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A weightless sports car – just another victim of downsizing?

The Porsche 911 beneath the panels

07/06/2013 05:41 |  Comments: 

Contributing editor

Sipi is a fairy who hangs above us like a huge, ever-smiling, men’s fragrance-smelling umbrella. He can be called anytime, anywhere to lend a helping hand, and he’ll be there in an hour with one of his Transits for sure. A dangerously maniac car collector (the street in front of his house is full of his vehicles), a radio-control and model car freak, Sipos is a Swiss knife made of human flesh. Totalcar is just one job amongst his zillion occupations, but he endears it the most. Lives with a girlfriend and two dogs.

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  • Mitsubishi Sigma 3.0 24V (1992)
  • Mazda 323 TXL 4WD (1990)
  • 4 long-nose Transits (a 4x4 fire engine, a fire department staff car, an ex-Irish ambulance and an extremely oversized panel van, 1980-1984)
  • Dacia 1300 (1975, being restored)
  • Ford Capri 2.9i (1982)
  • Mercedes-Benz 280 SEL 4.5 (1972)
  • Ford Sierra Tournier 2.9i drift-car (1992)
  • Mazda 121 4dr (1993)
  • Suzuki VS1400 Intruder (1989)
  • Suzuki GSX 750 New Katana (1984)
  • Kawasaki Z1000 Police (1993)
  • Aprilia Habana (2000)
  • Volga M24 wagon (1984)
  • Ural M62 (1968, in pieces)
The 911 is a very special car, even those must admit the fact who are against it. Just once in a while a journalist gets the chance to look behind the scenes and get a hint how the magic is done.

I must admit, I am not a huge fan of the 911. I would rather choose any front- or mid-engined model than this rear-engined thing. Being prejudiced, the 911 will always remain a KdF Wagen (that's the prehistoric Beetle) on steroids for me. But I would never dare to question the engineering knowledge behind this model. Now I have an even bigger respect for all the fanatics polishing the rear-engine concept.

The latest developments of the 991 were presented to us in four topics, broken down to equal 30 minute segments, which was enough to run through the gist and get answers for a few short questions. They did not calculate with an ever asking Hungarian however. But you could see the twinkle in the eyes of the engineers – they loved talking about their job.

Intelligenter Leichtbau, Strukturklebstoff

First up was the presentation of the body and other lightweight structures. Saying that the engineers in Zuffenhausen have created a completely new car is not an exaggeration at all. The whole body is made out of a mixture of different materials: sheets of aluminium pressed in forms, cast aluminium alloys, steels of different strength are combined to create the shell of the traditional Porsche-shaped car. The sports coupe now has a 100 millimetre longer wheelbase, even the track is wider with about 50 millimetre.

As you can't just weld all these different materials together, all the parts are fastened with screws, rivets and structural adhesives (Strukturklebstoff) to create the body. As floor panels, doors and other parts are made of aluminium, the adhesive in the areas joining these with steel does not only fasten the parts but provides insulation and protection from galvanic corrosion as well. How effective are these glued bonds, you may ask? As the body's dynamic torsional stiffness is 20 percent higher than that of the previous model, so it should be pretty effective.

The roof panel is not part of the structure, so thanks to the new modular system it is only determined during final assembly whether a car will be fitted with a solid, a metal or a glass sliding roof. The rear spoiler does not rise out of the engine cover anymore. It has its own base made out of thin-wall cast aluminium alloy, providing a more stable base for the wing, creating even more downforce. As it is fastened to the rear of the body it also enhances structural strength. Using screws to fasten the base also makes the engine more easily accessible for maintenance. Well, it does not make access easier, it actually allows access, as the engine cover is not covering the engine itself anymore. Lift it and you will see only a few parts of the engine bay, but not the engine. Forget showing off the nice flat six to your friends in a parking lot.

Instead you can show off with the huge rear spoiler. It's not a simple, automatically raising and lowering component anymore. To improve efficiency it is over a meter wide, and an extra flap prevents air molecules merrily flying around to get under the wing. As the sliding roof moves outside of the body, it may change the way air goes around the top of the car. So the angle of the rear spoilers is changed according to the position of the Schiebedach. I have no idea how many Porsche owners want to drive on the Autobahn doing 250 kilometres an hour with the sliding roof open, but it is good to know that wanting to tan your bald head won't make your expensive Torschlusspanik-coupe take off. The mechanism moving this whole structure is just as complicated as a Swiss clockwork, just take a look:

Querbeschleunigungspotenzial, Gänsehaut Generator – nice, huh?

I can accept that it is no marketing bullshit when Porsche engineers tell me that 911s did not have an electric power steering because none of the existing solutions were good enough. Amongst other things, people buy Porsches because of the great suspension, so no one wants a lacklustre compromise in his/her super sportscar. This is why the Fahwerktechnik-abteilung have made the mechanism not turn the steering column but move the rack directly. It's a really sophisticated solution: a high-torque electric motor, assisted by a toothed belt and a ball nut, helps you to park the car, and in some cases tiny movements of the steering wheel also indicate which way you should steer to keep the car on the road. This way you can have the great steering response and feedback of a traditional rack-and-pinion and power assisted comfort.

The concept of Leichtbau, in English, light construction shows up in the suspension too: steel is only used where it's inevitable. All other components are made of aluminium, but not before the engineers worked out how to create rigid enough suspension arms out of a fairy's sigh. Truth be told, there is a lot to compensate with the use of light materials: the active shock absorbers and anti-roll bar links are almost certainly heavier than conventional ones. These components, parts of the PDCC (Porsche Dynamic Chassis Control) help to dramatically reduce body roll in corners and pitch while braking. The pictures taken on the test track show you what I am talking about. The drivers were really pushing those Porsches, but the lower edge of the bumpers is almost completely parallel to the track.

The Carrera S has 340 mm brake discs, six-piston callipers, the cooling has been improved and the callipers have been made stiffer in the front. Man, this diameter is even remarkable for a pizza, let alone a brake disc! The rear ones are not small either, with a diameter of 330 mm, and the rear callipers have 4 pistons each. As the Porsche has its engine in the back, there is a lot of weight on the rear wheels even when braking hard, so it makes perfect sense to use such huge brakes to convert kinetic energy into heat.

Two different gearboxes are available for the car, a seven-speed manual and a seven-speed double-clutch one (PDK – Porsche Doppelkupplung). The hottest feature of the manual is that it is the world's first seven speed manual gearbox built in series. As there are so many gears to shift, it was important to avoid mis-shifts. When using your Porsche properly, battling for fractions of a second on a racetrack, it takes just a little mistake to push the lever to seventh while shifting from fourth to fifth. It will not harm the mechanics, but it will ruin your lap time. To evade such a shame, there is a simple, yet effective mechanical limiter built in, letting you to shift to top gear only when in fifth or sixth gear. Anyway, there is absolutely no need for the seventh on the racetrack, it was meant to reduce rpm and fuel consumption on highway. The top speed is reached in sixth.

During the Porsche 911's evolution all the components got bigger except for the engine. The engineers must have washed the flat six in extremely hot water, as it got significantly smaller. Gosh, has the much hated trend of downsizing reached the sports car factory, too? Will we soon see Porsches driven by inline squirrel wheels? No, thank God, but the 3.6 litre engine will be replaced by a 3.4 one.

There's no need to worry about the output, it hasn't decreased. On the contrary! When you give free rein to 350 horses you won't have to worry about passing a flatbed truck. Should you feel this power is only good for driving to the mall and back, you can put the X next to the Carrera S when placing the order at your friendly Porsche dealer. 400 PS and 440 Nm of torque of the 3.8 litre flat six should be adequate in most cases. If a car is able to beat the Nürburgring lap record of the previous generation, it can't be that bad. Thanks to all the consequently made alterations the difference between the old and the new record is 14(!) seconds. A lap time of 7:40 seconds in the Green Hell is something to be proud of. This car deserves the name given by the Krauts: Gänsehaut-generator, in English, Goosebump-generator (Goosebumperator?)

Optimierter Rollwiederstand, Leichtbauprinzip – this is all about drag and weight

Efficiency is such an important issue nowadays that it is dealt with as a top factor even at Porsche. While reading about a hedonist sports car it is weird to face that it is this fuel efficient and that environmentally friendly. Sounds stupid when someone talks about the fuel efficiency of a car with 3,5 kg/PS weight to power ratio, but I must admit that the 8.7liter/100 km of the PDK fitted Carrera S is a remarkable value, even if it is sticking only to the official measurements which are way too optimistic to be believed, as we know.

The great thing is that all the improvements made on a sports car to make it lighter, faster and better ideally also make it more efficient and environmentally friendly. Fitting an electric power steering that does not have a hydraulic pump putting load on the engine not only makes the car faster, but it will result in lower consumption, too. This component alone could drop it by 0.1 litre. The engine stop-start system can save 0.6 litres of the expensive, at least 98 octane fuel. Using high-end brushless electric motors for the radiator fans could save one kilogram on these not so significant parts. All these little alterations add up to a 58 kg weight loss compared to its predecessor – even with the added extra weight of some newly developed parts.

With the sailing function of the PDK gearbox there will be no engine-braking when comfortably cruising and moving back your foot from the accelerator. This helps you not to lose your kinetic energy, just simply waft along, unless you press the accelerator again, hit the brake or shift down. Even the electrical system is designed to save fuel by putting load on the engine by the generator only when you are not using it to propel the car (that is when you are idling, engine breaking, sailing, etc.)

The most elegant innovation is the optimization of the cooling system of the engine and the gearbox. As the engine performs best (and has the best consumption and the lowest emission) at ideal temperatures, the engineers have created a totally new system. The coolant reaching the right temperature in the engine is first driven to the gearbox to transfer the heat to the gear oil to let it reach the operational temperature. The coolant is not allowed to pass to the front-mounted radiators until all lubricants have gotten warm enough. Once you see the whole system of tubes and hoses you can't help but ask how many litres of coolant there are all in all. According to the friendly engineer I asked, 20 litres – enough for at least three average cars.

Even the tyres with low rolling resistance, specially developed for the 911, add to the fuel efficiency. They can handle the recklessness of an enthusiastic Porsche owner and the top speed of 300 km/h, and still save petrol – a true wonder.

Ansauggeräusche, Abgasgeräusche – all about noise

With Teutonic thoroughness experts have summarized what messages the noises of the engine, the sounds coming from the exhaust system and the manifold send to the passengers of the car. Well, this really sounds like marketing bullshit, I probably had a smug smile on my face while the guy was explaining what sounds of higher and lower frequency tones mean to the users in relationship with sportiness, quality and other attributes.

Then the latest developments of their engineers were presented and, boy!, was I impressed: these guys work hard to make their car noisy! OK, these are not noisy the way streetracers' car are loud with bolt-on air filters and a rusty exhausts. The goal is similar, but hats off to the way they reach it. The mix of obsession, persistence and resources can result in unbelievable things. Only Germans and Japanese can go this far and run amok in such a sophisticated manner.

No one thinks that a Porsche exhaust system is a cheap structure welded of sheet metal and tube sections. The Carrera S's standard system that has little built-in flaps to tune the sound is no big surprise, either. Pressing the sound button is said to only change the sound of the car but has no effect on the engine power. You can tell that exhaust is a very important part of a Porsche by the fact that the development of the whole system is made solely in the R&D centre in Weissach (only the manufacturer of the components is a supplier – Eberspächer, known for its pre-heaters). Seeing the system completely made of stainless steel on a display made me wonder - has the glass fibre dampening wool of the mufflers been removed only to make it look better? Engineers then told me there has never been such a sound deadening material in the muffler, as these huge pots can fulfil all the requirements using stainless steel and nothing else. Well, the amount of Inox material used in the system would be enough for the production of all appliances in a bigger kitchen.

The real surprise was the witchcraft happening on the intake side of the engine. If you tell these maniacs – a.k.a. engineers – to make the car silent but let people hear the sound of the air sucked in by the engine, they will make it. You may think that it makes no sense to have a team working hard only to keep all the noises out of the cabin, and another one busy working to let you hear the way the engine is gobbling up huge amounts of air. But, on the other hand, it probably does make sense if they do it.

Anyway, the tricks they use to achieve this effect are mind blowing: as the air goes to the air filter in a closed pipe you don't hear a thing. To let you hear something they have cut a small window on the airbox, covered with a thin membrane, acting like a drum, and passing the sounds into the engine bay. Crazy? Yes, but it's just the beginning.

There is a branch leading off the intake tube which leads to another membrane following a cut-off valve. Opening this valve will let us hear as the engine, struggling for more air, sucks this membrane attached to the other side of a tube leading to the shelf under the rear window. So by pressing the “Sport” button you can hear all the noises the air intake of the engine makes, or just shut the valve of a device called Sound Symposer. Oh, by the way, there is another little flap in the intake system helping to get the perfect sound too. As the system produces less attractive noises above 5000 rpm, a tuneable Helmholtz-resonator will help to create the perfect sound experience.

I doubt that the sole purpose of the little throttle blip which happens at shifting down and also the shutting down of some cylinders to make shifting up quicker – is there to enhance the audio experience, as Porsche claims. Both features sound like really useful things to me, but altering the ignition timing while engine braking really seems just to be a gag - the bangs and cracks sound cool, but I am not sure whether the catalytic converter is as happy about this as the driver. When voicing my doubts the marketing guy and the engineer in charge looked at each other and said there's no need to worry, the cat can handle that. But I saw a little smile of conspiracy on their faces.

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