Roadster Track Mode explained: a robot-powered wing and fans that pull 2 g
Track Mode is the Roadster getting ready to grip. The car drops lower, a wing rises at the back, and fans under the floor suck it down onto the road. Tesla says the result is "the best passive downforce package of any road car (approaching F1 levels!)", and the wing is moved by the same kind of actuators Tesla built for its Optimus robot (Drive Tesla, Electrek).
Tesla's Roadster film. Tap to play on YouTube.
What is downforce, and why does it matter?
A car can only turn, brake or speed up as hard as its tires can grip the road. Push a tire down harder and it grips harder. Downforce is air pushing the car down onto the road, so the tires can grip more without the car getting heavier.
Race cars get downforce from wings, which work like an airplane wing turned upside down. The catch: a wing only works when the car is moving fast. At a crawl it does almost nothing.
The moving wing
The Roadster's rear wing changes its angle by itself as the car goes around a track (Tesla North, Electrek). Steep for grip in a corner, flatter for speed on a straight. The motors that move it are actuators made for Tesla's Optimus humanoid robot (Tesla North, Paultan). An actuator is simply the part that makes something move, like a muscle in your arm.
In Track Mode the car sits lower and the wing rises. In Road Mode, Paultan reports, the wing folds away for everyday driving (Paultan).
The fans: downforce without speed
This is the clever part. Fans under the car pull air out from beneath it, and seals along the bottom edge trap a low-pressure pocket. The outside air then presses the car down onto the road (Electrek, Drive Tesla).
Musk said the fans "can pull up to two g's" (Drive Tesla). That means pressing the car down with about twice its own weight. Tesla says that is enough to hold the car upside down, even when it's standing still (Electrek). Unlike a wing, the fans work at any speed, even parked.
The fans have two settings. At low speed they pull the car down for grip. At high speed, passages at the front and back open up to move more air under the car (Paultan, Drive Tesla).