In the slipstream of Moby Dick: an extraordinary one-off Flachbau model

ATLANTA. Curiosity and intrigue in the sports car scene and the media were certainly piqued when it emerged that Porsche had registered the model designations ‘Flachbau’ and ‘Flachbau RS’ with the European Patent Office in May 2025. Now, the brand is revealing the secret: the reason for this patent filing is an elaborate transformation of a like-new Type 991.2 911 GT2 RS with Weissach Package from 2018 to a rare one-off Flachbau model. A multidisciplinary team of experts from the Sonderwunsch department, Style Porsche, and development engineers from Weissach, Porsche Motorsport and Manthey – worked on the project for almost three years.

"Converting the car to a Flachbau model proved to be very challenging, even though we left the powertrain unchanged, in agreement with the customer,” explains Alexander Fabig, Vice President Product Offering & Individualization at Porsche. “Our aim was to reinterpret the iconic look of the 935 without compromising on safety, technology or road legality. Thanks to thorough lightweight measures, this one-off car now weighs almost 70 lbs. less than before. That may sound unspectacular at first, but the 911 GT2 RS with Weissach Package is a sports model that is already uncompromisingly optimized in terms of weight reduction."

The Flachbau (otherwise known as Slant Nose) body style and the Sonderwunsch program have been closely linked for decades: in the 1980s, Porsche offered a spectacular customized version of the 911 Turbo (Type 930) with redesigned front fenders and pop-up headlights. The design was based on the legendary Porsche 935, which dominated endurance races for years. Between 1982 and 1989, 948 examples of this special version were sold. Even with later conversions taken into account, Flachbau models are still among the rarest variants of the 911 today.

Grant Larson, who is retired from his role at Porsche AG, is responsible for the design of this Sonderwunsch project. His involvement was a special stroke of luck; after all, he had also designed the modern interpretation of the 935 that Porsche unveiled in 2018 at Rennsport Reunion VI to mark the 70th anniversary of the legendary racing car. "The new Flachbau RS is a modern, fitting reinterpretation of the iconic 935 design," says Larson. "In addition to the revised front fenders, a key feature is the staggered headlight arrangement with very narrow LED units."

The color scheme also deliberately plays on tradition and modern reinterpretation: "We have combined Grand Prix White with sections painted matte black and other areas with exposed carbon fiber," Larson continues. "This creates contrast, and the U-shaped contrast element at the front echoes a design feature of the Martini-liveried 935/78 – the famous 'Moby Dick.' The special white tone was developed for this one-off car. A historic 911 in Grand Prix White from the Porsche AG collection served as the reference, which the experts used to precisely match the color shade.

Purist design: the Flachbau body

The exterior reinterprets the legendary Flachbau shape of the 935. The front fenders sit lower and feature slatted louvers that vent the wheel arches and reduce the air pressure within. Due to the new contour of the front fenders, the fuel filler flap and the underlying mechanism also had to be modified. The front bumper has also been completely redesigned. Subtle canards from Manthey underline the aerodynamic performance at the front end.

A specially designed lighting system is used in the place of the standard round headlights. The three LED elements for high-beam, low beam and daytime running lights are arranged in tiers above one another. The individual light units are very slim: the low beam and high beam each measure just under 1.5 inches in height, and the daytime running lights are even more slender at less than 0.78 inches.

The one-off car is painted in Grand Prix White, a traditional Porsche color introduced for the 911 in 1974. Contrasting elements in black provide striking accents against the exterior paintwork. Stripes on the hood and roof are particularly eye-catching. The center stripe and the U-shaped contrasting element are presented in visible carbon fiber, surrounded by Grand Prix White. The aero discs fitted to the rear wheels are also finished in Grand Prix White, while the brake calipers round off the sporty appearance painted in deep black.

The front splitter, in combination with the underbody structure of the Manthey Kit including the rear diffuser, enhances aerodynamics and ensures uncompromising performance. The carbon-fiber aero discs on the rear wheels reduce drag. The new rear wing with S-shaped mounts was inspired by that of the 911 GT3 R rennsport (Type 992) but is almost two inches higher on this car. It can be manually adjusted into three positions to provide different levels of downforce depending on the track requirements. In the ‘High Downforce’ and ‘Low Downforce’ settings, the downforce on the rear axle is two and three per cent higher, respectively, compared to a 911 GT2 RS with Manthey Kit with the wing in the corresponding positions. At a top track speed of approximately 211 mph in the ‘High Downforce’ setting, the Flachbau RS produces approximately 1,221 lbs. of downforce on the rear axle. The wing adjustment and the corresponding position markings are protected by patent.

Spartan perfection: the interior

Before the conversion, red Alcantara, black leather and exposed carbon fiber characterized the interior. 

In the front area of the cabin, as far back as the seats, the same look and feel was retained. Whereas the area behind the seats, much like a racing car, has been thoroughly stripped out.

Porsche removed several comfort elements at the request of the customer in pursuit of weight reduction. The Porsche Communication Management (PCM) system was removed and replaced by a leather-trimmed storage compartment. All components of the audio system were taken out as well. Sound-deadening materials and floor coverings in the interior and luggage compartment were also largely removed in the pursuit of weight reduction.

Instead, many parts are now presented in exposed metal painted in Grand Prix White, typical of race cars. Selected surfaces, such as the extension of the armrest, are clad with carbon fiber trim. The newly laid wiring harness has deliberately been left exposed and is covered only by protective sheathing. To reduce weight even more, individual wires that were no longer needed have been removed.

‘Flachbau RS’ lettering is embroidered on the headrests of the carbon-fiber bucket seats, behind which the stylized outline of the Nordschleife can be seen. On the passenger side, the dashboard is decorated with a gold-colored badge with ‘Sonderwunsch’ lettering and the inscription ‘Werksunikat 2026 – Flachbau RS’ – Factory one-off in German – engraved on a plate.

The conventional mounting points in the body for components such as the warning triangle and towing eye have been removed. These elements, which are mandatory for road cars, are now housed in a practical box that is easy to remove to minimize overall weight if the car is being used on track.

Extensive testing at Weissach and on the Nordschleife

After the fundamental details of the design were defined, Porsche conducted extensive digital validation testing. This included crash simulations and tests to validate the airbag deployment. In addition, detailed structural analysis was carried out, particularly with regard to the anticipated loads on the large rear wing. Finally, aerodynamic calculations were made using Computational Fluid Dynamics (CFD) in order to further optimize the overall design. It was only after these virtual tests had been successfully completed that production of new tooling to manufacture the modified components gained approval.

This was followed by technical validation of the individual components. The new rear wing was subjected to extreme vibrations on a hydropulse test rig, similar to the vibrations encountered – albeit to a lesser extent – during road use. In addition, the experts also tested its static load-bearing capacity.

A total of three test vehicles were built to carry out further validation tests in facilities such as lighting and wind tunnels, as well as during real-world road tests. Numerous test drives at the Mendig airfield, 50 laps on the Nürburgring-Nordschleife alone and endurance tests at the Weissach site combined to simulate a load on the rear wing equivalent to about 93,200 miles (150,000 km) of customer use.

"On the Nordschleife, it becomes immediately clear how cleanly the aerodynamic concept works," says Porsche test driver Lars Kern, who drove the car on the famous track. "The Flachbau RS remains extremely stable and precise even at very high speeds. This is exactly the kind of feedback needed in order to validate such a radically altered body design."

Even experienced prototype hunters and motorsport fans were impressed: when a camouflaged Flachbau test car completed laps at the Nürburgring, videos of the event appeared on social media almost immediately.

About the Porsche 935

The 935 was developed based on the Type 930 911 Turbo, and caused a sensation on racetracks when it arrived in 1976. Porsche won the World Championship for Makes four times in a row with it. It dominated the 12 Hours of Sebring several times, as well as the 24 Hours of Daytona. At Le Mans, it achieved both class wins and overall victories. Few other production-based racing cars have achieved this kind of success. It was primarily the elongated shape of the 935/78 that earned the now legendary racing car the nickname ‘Moby Dick’. Learn more here:

Porsche Raceborn Moments | Episode 4 - The Porsche 935/78 ‘Moby Dick’ (1978)

As part of Rennsport Reunion 6 in 2018, Porsche presented a modern interpretation of the 935. To mark the ‘70 years of Porsche sports cars’ anniversary, a 700 PS clubsport race car was produced in a limited run of just 77 units.

About Manthey

Manthey specializes in Porsche GT models and has been one of the world's leading Porsche racing teams for 30 years. The company, based in Meuspath near the Nürburgring, employs more than 350 people and is managed by brothers Martin and Nicolas Raeder.

Manthey boasts an impressive track record: its greatest motorsport achievements include seven overall victories at the Nürburgring 24 Hours, six class victories at the 24 Hours of Le Mans, eight titles in the FIA World Endurance Championship and victory in the teams' and drivers' championships in DTM in 2023 and 2025.