E&HTI gets a rare opportunity to visit Porsche’s state of the art wind tunnel in its Weissach Development Centre.
“I always say electromobility is a little bit the revenge of the aerodynamicist,” says Francesca Cogotti, Aerodynamics, R&D, Porsche. We’re chatting to Cogetti and other members of the Porsche team in Weissach, in Porsche’s inner sanctum, with a rare opportunity to witness the wind tunnel running. Commissioned in 2010 and pressed into service in early 2015 it’s been in operation almost constantly since, with the first shift turning up at 7am and leaving at 3pm, before the second shift takes over until 10pm.
“Nowadays aerodynamics is even more important,” explains Cogetti, “And we really need to spend a lot of time in our wind tunnel for certification. We test each car for homologation, covering every different wheel and tyre configuration; for ride heights, with things like the active grille shutters open or closed; or the position and type of the rear spoiler. We must measure all of that and more, to allow the cars to be certified.”
Somewhat unsurprisingly a significant amount of time is spent eking out efficiencies that allow electric cars to travel further between charges. But naturally, this being Porsche, there’s also a significant focus on performance. To demonstrate that today the tunnel team will be running three Taycans ‘in the wind’, with a Taycan Turbo S being followed by a Taycan Turbo GT before a Turbo GT with Weissach Package being demonstrated within the state-of-the-art facility, as well as outside on track.
Christopher Sachs, Complete Vehicle Line Development Model Line Taycan, highlights the significance of the wind tunnel, saying: “When the idea came to make a hot Taycan model, we knew if we want to perform on the track, then the aero was one of the first things we must work on, because with the regular car there’s little bit of lift on the front axle. We decided to add downforce, but in two steps, with the Turbo GT and the Turbo GT with the Weissach Package.”
Sachs continues: “With the new Taycan we’ve worked on improving the aerodynamic efficiency, but also improve the aerodynamic balance, with real gains thanks to work here in the wind tunnel.” The previous Taycan Turbo had a drag co-efficient of 0.22, with the Turbo S being 0.26 which, Sachs says, “were excellent values in 2019, and not just for an aerodynamic car with small tyres – but as a performance car with a sporty body.” Juggling the conflicting desire for increased range though greater aerodynamic efficiency while also gaining a more dynamic aero balance by reducing the front axle lift is tricky, but that’s what the team wanted. “It’s relatively easy to increase the downforce,” says Sachs, “You just need to add some wing angle. But that increases drag, and I, as the project manager said, We don’t need both. Everybody who knows a little bit about aerodynamics knows that’s quite difficult to reach, but that was the question we gave to Francesca.”
Maximal gains
The answer has been revisions around the front lights and air intakes at the front with active grille shutters, the rear design and the operation of the active rear spoiler as well as, and crucially, the new aero 21-inch wheels with specially developed Pirelli P-Zero tyres. The combination of which has seen the Taycan Turbo S gain more than 40km on the WLTP test cycle, it now being a 0.22 car, while in Range mode, with it being 0.26 when in its Sport + mode (that down from 0.29 of the original car in Sport+). The revisions have reduced lift on both axles at speed, aiding stability and adding the dynamism required.
Cogotti is quick to highlight that a good portion of the gains found were thanks to the work of the thermodynamics team, who via software developments have reduced the need for the active shutters to be open. “If it’s not needed from the car to open the shutter for a thermal reason, the Turbo S is able to drive up to its 260km/h top speed with the shutters in their closed position,” she says. “That optimization of the software keeps those shutters closed for as long as possible because the delta of an open shutter has a really big impact on the drag.”
Another key area is those wheels, the team achieving big gains thanks to the new aerodynamically optimised wheels. The original Mission E 21-inch wheels with standard performance tyres were not yet optimised 100% in aero on the previous Taycan. They created separation of the air down the side of the body, that in turn generated a bigger wake behind, increasing drag. The new wheels improve on that significantly and their fitment is instrumental in the aero gains made on the Turbo S. Their design was optimized for an easier transition between the tyre and the wheel by having a smooth flange rather than a sharp one as on the previous wheel and tyre package.
With those in aerodynamics sharing the same building as their design colleagues, Cogotti notes that since the adoption of electro mobility such is the need for efficiency that, “The cooperation with the designers has improved and we work together to get more efficiency. There are simulations, and we work together in the wind tunnel, but they’re understanding when we have requests and usually, we find the right compromise.” Naturally, there are other compromises due to necessity. There was a small negative impact on the aerodynamics due to a request from the production/maintenance side of the business requesting the under-body panels of the original be less extensive, as they took too long to remove while servicing. All of which makes finding the gains elsewhere even more important.
Up on the downforce
With the Taycan Turbo GT the need for efficiency gains would be less so, as the focus here was the aerodynamic balance, reducing front axle lift of the non-GT car. Going further again with the Taycan GT with Weissach Package, the goal was all about the outright performance gains that can be made by creating even greater downforce.
With the Weissach Package car the changes are extensive but follow pretty much the pre-described route to gaining downforce. There’s a fixed rear wing positioned high on struts out on the boot lid, while a completely revised front splitter with a pronounced lip, and changes to the underbody aerodynamics assist in the team’s goal of generating downforce. The spoilers fore of the front wheels have been removed and there’s now a front ‘diffuser’ in their position, the air directed via vanes underneath to significantly improve the acceleration of the air under the car, creating enough pressure to gain downforce. At its 305km/h top speed there’s up to 80kg of downforce on the front axle, with the rear having up to 140kg. That is a sizeable increase over the Turbo GT, which without the diffuser on the front axle develops up to 30kg of lift at its same 305km/h top speed, with 30kg of downforce on the rear axle.
It’s the Turbo GT Weissach Pack’s aero gains that contributed significantly to it setting at the Nurburgring. With Porsche’s test driver Lars Kern, it set a production EV lap time record of 7 mins 07 seconds, cutting a not insignificant 26 seconds off the previous best lap he set in a Taycan Turbo S Sport in 2022. As a demonstration of the effectiveness of aerodynamic revisions, this new lap time is a convincing one, but it’s the gains made elsewhere in the model range that really make the biggest impact. The work Cogotti and the team in the Porsche’s wind tunnel as well as the designers and engineers elsewhere in Porsche gain major efficiencies to the benefit of all.
The Wind Tunnel
“This is one of the most expensive and most complicated test facilities within Porsche, and one of only a few wind tunnels of its kind,” explains Max Ganis, Head of Aerodynamics and Aeroacoustics, Porsche. Built in what’s described as a Göttingen design in a closed loop, the wind is generated by a fan featuring carbon fibre blades which are spun by a motor of around 7 megawatts. In an hour of running that motor will use enough power to allow a Taycan to travel over 30,000km – just as well its purpose is creating efficiencies in the Porsche line-up to offset that.
Those efficiencies are typically measured at around 140km/h, but it’s a Porsche wind tunnel, so the maximum velocity is as high as 300km/h. There’s not just one belt for testing, but two. For production cars there’s a five-belt system, with one for each of the car’s wheels, and the fifth running underneath the car to recreate the road moving beneath it. The second belt choice is a single one stored within the building. A crane is needed to lift the belts out as they weigh around 20 tonnes and switching them overtakes about 3 hours. “The five-belt system is more precise for testing road cars,” says Ganis. “The one belt system gives us a better understanding of the motorsport characteristics of the cars – though we have a lot more difficulty fixing the cars with that and therefore generally we tend to prefer using the five-belt system.”
The five belt set-up also allows quicker changes for things like wheels, which enables the wind tunnel team to turn around more homologation tests for certification, of which there are many. Those belts are housed independently within the wind tunnel, with their own foundations, this isolating them from any vibrations from the tunnel. Similarly, too, the fan is housed in its own isolated structure.
“What you see also on about this wind tunnel, it’s a fully certified acoustic wind tunnel as well. You can see over there we have this massive array that we then take out. It’s a massive microform array that then gives us the possibility to do a 3D beam forming analysis of the different points of the car that then constitute sources of possible noise,” highlights Ganis. As well as the generation of the wind, the tunnel requires significant energy to retain a constant temperature, doing so allowing repeatability of measurements, which Ganis says: “for the balance, which is very, very precise, we need to keep a stable, constant 25 degree temperature.” That again draws significant energy, with Ganis saying that as part of the company’s goals of creating a zero impact facility there are steps being made, there are solar panels on the roof, and the cooling tower is open, which reduces overall energy demand, but it’s still some way off offsetting its total consumption. That a forgivable, and necessary compromise as it’s a proven, effective tool in creating efficiencies elsewhere, which will have a far greater impact overall.
