The first step in any kind of telemetry is gathering information. Naturally, that comes from the car.
The car's onboard computer, a proprietary tool called a Pi System, collects information, such as speed, RPMs, brake position, temperature and location. A Pi System works more or less like an airplane's black box -- except in a race car, the system consists of two black boxes [source: Kushner].
The boxes sit on the vehicle's floorboard. They're connected, via transducers, to critical sites throughout the car -- the steering wheel, shocks, pedals and so on. Sensors measure every conceivable variable -- temperature, movement, voltage. All the information is stored in the boxes.
For real-time broadcasts, cars have an antenna that sends info to computers as the driver circles the track. Telemetry also uses differential GPS, the same system used by the U.S. Coast Guard, to track the relative locations of cars.
Even though computers have brought about incredible improvements to the vehicles, and teams now work with unprecedented expertise, NASCAR has a long tradition of trusting human instinct over technology. Before a race, as many as eight inspectors might go over a car from tip to stern, looking for hidden sensors [source: Kushner].
What that means is that the human driver is still supreme in stock car racing. Says Jeff Gordon, "When I see that green flag, I'm the on-board computer. I'm the telemetry" [source: Kushner].
So what happens before the green flag? Read on to learn how racing teams test and prepare their vehicles.