The 911 RSR, which the Porsche GT Team also campaigned in this year’s Sports Car World Endurance Championship WEC, is a completely new development. The key new feature is the positioning of the engine in front of the rear axle. Thanks to this, the weight distribution was improved and at the same time, space was freed up to fit a larger diffuser at the rear which generates significantly more downforce.
The development of the new 911 RSR began in early 2015. Initially, a small team with representatives from individual divisions was engaged in analysing the lessons learnt from the predecessor model, as well as studying the sporting and technical regulations. From their findings, a new vehicle concept was then tailored to the requirements of modern long-distance racing. Race drivers were also included in the development process earlier than ever before. “The drivers have to feel comfortable in the car,” said Marco Ujhasi. “Only a driver who still feels fresh at the end of a gruelling stint will be able to give the top performance that is needed to be successful in such a tough competitive environment.” See our full interview with Marco Ujhasi.
Engine tests on test benches and race tracks
Thanks to the outstanding baseline engine development for the 911 GT3 R, the RSR engine ran for the first time on the test bench after about seven months, with full-scale endurance runs in less than a year. The test programme for the 911 RSR engine included two 70-hour long runs under different weather conditions, and altogether, the engine withstood over 300 hours of endurance runs. But despite the sophisticated engine test benches, testing on a race track is still critical.
“On the test beds, we simulate maximum stress situations, such as a particularly fast qualifying lap on circuits with maximum full-throttle passages such as Daytona and Le Mans,” said Marco Ujhasi. “Special racing situations, like caution phases or a sudden exit from the pit lane, cannot be simulated on a test bench. These insights as well as impacts on the entire vehicle can only be gained on the race track.”
Extensive wind-tunnel tests
Early on in the development of the aerodynamics for the new 911 RSR, computer simulations CFD (Computational Fluid Dynamics) were carried out. These trials offered the chance to evaluate certain concepts and components without having to actually build a model. Following this, the concepts under consideration were tested in the model wind tunnel, in real airflow. After the model wind-tunnel trials, 80 per cent of the car was completed. The next step for the last 20 per cent was then to go testing in the large Weissach wind tunnel with a running belt. This simulates a race track almost identically as it can replicate entire corners to see how the car will behave on actual race tracks. These discoveries are then fed back into the computer simulation, with the help of which, for example, one can very accurately predict lap times that the car would normally clock on the race track.
The new 911 RSR’s serviceability was significantly improved. Changes to the suspension setup can now be performed much more quickly and easily, and, if necessary, entire elements of the carbon-fibre body can be exchanged completely in a very short time thanks to cleverly-devised quick-release fasteners. A door, for example, can be replaced within 15 seconds, and a front bumper with underbody can be swapped out in less than one minute.
The new 911 RSR is the first Porsche GT race car to be fitted with state-of-the-art assistance systems. Thanks to a radar-supported collision warning system, the so-called Collision Avoidance System, drivers, who are constantly being overtaken by more powerful and faster prototypes, enjoy a better view to the rear. On a monitor in the cockpit, arrows indicate if vehicles are following directly behind. Depending on the colour of the arrows, the driver can tell whether the trailing car is gaining or falling back. Not only does this system work in fair weather, but also in rain, fog and at night. A new safety cage and a new, rigidly-mounted racing seat further enhance driver safety.
Works drivers and teams involved in the development
The Porsche GT works drivers were included in the 911 RSR project at a very early stage. At first, the main priorities were to optimise the correct seating position, the visibility to the front as well as the ergonomics. Drivers must not be affected by a poor seating position, especially at long distance races. Another key factor is the layout of the many lights and switches on the steering wheel and in the cockpit. Every button and switch must be easily accessible and easy to use. As a starting point, a basis was found, but the fine tuning came once the car was put on its wheels. From the first test, the drivers were then involved in identifying weaknesses and further developing the car in conjunction with the engineers.
The drivers were extremely pleased with the result of this very open cooperation. Richard Lietz, the 2015 winner of the FIA Endurance World Cup as the best GT pilot, summed it up this way, “The new 911 RSR is the best GT car that Porsche has ever built.” After the 2017 debut season, in which the 911 RSR was exclusively fielded by the works team in the FIA WEC and the IMSA Championship, Porsche Motorsport is to offer the vehicle to selected customer squads in 2018.
50-hour endurance run on a bumpy track
All of the GT works pilots were given a chance to drive the first kilometres in the new 911 RSR at the rollout in March 2016 at Porsche’s Weissach test track. Extensive tests were then undertaken on race tracks that were selected for a specific development task: suspension setup, tyre and brake development as well as aerodynamic validation. The highlight of the test phase was a 50-hour long run in Sebring. “As far as I know, no other manufacturer has dared to do this,” said Marco Ujhasi. The test on this extremely bumpy race track in Florida, known for the immense challenges it throws at man and machine, ran without any major issues. “Precisely because of the enormous stresses, it was the right direction. This was confirmed at the first two races of the season; the long-distance classics of Daytona and Sebring, where our new car impressed immediately with a strong performance.”
The new 911 RSR is powered by a naturally aspirated, 4-litre, 6-cylinder boxer engine producing around 510bhp, depending on the restrictor. The engine features direct fuel injection as well as a rigid valve drive and is a systematic evolution within the line of Porsche’s normally aspirated motors, which not only meets the demands of a racing engine, but also the requirements of a 911 GT3 for the road. The developers opted for a normally-aspirated powerplant, not only because it saves up to 40kg in weight. Marco Ujhasi again, “A naturally aspirated engine is a highly emotional powerplant for customers of our road-going vehicles, yet it also has the performance potential to meet the high demands of motorsport.”
Other facts and figures
The new 911 RSR consists of 5342 individual parts in total. Of this, the vehicle is made up of 3646 parts, with the engine containing 1282 parts and the gearbox 414 parts. The largest single part is the body, with the smallest component a circlip in the door handle.
Seven 911 RSRs were built by Porsche Motorsport in Weissach for the 2017 motor racing season, two for the Sports Car World Endurance Championship WEC, two for the IMSA SportsCar Championship, and three test vehicles. It takes four employees ten working days to build one 911 RSR.
Since the roll-out in March 2016 to its first race in January 2017 at the Daytona 24-hour race, over 35,000 test kilometres have been covered on various race tracks with the new 911 RSR – that’s more than in the development of any other Porsche GT race car.
Edited by: Glen Smale
Images by: Porsche