24 hours of Le Mans. Sunday, September 20, 2020. It is 2:07 pm. Works driver Laurens Vanthoor turns into the pit lane with the Porsche 911 RSR. For the last time, the Manthey team fills the tank of the approximately 515 hp racing car with the starting number 92 with fresh petrol. The windows are cleaned again and the driver's bottle is replaced. After a few seconds the car lowers, the six-cylinder boxer comes to life and loudly roars at the mechanics as they leave the parking space. Vanthoor rushes out again on the 13.626 kilometer circuit. Full throttle towards the Dunlop curve, with a lot of momentum over the curbs of the following curves, maximum acceleration through Tertre Rouge towards the first chicane, then brutally on the brakes - over and over again.

While three drivers each share the extremely strenuous work in the cockpit at the 24 Hours of Le Mans, the vehicle has to endure the agony of the toughest endurance race in the world all by itself. In the face of intense competition, people and, above all, machines reach their absolute limits. “Of course, our Porsche 911 RSR is designed for this - we developed this vehicle for extreme endurance runs,” explains Alexander Stehlig, Head of Operations at the FIA WEC. “The components of the car are designed and extensively tested with these challenges in mind. We do a lot of tests on test stands and test the entire package in numerous test and development drives. In theory, a 24-hour race shouldn't be a problem. But the practice sometimes looks different. "

"Our cars have to change around 20,000 gears over the race distance," says Romain Gineste, senior performance engineer in the Porsche GT team. “Don't forget: the race isn't everything - the transmission has to do its job in all practice sessions and in qualifying.” In contrast to previous years, when all teams used the Friday of the Le Mans week to install a completely new one Since 2018, the components have remained in the vehicle for the entire race week. “That was a consideration for us,” says Alexander Stehlig, “because we have to keep an eye on the workload on the team at all times. We swap the parts after the pre-test and leave them in the car until the end of the event. This allows the mechanics on the Friday before the race, in which they have to perform at their best for a very long time and concentrate on the essentials. That has absolutely proven itself for us. Many other teams do the same. "

For the transmission in the Porsche 911 RSR, for example, this operational plan means: Almost another 7,000 gear changes have to work flawlessly at all times - and that in no time at all. With the sequential six-speed gearbox of the nine-eleven, a gearshift takes just 15 milliseconds. The high torque of the 4.2 liter boxer engine thus heaves the racing car from Weissach forward with almost no interruption. “Unlike its predecessor, our current 911 RSR does not use a pneumatic system for changing gears, but an electromechanical one. It works more precisely and, above all, faster, ”explains Alexander Stehlig. "We are really, really good at this discipline," smiles Romain Gineste: Each of the around 28 million ignition processes in the six-cylinder engine should be converted into maximum propulsion during the 24-hour race.

If you brake less, you are faster longer: With this in mind, Porsche developed the braking system of the Porsche 911 RSR. The system is in focus at 13 points per lap at Le Mans. Again and again, the drivers brutally drop anchor in front of narrow passages such as the two chicanes on the famous Hunaudières straight or in front of the Mulsanne curve. In total, they step on the left pedal around 4,000 times with great force during the race. The temperatures of linings and steel brake discs soar to over 400 degrees Celsius at these moments. Sophisticated ventilation cools the system down again within a few meters. “The brakes reach their absolute limit in the 24-hour race. The systems are now so good that we can manage with a brake service at Le Mans, ”reports Alexander Stehlig. The experienced engineer doesn't like to take any risks: “We always play it safe and change the brakes at least on the front axle. It doesn't even cost us a minute because the parts are completely pre-assembled. This works in a safety car phase, for example, without any major consequences for the position in the competition.

The six-cylinder power plant in the 911 RSR, which is tamed to around 515 hp due to the Balance-of-Performance (BoP), is not the only boxer in the car. In the course of the Le Mans 24 Hours, the shock absorbers had to take numerous hard hits without showing any visible cuts. The kinematics have to swallow thousands of vibrations without complaint due to the uneven road surface. “The system is compressed to the maximum 20 times per lap when driving over curbs. The car rebounds with the same frequency. The damper system received a total of almost 7,000 direct hits over the entire race distance, ”says Romain Gineste, citing other impressive figures. Some of the horizontal forces that occur are absorbed by Michelin racing tires, of which only 60 are allowed to be used during the tough 24 hours in consistently dry conditions.