Porsche is at the top of its game at the FIA World Endurance Championship (WEC) at the moment, fresh from securing a clean sweep of the manufacturers’, drivers’ and teams’ titles in both GTE Pro and Am classes. But Zuffenhausen isn’t resting on its laurels, as it has wheeled out a new version of its 911 RSR at the Goodwood Festival of Speed last weekend, in preparation for the 2019-2020 season.

Despite being arguably the quickest car on the grid this past year, the RSR – still based on the 991 instead of the new 992 – has pretty much been redeveloped from the ground up. “Ninety-five percent of the car is new. The only components that we’ve kept unchanged from the predecessor are the headlights, brake system, clutch, driver’s seat and parts of the suspension,” said director of GT factory motorsport Pascal Zurlinden.

It all starts with the engine. Having moved the engine to the middle in 2017 – to the shock and horror of the rear-engined faithful – Porsche has now enlarged the naturally-aspirated flat-six from 4.0 litres to 4,194 cc, making it the largest motor ever fitted to a 911 from the factory. It’s promised to deliver even better drivability over a wider rev range, and depending on the size of the restrictor, it makes around 515 hp.

The boxer engine is pared to a lighter and more rigid six-speed sequential gearbox that delivers faster gearshifts and greater efficiency. The exhaust system has also been revised, now exiting ahead of the rear wheels instead of the back. The shorter ducting reduces weight and allows for the fitment of a larger rear diffuser that delivers increased downforce.

The redesigned exterior has also raised aerodynamic efficiency and stability, improving the use and durability of the tyres – an important factor in endurance racing. Meanwhile, the interior has been tweaked for better ergonomics in response to feedback from the drivers, with an improved collision warning system that helps them spot passing prototype racers even earlier.

Porsche will field two works cars for the coming season, with last year’s Le Mans winners Michael Christensen and Kévin Estre as well as Gianmaria Bruni and Richard Lietz manning the seats. Another two cars will compete in the IMSA WeatherTech SportsCar Championship, with the new car entering the 2020 season. As is customary, the RSR will then be offered to GTE Am teams for the 2020 to 2021 WEC season.