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Explained: The technology of the new Porsche 911 RSR (2017)

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The technology of the new Porsche 911 RSR (2017)
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' There's not much missing from the 1996 GT1 car. 'Joest team boss Ralf Jüttner takes a strong drag on his cigarette, takes a quick look at the rear of the new Porsche 911 RSR for the GT-LM class, grins and adds a very precise addition: 'Except for the turbo engine, of course.'

The new Porsche 911 RSR should be a winner again

Jüttner knows exactly what he's talking about: The Joest team won Le Mans in 1996 with the TWR-Porsche WSC-95, the Porsche works team took place z two and three on the debut of his brand new 911 GT1 car for the GT World Championship. The GT1 of that time looked like a knocked-out 911, in truth it consisted of elements of the legendary Group C Porsche 962 behind the original 911 front section - including a mid-engine installation position of biturbo technology.

The new one In terms of its spectacular appearance and mid-engine design, the Porsche 911 RSR for the GT Le Mans class is indeed a close intellectual cousin of the GT1 car from 1996. Porsche picked up the newcomer for the season finale of the Sports Car World Championship Bahrain, there the competition was allowed to take a look at the radical new development for the first time. Joest team boss Jüttner was among the eyewitnesses, who after a long period of observation said: “If he is as fast as he looks, then grace the opponents.”

Marco Ujhasi likes to hear something like that. The Bavarian is responsible for the works outings in GT racing at Porsche Motorsport, the new Porsche 911 RSR is his baby - and he doesn't feel like grace. After a sluggish last year of use of the current 911 RSR, the big turnaround has to be achieved in the next season - from chugging behind to winning types.

No turbo - 911 RSR stays with the 4.0-liter boxer naturally aspirated engine

Jüttner broached the greatest conflicting goals in two sentences: mid-engine and turbo technology. For 2017, Porsche implemented a mid-engine-like installation position, but dispensed with turbo technology, although all of the opponents' new GT-LM models rely precisely on the combination of these two core elements - see Ferrari and Ford.

'In terms of product policy, that was The starting position is completely clear, 'says Ujhasi,' the 911 is the icon and the backbone of Porsche, so another car was ruled out as the basis for GT racing. 'But the fact is that the rear-engine design is no longer that in the current battle situation Could be the ultimate in terms of tire usage.“Racing is about speed and especially about the consistency of lap times. This is a special requirement profile - and that's why we needed a special concept for the new RSR. ”

Ujhasi points out that the new engine mounting position is nothing more than a scaling for a special application. “On the road, we also have several versions of the 911, with rear-wheel drive and all-wheel drive or suction and turbo technology. In racing, we also need a special adaptation in order to meet the performance requirements. ”The technical regulations of the GT-LM class now offer this freedom: A manufacturer can freely choose the orientation and position of the drive - a special technical permit ( Waiver) is no longer necessary for such a show of strength.

Boxer engine in front of the rear axle

In principle, Porsche has reversed the arrangement familiar from the 911: the boxer engine is now in front of the rear axle, the gearbox moved aft, the wheelbase was stretched by 60 mm. But that is only an approximate description of the complexity, 'because the gearbox had to be positioned in such a way that the cardan shafts get where you need to go - that is, to the wheels,' as Ujhasi explains with a wink.

For the conversion, the racing department made use of existing mid-engine kits (Cayman and 918), 'as a result, the effort was pleasantly low,' explains Ujhasi. The advantages of the new installation position are obvious: firstly, the weight distribution is improved, which helps tire use, and secondly, the aerodynamics benefits because there was finally space to integrate a larger rear diffuser - Porsche has solved two problems in one go.

Above all, the force of the aero argument should not be underestimated: 'As the competition has developed, the issue of efficient downforce in GT racing is of decisive importance,' explains Ujhasi, 'and so far our hands were tied with the rear engine. ”Because the gearbox at the rear is of course much flatter than the engine, the rear diffuser could be wider and, above all, significantly higher.

Porsche
Porsche uses a naturally aspirated boxer engine in the RSR, the competition sets inTurbo engines.

The rear conjures up downforce at the front

Downforce through the undercurrent on the vehicle floor is more efficient than downforce by overflow. “In the best case scenario, you need both, the undercurrent is less stable than the overcurrent, especially in the dense traffic. And the GT-Ford has both - that's why it's so good, 'says Ujhasi.

Of course, the rear diffuser generates rear downforce, but its overall function is even more important:' The rear diffuser is the prerequisite for being able to use the Front axle downforce brings about, because at the front you are more limited due to the shape of the cars. In principle, the rear diffuser sucks in the air, which creates the necessary negative pressure at the front. ”In order to optimize the interaction between the diffuser and the rear wing, the bracket moved to the top of the rear wing blade in order to eliminate interfering contours and to allow a larger adjustment range.

The second aspect of the new engine mounting position is the weight distribution. Porsche does not provide any figures, but engineers of the competition estimate that Porsche may have shifted the percentage front axle load on the new 911 RSR to a range of over 45 percent - the cards for tire wear have now been completely reshuffled.

So far 35,000 test kilometers for the new 911 RSR

Marco Ujhasi admits: “We entered a new world with set-up and tire use. We can throw away all past experience and start again from scratch - but that's good news! ”Now you have to know that the tire contingent for GT cars in the Sports Car World Championship will be further reduced in 2017, which means that you almost always have to drive double stints in the races - and ideally with the most linear lap times possible.

'In the previous tests over 35,000 kilometers, we were pleasantly surprised at how close our simulations were to reality - that was very good straight away, ”explains Ujhasi. “The new weight distribution creates many new possibilities, and we are confident that we have drawn the right conclusions, also because the car reacts logically to set-up changes.” Smug commentary: “Yes, we can now understand why other manufacturers have not yet understood what was so difficult for us in the past. ”

The advantages of the motor installation position were thus successfully exploited, killing two birds with one stone. But the third fly in the Elfer-Gesurre was left alive - the naturally aspirated engine, although a trend change towards turbo technology is evident here. Why? Ujhasi cites three reasons: “A racing car is a total work of art, with every individual decision you have to prioritize the parameters with a view to the vehicle concept. And the turbo solution would have been a weight disadvantage, the big advantage of the new engine positioningwould have eaten again. ”

The calculation for the argument is complex: Depending on the base engine, a turbo upgrade costs between 15 and 40 kilos. “Our naturally aspirated engine is very light, which is why we would have had to invest more weight in order to implement a turbocharging concept here.” Marginal factors such as space and cooling requirements also play a role. Second, the sports department was committed to maintaining the product identity - after all, the top sports 911 (911 GT3) also has a high-revving naturally aspirated engine for the road.

Two concepts in one class

There is a certain risk behind the third argument: The intention of the GT rule makers is to balance turbos and aspirators fairly against each other - but that is exactly what went wrong in the Sports Car World Championship in 2016, to put it politely. Nonetheless, Ujhasi is confident for 2017: 'The regulators learned a lot in the first year with the new turbo engines, drew the right conclusions and implemented improvements for 2017, such as additional control of the charge air temperatures.'

In theory should The performance curve of a naturally aspirated engine with a reference displacement of 4.5 liters forms the basis for the turbo's speed-dependent boost pressure classification. The introduction of a torque meter required by Porsche to determine the real torque values ​​will not be implemented for the 2017 season - which must be seen as a disadvantage.

Porsche
The diffuser is wider and taller. The slim gear makes it possible.

Marco Ujhasi remains positive when it comes to the BOP and parity of vacuum cleaners and turbos: “There is a risk in principle, but you have I learned a lot about monitoring in the 2016 season with Ferrari and Ford. Defining reference curves is one thing, checking compliance is another. The theoretical idea is there, it has been recognized which gaps exist in monitoring under real conditions. If you close these gaps, we can have good competition in 2017. ”

4.0-liter boxer engine supplemented with direct injection

In the end, nobody can be interested in the Engine problem a two-class societyconjured up in GT racing: “We believe that it is possible to balance turbos and naturally aspirated engines. In theory, the engine would be partially neutralized by the regulations. And that's why we decided to take advantage of the overall vehicle advantages of the naturally aspirated engine, such as its lower weight, better balance and the benefit in terms of aerodynamics. ”

Direct injection added. It still gets its juice from a tank installed in the front of the car. In thoroughbred mid-engined cars, the tank is installed in the center of the vehicle, i.e. between the driver and the engine, which eliminates the negative effects of the fill level. A disadvantage for Porsche? 'This means there is a balance shift between full and empty levels, which is still relatively massive,' admits Ujhasi. 'And it is even a tad bigger than it used to be, because the tank is even more on the front axle - but we have to live with that.' RSR, reduced exclusively to its engine installation position, is wrong: The new figurehead in GT racing has also been fundamentally optimized in many other aspects, such as safety. The driver's position moved 50 mm towards the center of the vehicle, which significantly increases the survival space in the event of a side impact. “We learned a lot here from Richard Lietz's accident on the Virginia Raceway in August 2014,” says Marco Ujhasi. Porsche then created a new specification sheet - and has now implemented it.

'The accident resulted in a lot of calculations, and we drew conclusions from this: The vehicle structure has to absorb a lot of energy before the final block formation occurs, which is why The consequence was that we increased the survival space for the driver. It is important that the energy input into the driver is low, and that is only possible with a lot of deformation. At the end of this deformation phase, absolute protection must be provided by the survival space. ”For this purpose, the seat has now been firmly screwed to the vehicle, and the driver can be individually adjusted using adjustable pedals and steering wheel adjustment.

“ The driver now always sits in the same position, which is also important because of the obligatory mountain hatch in the roof, ”says Ujhasi. With the new safety concept, Porsche also benefited from the optimal starting position of the road 911: 'The good structures of the production car naturally helped us, the sill, for example, is already very solid and safe as standard,' emphasizes Ujhasi.

' Theoretically, we even meet the FIA ​​requirements without a cage, the safety cell is just an additional device, there are now a lot of reserves in it. The steel bars in the A-pillar, for example, are so strong that we would pass the pressure test on the upper cage point on the roof even without a cage! '

ThatThe six-speed racing transmission was redesigned for the RSR: “This is a completely new development. The primary goal here was not performance, but durability. You don't win races because of the gearbox - but you can very well lose races because of it! 'Porsche no longer uses pneumatic or hydraulic solutions for the gearbox:' We are the only GT manufacturer to drive with a shift drum, so with an electromechanical system, which is ours Highlight in the gearbox layout. This reduces the shift times, and the gears are engaged much more gently than before, which also reduces the interference from the transmission. The development goal was to maintain the weight - that's why we use a magnesium housing - but to increase the running time and robustness. '

Weight savings through chassis changes

Porsche uses RSR for the chassis of the 911 now also a double wishbone system on the rear axle, so no longer a multi-link axle. “This enabled us to improve the adjustability and ease of service, which increases the track time in the training sessions,” explains Ujhasi. For this purpose, the welded steel wheel carriers were replaced with milled aluminum parts. “All in all, we got the most weight out of the chassis.”

So the new Porsche 911 RSR offers many big and small revolutions - similar to the 911 GT1 from 1996. Whether it's Porsche racing innovations will also offer road customers in the future in the form of a special model has not yet been decided - but, one hears, very likely. That would fit, because in 1996 there was also a 911 GT1 for the road.

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