Fuel injection
Fuel injection allows a precise amount of fuel to suit the amount of air flowing through the engine; making it more efficient. Fuel injection is also used to regulate the horsepower rating of the stock cars; making the sport safer, providing for more fuel efficient vehicles, in addition to cleaning the environment for the spectators in and out of the race. There are more than 150 different adjustments that Sprint Cup Series crew chiefs can make with fuel injection; as opposed to 24 different adjustments with a carburetor. Engineers and mechanics that are employed in NASCAR will develop methods to keep the top speed of the vehicles at less than on the longest tracks of the circuit like Talladega Superspeedway and Daytona International Speedway.