Do you want to know? Keep reading.
Cars run on three things: air, fuel, and spark. Spark is pretty simple, so the goal is to get as much air and fuel in the cylinders as possible. The problem is that unrestricted engines combined with aerodynamic developments lead to things like this (Bobby Allison, Talladega 1987).
At that moment NASCAR knew they had a big problem, and that they couldn’t depend on luck to keep the cars out of the stands. So, from that race forward, all races at Daytona and Talladega, the two longest, widest, smoothest tracks capable of generating the highest speeds, are run with restrictor plates.
Originally the restrictor plate mounted directly below the carburetor, reducing the size of the air intake (and thus the cubic feet per minute volume of air) for all cars and therefore controlling speeds because the engines would simply run out of breath. Now that they have switched to fuel injection they place the restrictor plate on the air intake, where it serves the same function.
This leads to another problem. If all cars are essentially limited to the same top speed, nobody can get away. Therefore, the way to go fast is to get behind somebody and let their aerodynamic package break the wind for you. This is called drafting. With that being the most effective way to go fast, the drivers all do it, creating a pack of cars all pushing 200 miles per hour, side by side, sometimes even three or four-wide.
It makes for very exciting edge-of-your-seat racing, but it’s ridiculously dangerous. Almost invariably someone has a problem or makes a mistake and wipes out half the field. This is known as The Big One. Yesterday’s Big One may or may not have been intentional.
So there you go. A really quick primer on racing at Daytona and Talladega and what restrictor plates are.
