the first UK allocation still available that is…
But as with any RennSport model to emerge through the doors at Weissach, the facts and figures don’t tell the 991 GT3 RS’s full story. Someone who does summerise the passion and importance of this car, though, is its creator – Andreas Preuninger. Fortunately he was on hand in Switzerland to talk us around it…
PREUNINGER ON ENGINES:
Despite the speculation that the new GT3 RS might be a turbocharged affair, the car is actually powered by an all-new NA engine based upon the DFI found in the GT3, just as we had predicted in the run-up to its full reveal. As you might expect this retuned direct fuel injection 4.0-litre mill boasts the biggest displacement found in any naturally-aspirated 991.
Preuninger is passionate about the powerplant: “We knew the GT3 engine could be hopped-up by displacement from 3.8-litres to 4.0 and we had already introduced this capacity with the  RS 4.0 so we couldn’t really go back on that. This was not a limited model, this car is the successor to the 3.8 RS, but still we wanted a 4.0-litre engine or one as great as the 4.0-litre engine.”
But if you’re thinking that a simple rebore is the extent of the changes made here, think again, as Preuninger is only too happy to explain: “There are a lot of differences to the GT3, it’s not like the [old] Metzger engine. We have a different crankshaft made out of a material that is only used on the 919 LMP car called V361. It’s a highly, highly clean steel that is melted and solidified several times. It’s a very pure, durable and special metal, a Star Trek-era material that should belong on the Starship Enterprise. It’s a horrendously expensive part, I cannot believe how much it costs, but it works!”
Porsche is typically modest about power outputs. Preuninger is modest, too, when discussing the power of the GT3 RS: “We’ve got different con rods, pistons, camshafts, cam springs and oil system – we touched a lot of parts in the engine internals. We wanted extra power. We wanted the RS to give more track performance. On paper it’s 500hp but in real life it’s a good deal more than that. We have to homologate GT cars way before the start of production and we always find something else during the development process. I like to be humble about these things.”
When pushed a little Preuninger explains that the engine is producing around 5% more than the 500hp headline figure, making it somewhere closer to around 510hp. This increase should be comparable with the reality of engine power outputs of the past versus the numbers stated by Porsche, given Porsche’s track record of underselling itself with things like this. The compression ratio of the 4.0-litre engine is identical to the GT3 at 12:9.1 but the increased stroke (taking the engine capacity from 3.8 to 4.0) means top-end revs are down by 200rpm over the GT3 to 8800rpm – final drive in a subtlety tweaked PDK gearbox increases from 3.97 (GT3) to 4.19 in this new RS car.
“It’s not that it cannot do the 9000rpms of the GT3,” Preuninger explains. “It just makes no sense. With a longer stroke the power curve drops off, then it feels like a diesel. It should explode up to the redline, then you have to shift. If you closed your eyes you’d have a hard time telling the difference between 8800 and 9000rpm. It’s still exciting at the top end.”
Using the larger 911 Turbo body in many ways created issues to work around for Preuninger and his team but it also had its benefits, too. Was there ever any chance this car might have been force-induced? “We just use the rear ducts [of the Turbo body] to cool the intercooler, and to fool everybody looking at spy shots into thinking it was going to have a turbo engine!” Preuninger chuckles. “We made use of the superwide Turbo body: it was a slick, cool solution for us otherwise we would’ve had to make new sides without intakes which would have been expensive [to homologate]. An effect of this is that the car has a specific sound; you hear the induction noise quite a lot more than on a GT3. I like that. It adds to the special nature of the driving sensation.”
PREUNINGER ON AERO:
One of the most striking features on the new GT3 RS is its aerodynamic package. Vents and wings seemingly protrude from every angle but perhaps the biggest talking point has been the beautiful slats on the front wings. “The slats in the front wings don’t just help downforce, they absolutely double downforce,” Preuninger claims with passion. “This is such a unique and important feature on the car. By opening up the front wheel fenders and allowing air to get vented we have massively contributed to the overall downforce of the car.”
Naturally, all of these new aero additions are functional rather than just cosmetic but it would be easier to dismiss their significance without understanding the reason for their existence. Preuninger is more than happy to explain:
“The problem with 911s is that if you want to create overall downforce you still have to carry balance. Making downforce at the back is easy, you just need a big wing in the air but you need a countermeasure at the front to have a stable car. If you have too much at the back the car pivots around the rear axle and you get loose steering.”
Preuninger’s logic is flawless but it isn’t until he draws a numeric comparison with the GT3 RS’ forebears that these latest additions are highlighted: “To give you a comparison, the 997 RS 4.0-litre was the number one for downforce. It recorded 107 kilos of downforce at 300kph. We used winglets and vanes to achieve that. This car [GT3 RS] has more than double that downforce: 350 kilos at 300kph. This is the same, if not a tad more, than the 918 Spyder! But, and this is a big point, the GT3 RS maintains the same drag coefficient as the GT3. The GT3 has 170 kilos, so less than a third. This is unheard of. You feel it, it kicks in early because downforce is a linear function – a curve.”
What that means is this dramatic increase in downforce is felt throughout the driving experience, even at speeds far lower than 300kph (186mph). As Preuninger points out, the linear nature of downforce means that even at half the speed the car will create half the downforce, so it’s a noticeable aid even when you’re not flat out on the race track. When combined with the mechanical grip the car is already creating, its wide 9.5-inch front wheels with huge contact patches, joined by Pilot Sport Cup 2s from the 918 Spyder (of which Preuninger is gushingly complimentary), is what combines to create this “quantum leap” in downforce between the GT3 and GT3 RS.
“Aero is a huge step over the GT3,” Preuninger says. “If I had to put a number on it I’d say 300% [better]. Then the tyres are the next factor. They’re 20% more sticky than on the GT3. I don’t want to bash the GT3, it’s a different animal but the GT3 RS was developed for the race track. The mission criteria for this car was different – it’s more track-focused, less day-today driveable – it’s built for a purpose, it’s a sporting tool. This is what the RS has always been about. We simply went a step further with that interpretation this time.”
The GT3 RS is arguably the most technically advanced 911 ever built, but could it be the last naturally aspirated 911 RennSport car? Preuninger seems open minded…
PREUNINGER ON CHASSIS:
“The suspension components are roughly the same as the GT3, they share nothing with the Turbos,” Preuninger explains. “We have a 50- millimetre wider rear track which calls for different parts, and it’s the same for the front axle. Everything is forged aluminium – all race bred. They’re a little bit more beefy than they would need to be solely for street use with upside down aluminium tubing dampers [Bilstein shocks] with increased spring rates [up ten percent over the GT3] and ball bearings are used all-round, like usual.”
This increased track means the GT3 RS has a greater stability and is generally more visually aggressive. But adding parts has not added to weight. In fact, Preuninger is obsessed with weight loss, as you might expect. “The front fenders we used are a lot wider [than the Turbo] to maximise the track from the front to the back,” he explains. “The fenders are carbon fibre rather than aluminium, which weighs just half that of the GT3’s fenders. We did a lot of bodywork on the car, too. The front lid is carbon fibre. It’s 1.5-kilos lighter. A real highlight of the car, though, is the roof. It’s made of magnesium sheet metal.”
The magnesium roof is a real masterstroke, and it’s an innovation that isn’t available on your average street machine. It’s not even something you’ll find on a high-end race car. Preuninger describes this all-new process with passion: “Three layers of sheet metal are welded together, shaped to form the curves of the 991’s roofline, then bonded in situ. The magnesium roof is one-kilo lighter than a carbon equivalent would be.”
Naturally this reduces overall weight but it also lowers the car’s centre of gravity. Innovative and highly advanced engineering – everything you’ve come to expect of the RennSport department. The process of lightening didn’t end there, either. “The rear end is made with a new pure material, too, which is 1.5 kilos lighter,” Preuninger says. “This was a new approach, we lost a lot of sound insulation material, too. There were a lot of places we could save weight on the car. The big 21-inch wheels with huge tyres weigh more, so we had to compensate.”
Increased wheel width and circumference and the 991’s sizeable body (in comparison with its forebears) are the reason this #Porsche-911-GT3-RS-991
has the smallest weight difference to its GT3 equivalent to date. Preuninger assures us that this doesn’t affect the driving experience and that the #Porsche-991
GT3 RS feels incredibly light and agile to drive. The 9.5x20-inch front wheels are shod with 265/30 tyres, the 12.5x21-inch rears are wrapped with 325/30 Michelins. The brake discs are 380mm with six-piston caliper items up front and four-pistons versions out back. PCCB carbon ceramics are available as an option.
“With this car we want to be in pole position. We want to be the best on the track – that’s what RS has always stood for,” he says. “That’s why it has PDK, that’s why it has the rear axle steering function – it’s well worth having these systems. There are endless discussions about PDK versus manual, there is no right or wrong, there are only differences. Differences in mission criteria. We put a manual in the Cayman GT4 to show we listened to the debate. For the future we don’t want to discuss this, we just want to offer both to our customers – if you don’t like PDK then fine.”
Of course, the PDK system fitted as mandatory in the GT3 RS has been tweaked but not as extensively as with other areas of the car. “We didn’t really touch the PDK system. The internals were beefed-up and the software is one generation ahead. That’s all we did to it.”
For circuit use there is a ‘paddle neutral’ facility and a ‘pit speed’ button which acts as a pit lane speed limiter such as that found on fullblown race cars. Rear axle steering features on GT3 RS alongside Porsche’s arsenal of modern electronic driving aids. It won’t surprise you to learn that PTV with rear limited-slip differential, PASM active dampers and PSM appear. The direct democratisation of parts from the #Porsche-918
down to #Porsche-911
is epitomised in the GT3 RS’s interior. The interior follow trends established in the GT3, but the carbon fibre bucket seats are based upon those found in the 918 Spyder. The Club Sport Package comes complete with the obligatory colour-coded bolt-in roll-cage, with the option of a six-point harness for the driver, battery master switch preparation and a fire extinguisher setup supplied separately. Sport Chrono is optional.
A 30cm strip runs the length of the front luggage compartment and roof, featuring a unique contoured surface reminiscent of classic air-cooled 911s.
At 1420kg the #991
GT3 RS is just 10kg lighter than the GT3 and 60kg heavier than the #997
RS 4.0 but the new car generates more downforce at around 100mph than the 997 did at top speed.
PREUNINGER ON THE FUTURE OF RS:
What might the future hold for Porsche’s RS models and how do they compete with rival offerings from the likes of AMG or Nismo? “I’m not a believer in this horsepower race, I don’t think that’s a clever thing to do. In my personal opinion 500hp makes sense at the moment. We’ve reached a certain point where 500 horses is enough,” Preuninger rationalises. “Because 700-800hp calls for bigger brakes, more sturdy suspension – it [the car] gets heavier and heavier. It’s not my overall engineering target to get 50hp more for each new generation of GT car. I’d rather turn it around and make the car lighter, working on the specific horsepower per kilo. I think that makes more sense.”
At the same time, he’s realistic about future power figures, which couldn’t arguably return to lower digits: “We wouldn’t turn back [on power outputs] but we have to concentrate on the overall package. This is not a dragster, it’s a track car – there’s a big difference. I hate to say it but this car is more comfortable than the GT3 on some roads because of the tyres; they’re big tyres with wide shoulders, so the residual comfort is high,”
And Preuninger is pragmatic about whether or not we will see an RS model with drastically more than 500hp in future: “When we introduced the #996
GT3 Mk1 in #1998
it barely had 350hp; if someone had told us that in ten years there would be a 4.0-litre version of this with 500hp we’d have said ‘yeah, come on’. The same thing goes for today, technology moves on. We have some clever ideas about what to do with this engine in the future so it has got a lot of potential.
“It’s the same as this Nordschleife ‘rat race’ – we are at 7 mins, 20 secs with this car [GT3 RS] – come on guys, everybody is talking about this with a pint of beer in his hand, mostly without being able to personally drive faster than 8 mins, 30 secs,” Preuninger says. “Anyone who has riden in a car with a professional driver doing 7 mins, 20 secs at the ’Ring knows what I’m talking about – this is really, really fast. For me it’s more important that everybody has fun with the car and can drive very fast to their own abilities. They can grow with it because more often than not the tool, the car, is more capable than they are. We are looking to make the car more confidence inspiring when we tune the systems. Maybe we could make a 7 min, 15 sec car but then it would be a dog to drive on the street – I don’t want that, everything is about compromise.”
Whichever Porsche this man touches next, you can be sure it’ll cause a riot. The new #991
GT3 RS hits UK roads in May priced at £131,296. It may be £30,000 more expensive than the 991 GT3 but judging by what Andreas Preuninger has to say, it’s worth every penny.
Car #2015 #Porsche-911-GT3-RS
ENGINE: 3996cc flat-six direct injection
TRANSMISSION: Seven-speed #PDK
BRAKES: 380mm ventilated discs with six-piston (front) and four-piston (rear) callipers, #PSM
CHASSIS: MacPherson struts (front), multi-link rear suspension. Electromechanical power steering, #PASM
Top Speed: 193mph (claimed)
0-62mph: 3.3 seconds (claimed)
Fuel Consumption: 22.2mpg (combined, claimed)
ON THE ROAD PRICE: £131,296
21-inch rear wheels are wrapped in the biggest tyres ever fitted to a 911. They forced modifications to the production line!