Why This Genius Race Car Was Banned

TL;DR

Nissan's Formula E engineers built a twin-motor flywheel system spinning at 100,000 RPM that stored braking energy illegally efficiently — dominating qualifying until it was banned.

Key Points

• 1.Nissan's engineers exploited a loophole allowing two motors in Formula E. Lead engineer Dr. Chris Vag realized a second motor is a spinning mass that stores kinetic energy like a flywheel, without explicitly violating energy-storage regulations.
• 2.The epicyclic gearbox was the key mechanical innovation. Unlike a differential (one input, two outputs), the epicyclic had two inputs and one output, letting both motors spin at different speeds while staying physically connected — making the system fully legal.
• 3.The flywheel motor had to spin at over 100,000 RPM inside a vacuum. The rotor's outer edge exceeded the speed of sound, generating fatal aerodynamic friction, so the team encased it in carbon fiber and evacuated the air with a vacuum pump through a rotating shaft seal.
• 4.The system delivered three compounding advantages on track. It bypassed the 250 kW regenerative braking cap by storing excess energy in the second motor, then deployed up to 200 kW from the battery plus additional flywheel energy on corner exit, acting as a continuously variable transmission for peak motor efficiency.
• 5.Canopy Simulations' lap-time optimizer found the system was worth 0.8 seconds per lap. The software simultaneously optimized racing line, braking points, throttle, and both motor speeds at every fraction of a second — more gain than DRS on a qualifying lap in Formula 1.
• 6.Canopy's optimization produced a counterintuitive discovery: deploy flywheel energy first, not last. Saving electrical energy for further down the straight allowed the driver to stay flat-out longer, a strategy no human engineer had anticipated before running the simulation.
• 7.Nissan won their first Formula E race in New York while running at only 75% of the system's potential, then were banned. Rival teams lobbied the FIA after four consecutive double DNFs gave way to qualifying dominance; regulators banned the powertrain to prevent years of one-team domination.