How this “doughnut engine” could reduce the prices of future electric cars

While manufacturers work mainly around batteries, key elements for tomorrow’s electric cars, making them both more ecological and more efficient, we can quickly forget that electric motors also have a role to play.

Electric motors are often integrated into the front or rear axles, but also for some high-end models directly into the wheels. And precisely, it is an in-wheel electric motor that interests us today, an innovation presented at CES 2025 by Donut Lab.

The company has unveiled its second generation of in-wheel electric motors, a motor promising impressive power and torque with minimal weight, while adopting a unique ring-shaped (or donut, as the car is named) design. the company indicates).

Soon the democratization of the electric motor on the wheel?

Today’s electric cars largely inherit the architecture of thermal cars, with motors housed in the chassis and connected to the wheels via a transmission system. Electric motors integrated into the wheels move essential components within the wheel arches. This frees up space in the passenger compartment, and therefore increases habitability or even the space dedicated to the battery..

But these famous motors integrated into the wheel are not devoid of all criticism, starting with their often substantial weight, which has the effect to increase the unsprung masses. This will have a greater impact on driving comfort, handling and braking performance, which could force manufacturers who use this engine to work on more sophisticated elements and, therefore, which could cost more and be as heavier.

Donut Lab’s second-generation motor fits into a 21-inch wheel and delivers up to 630 kW (845 horsepower) and 4,300 Nm per unit. Impressive figures, but remember that this torque is measured differently from more conventional engines, which often benefit from multiplication via a gearbox. In other words, you won’t have production cars with 4,300 Nm of torque.

The real advantage of this engine lies in its weight. With only 40 kg per unitit is approximately three times lighter than a traditional electric motor. Associated with the removal of numerous components, starting with the classic transmission system, this weight gain could reduce the total mass of the vehicle and, consequently, increase its autonomy. But this adds 40 kg, or even 80 for a car equipped with two electric motors at the front wheels, to the unsprung masses.

Savings and increased flexibility

Donut Lab also claims that its engines are 50% less expensive to manufacture thanks to the removal of around 120 parts. This could result in more affordable electric vehicles in the future.

The integration of motors directly into the wheels opens up new possibilities in terms of design, which is why electric supercars sometimes have silhouettes that are futuristic to say the least.

The space gained can be used for additional batteries, more spacious cabins or innovative aerodynamic solutions.

Note that the Kia-Hyundai group is also working on a wheel-motor system, but integrating suspensions. For its part, Donut Lab does not communicate any marketing date, nor any customer who has signed up to this innovative solution.