Tesla Roadster Patent Details Active Aerodynamic Fans for Improved Downforce

Tesla has been granted a new patent for an "Electric Car Fan" system designed to keep the upcoming Roadster grounded at high speeds while maintaining low drag. The patent, issued on September 29, outlines a mechanism that uses electrically driven fans to generate downforce regardless of the vehicle's velocity.

What Happened

The patent describes a ducted-fan package located in the rear of the vehicle, typically depicted as a row of four axial fans divided by vertical strakes. These fans draw air from an underbody inlet situated between the rear wheels, route it through ducts, and expel it through a wide outlet in the diffuser. Powered by the vehicle’s high-voltage battery and controlled by the vehicle system, the fans can modulate their output to create downforce when needed and reduce activity at highway speeds to minimize drag.

Why It Matters

This active aerodynamic approach addresses a specific limitation of passive wings and underbody tunnels, which rely on air rushing past the car to generate downforce. At launch, in slow corners, or during hard braking from modest speeds, passive aerodynamics contribute little to grip. Tesla’s design aims to produce necessary downforce independent of speed, potentially improving traction for the Roadster’s claimed sub-two-second 0-60 MPH acceleration and 250-plus-MPH top speed. By adding grip only when required, the system could enhance acceleration rates, decrease stopping distances, and sharpen turn-in without the constant penalty of increased drag associated with fixed wings.

The Bottom Line

While the patent indicates Tesla is exploring active aerodynamics to combat issues at high speeds, it is not a guarantee of a production part. Challenges such as packaging four fans in the rear diffuser, managing noise, and handling potential debris remain. Additionally, similar fan designs have faced bans in competitive motorsport settings due to their effectiveness.