Porsche Flachbau RS is a Factory-Built 935 for the Road

The project started with a 2018 Weissach-equipped 991.2 GT2 RS and took almost three years to complete, involving engineers from Porsche Motorsport and Manthey alongside the Sonderwunsch and Style Porsche teams. Why the extensive timescale and roll-call? The customer insisted on retaining the car's road-legal status. That meant Porsche had to build three development cars and subject the new body and aero package to structural analysis, crash simulations, CFD and wind-tunnel work.

Testing also included repeated runs at Mendig, endurance work at Weissach and 50 laps of the Nürburgring Nordschleife. No official lap record attempt was made, but Porsche test driver Lars Kern recorded multiple times below seven minutes in the process.

The reveal settles rampant speculation as to why Porsche registered the Flachbau and Flachbau RS names in May 2025. Rather than signalling the return of the slantnose as a series-production 911, both were required for this particular commission, which Porsche describes explicitly as a factory one-off.

The new look is the work of Grant Larson, the recently retired Porsche designer also responsible for the modern 935 unveiled in 2018. In addition to the flatter front wings, a staggered headlight arrangement with very narrow LED units takes the place of the 930's pop-ups, while louvres cut into those wings relieve pressure from the wheelarches. Changing the profile also required Porsche to redesign the fuel-filler flap and its mechanism.

A completely new front bumper sits beneath, incorporating Manthey dive planes. Its splitter works with the underbody and rear diffuser from the GT2 RS Manthey Kit, and carbon aerodiscs cover the rear wheels to reduce drag. The broad U-shaped graphic across the nose pays homage to the Martini-liveried 935/78, although here it combines exposed carbon with matt black detailing over the Grand Prix White paint, a treatment repeated along the length of the car.

The rear of the car has more in common with a Type 930 Flachbau than the 935 racer or Straßenversion, save for the enormous 911 GT3 R rennsport-style rear wing. Sitting 50mm higher than the GT3 R's, the manually adjustable wing has three positions and generates more rear downforce than the equivalent Manthey-equipped GT2 RS.

Given Porsche was starting with a car that already used the air to its advantage, refining the aero further meant the gains were inevitably marginal: two per cent in High Downforce and three per cent in Low Downforce. At 211mph with the wing set for maximum downforce, the Flachbau RS produces 554kg of load over the rear axle.

Mechanically, the car is unchanged. That leaves the GT2 RS's 3.8-litre twin-turbo flat-six producing 690bhp and 553lb ft, sent exclusively to the rear wheels through a seven-speed PDK transmission. Weight reduction has continued where the Weissach Package left off, however, with Porsche removing a further 31.6kg from the donor car.

Most of the saving comes from winding back the clock on the interior. Successive RS models have made their peace with usability, but the Flachbau restores the ruthlessness. Porsche Communication Management has gone, along with the complete audio system, most of the sound insulation and sections of the carpeting. Behind the carbon bucket seats, exposed Grand Prix White-painted metal and a visible wiring loom replace the usual trim. Any surplus cabling went the same way. Porsche has even deleted the normal mounting points for the warning triangle and towing eye. Both now travel in a removable emergency box, so the whole assembly can stay behind during track use.

The original red Alcantara, black leather and carbon trim remain across the front of the cabin. The only additions are Flachbau RS embroidery on the headrests and a plaque on the passenger side that rubber-stamps the car's Sonderwunsch status. 

It’s been 32 years since an official road-going Flachbau emerged from Porsche. The company insists the Flachbau RS will remain a one-off. We can’t help but notice two trademarks were registered.