YASA builds electric motors that are roughly 20% as thick as a conventional unit and weigh about a quarter as much, yet they deliver three to four times the power density. The Oxford company achieved this by revisiting axial flux motor design, a concept that actually predates the cylindrical motors you find in most EVs today. Their production facility now turns out 25,000 motors a year. One of their prototypes produced 1,000 horsepower from a motor weighing just 12.7 kilograms. The real story, though, is not the headline numbers. It is what happens to the rest of the car when the motor gets that much lighter.
Most EV motors use a radial flux design: a cylindrical rotor sits inside a ring of stator windings, and the magnetic field flows outward from the center. YASA's axial flux layout stacks two spinning disc rotors on either side of the stator instead, so the magnetic field travels straight through rather than looping around. That allows them to eliminate a large chunk of iron called the magnetic yoke, which in a conventional stator can account for the majority of the machine's mass. The materials needed to press the three-dimensional stator segments in this design did not exist until the late 1990s, which explains why a topology invented in the early 19th century only became manufacturable at scale in recent years. Mercedes-Benz acquired YASA in 2021 to develop high-performance electric powertrains, and the motors are now used in Ferrari and Lamborghini road cars alongside future Mercedes-AMG products.
The mass compounding argument is where the numbers get interesting. YASA's engineers explain that saving one kilogram from a motor or battery tends to cascade through the rest of the vehicle, enabling lighter brakes, a smaller battery pack, and a lighter chassis, roughly doubling the initial saving by the time every connected system is recalculated. Strip 100 kg from the motor and the total vehicle weight reduction can approach 200 kg. The video goes further and covers in-wheel motor possibilities, where YASA claims its latest technology can match the power density of a carbon ceramic brake disc. At that level, regenerative braking could handle virtually all normal deceleration on a track, shrinking the physical brakes to a small emergency-stop disc rather than the heavy components used today. Battery packs could shrink correspondingly, and the mass spiral keeps tightening.
Bottom line: YASA's factory tour is a good reminder that the most consequential EV hardware development is not always happening inside the carmakers themselves. If the mass decompounding numbers hold at volume, axial flux motors could shift what a performance EV is allowed to weigh by the end of the decade.