How the Volkswagen I.D. R Pushes the Aero Envelope for Pikes Peak
Racing above 9,000 feet means there's no air, so designers have to approach the aerodynamics in a new way.
Volkswagen will compete in the Pikes Peak International Hill Climb this June, where it will field its first factory entry in decades, the I.D. R will climb to the 14,114-foot summit.
The I.D. R is a prototype electric racing vehicle built specifically to slay the 8:57.118 electric course record, set in 2016 by Rhys Millen in the eO PP100. Its 680 horsepower is put to use through dual-motor, torque-vectoring all-wheel drive, allowing zero to 60 mph in 2.25 seconds, and a top speed of 149 mph. Hill climbs tend to favor acceleration over top speed, hence the I.D. R's emphasis on the former.
Pikes Peak in particular demands extreme aerodynamic setups due to the high altitude at which the race is run, stretching from the start line above 9,000 feet to the 14,000-foot peak. Before one can even consider how to account for the lost downforce, the cooling question must be answered. Lower air density slashes the efficiency of any air-cooled system, and the inability to use a wind tunnel to replicate this posed a challenge for Volkswagen.
"We could not manage this solely with the data from the wind tunnel, where it is not possible to recreate the thin air," stated Volkswagen Motorsport's Technical Director, François-Xavier Demaison, in a Friday press release on the I.D. R's aero development. "The simulation was a great help in determining the dimensions required for the cooling system."
Fortunately, that's where computational fluid dynamics, which is often used in advanced aero engineering, came to the rescue. Likewise, with cooling solved, attention could be directed toward slimming drag and fattening downforce.
"The low air pressure up there means that the aerodynamic conditions are different to those at a racetrack on flat land," said Demaison. "For this reason, we concentrated mainly on achieving optimal cornering speeds. The entire chassis is designed to generate as much downforce as possible, without causing too much aerodynamic drag."
In an email to The Drive, Volkswagen spokesman, Mark Gillies expanded upon the I.D. R's aerodynamic philosophy and how it differs from a circuit racing car.
"Basically, the Pikes Peak car trades off drag against downforce—the speeds up the hill are not that high, so getting the wings and underbody to generate downforce are worth some additional drag," explained Gillies. "Of course, the higher you go, the thinner the air, and the lower the drag, so there is also a [trade-off] there."
"If you were to go to a high speed road course, you would run much smaller wings and would likely run a longer nose and tail—think Porsche 917LH for Le Mans and 917K for Brands Hatch."
Volkswagen confirmed to The Drive in April that the I.D. R's aerodynamics were developed in part with the expertise of Porsche Motorsport, with Friday's press release confirming the aid of the Porsche Development Center's wind tunnel (seen below) in Weissach, Germany.
"The altitude on Pikes Peak means that the air we are driving through is on average 35 percent thinner," stated Willy Rampf, former Sauber Formula 1 Team technical lead, and consultant for the I.D. R project. "As a result, we lose 35 percent of our downforce compared to a racetrack at sea level. The huge rear wing allows us to compensate for some of this lost downforce. The imaginative aerodynamic development means that we will still achieve maximum downforce greater than the weight of the car during the hill climb."
Volkswagen confirmed a combined driver-car weight below 2,425 pounds, pushing downforce levels at race altitude beyond 2,200 pounds.
Limited development time (the I.D. R was greenlit in August 2017) meant rapid component prototyping was crucial to the car's refinement on such a short time frame, forcing heavy use of 3-D printing, according to one of the project's computational fluid dynamics engineers, Dr. Hervé Dechipre.
"We printed about 2,000 parts," explained Dechipre. "In doing so, we saved a lot of time."
The Drive emailed Volkswagen for more information on the unique challenges presented by high altitude racing and its associated preparation and was told that the development team in Germany has gone "radio silent" during its crunch time.
Prior to the race, Volkswagen will ship team members out to Colorado for a private test and media session, which will be attended by The Drive. Stay tuned for interviews and additional details on the project.