VW I.D. R Electric Pikes Peak Challenger, Engineering Discussion

Recently the covers were finally taken off the Pikes Peak challenger from VW. The I.D. R is the fully electric machine optimised to tackle the 19.99km course, with an aero package developed by the small team previously concentrating on the marque’s assault on the WRC.

Full Electric – Why?

More and more we read the growth of alternative fuel sources and powertrains. Reflecting the changes to the road car industry, motorsport has adapted to innovate technologies in this field, for example the meteoric rise of hybridisation performance following the battery technologies developed in the Hybrid LMP1 class of the World Endurance Championship. 

This ‘road relevance’ is also backed up by the application of this vehicle, a short duration sprint with a large altitude gain of 4,720ft (1,440m). The importance of this altitude gain is the way this affects conventional Internal Combustion Engines (ICEs) as they lose performance as the air density reduces; as much as one percent of the available power every 100 metres you climb,” according to Peugeot Sport Director Bruno Famin, on top of a potential loss of 30% of the power at the start line compared to running at sea level. Electric motors do not suffer performance losses at altitude, giving alternative powertrains an edge over the more traditional entrants in this environment. 

Aerodynamics

Before the cover was taken off the car, we could see the silhouette of an aerodynamic monster with an extreme design from front to rear. 

At the front, there’s a large front splitter/diffuser that is raised to feed the underfloor channels and for ground clearance while negotiating the changes in incline (especially the hairpins). Large dive planes are added for extra downforce at the front. 

The opening above the splitter feeds air required for cooling, in this case motors, brakes and potentially the battery pack(s). This air is exhausted out of the sides of the car and above the sidepod area. Small diffusers are added just in front of the front wheels for another extra downforce source. 

The sides of the vehicle have wide skirts fitted to seal the underfloor airflow, keeping its pressure low. The almost 90-degree bend on the outside edge would house a vortex, aiming to seal the gap to the ground. There is a slot, mid-way along this skirt. It is too wide to be a panel gap, so I believe it is there to strengthen the vortex here maintaining the skirts performance along the length of the car. Another possibility is to facilitate its proximity to the ground, it needs to be able to withstand striking the ground, and by splitting the panel, it can flex more readily. 

The wheels from OZ Racing appear to be of lightweight metal construction and with carbon fibre covers fastened on to reduce drag. The wheels are not completely covered to assist the removal of hot air from the brake discs.

Behind the front wheels, the arch is blended to the side of the car to clean the tyre wake and draw out hot air from the brakes and potentially any cooling under the nose. Along the side of the car there are some more winglets generating a little more downforce.

Vortex highlighted in red

The cockpit is small, allowing the rear wing to be fed as clean air as possible. Rear cooling is fed through inlets mounted behind the doors on both sides of the car.

The two-element top-mount rear wing is the widest part of the car, producing a lot of downforce. The flap is at a high angle of attack but is fixed in place unlike the similar wing on the Porsche 919 Evo. The weight addition of a hydraulic system outweighs the drag reduction for a hillclimb car. A little extra downforce is added by small wings on the outer faces of the endplates. These would contribute to the trailing vortices, which already would be expected to be very large for this wing. Should the team require more rearward aero balance, another winglet can be added to the outside of the endplate (under the ANSYS logo). As the performance of a wing reduces closer to its ends, Gurney flaps are mounted vertically on the endplates to reduce the pressure inboard of them, maximising the suction performance of the underside of the wing.

The wing hangs over the back of the car, to provide low pressure above the diffuser exit to help it draw air through at speed. The rear diffuser exits are large, with two main channels. The gap/cavity above the diffuser is the outlet for the rear cooling. The centre of the rear of the car looks to be filled by the rear motor/differential unit. The opportunity for in-wheel motors and therefore a full width diffuser is hampered by the use of large brakes. Deceleration is assisted by the regeneration in the motors. VW claim 20% of the energy required to tackle the course is reclaimed in deceleration allowing for the use of a smaller & lighter battery. 

A vertical fin is mounted behind the cockpit, similarly to those seen on F1 cars and WEC prototypes to offer stability in yaw (while cornering where a slip angle is introduced) The large rear wing endplates and vertical supports would have the same effect, shifting the centre of pressure rearwards.

Mechanical Design

The I.D. R started its life as a Norma prototype monocoque, the same Norma which took Dumas to his 3 recent wins.  The wheelbase is short to enable tight radius cornering. The weight is high for a prototype due to the batteries, VW claims it is “less than” 1100kg. 

To propel this weight, the motors output a total 600 horspower, a conservative number for an OEM backed entrant aiming to push the boundaries of motorsport. For comparison, in 2016 Rhys Millen piloted a car with peak power of 1,600 hp. It is not known for how long the car was able to output peak power (due to cooling/energy use concerns) and what its average power output along the course. This is true HP on the course and will not diminish with altitude. Torque vectoring from the motors can enable this car to save time negotiating the tight hairpins on the course.

The car has a top speed of 149 mph but accelerates from 0-62mph time of 2.25sec. The tyres used are supplied by Michelin and are the same dimensions as LMP1 tyres (31/71 – 18). As the aerodynamic downforce levels are high and there is considerable weight, I would be interested to know if these are the upgraded tyres supplied for use with the Porsche 919 Evo, to handle the higher vertical and lateral loads and supply more grip, or the standard rubber supplied for use in the WEC.  

All things considered that we can see already on the car side, it will be tough to get this machine to the top of the course in overall record time (beating the 8:13.9 set by Sébastien Loeb). VW are publicly aiming for the electric powertrain record, to beat the 2016 time of 8:57.1 by Rhys Millen. What we can say for sure, is that Romain Dumas, a three-time overall winner, is more than capable of maximising this effort against the mountain behind the wheel.