High drafting speeds lead to reduction in spoiler size

TALLADEGA, Ala. -- Precise calculations, computer-animated drafting and wind-tunnel testing are hallmarks of good engineering. But sometimes the predicted results don't match what happens in real life.

And that's the time when you pull out the reciprocating saws and "engineer on the fly." Which is why Tuesday's Sprint Cup test at Talladega Superspeedway could be considered the Case of the Incredible Shrinking Spoiler.

A truer test

Talladega is one thing, but the focus is on Charlotte.

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The 24 cars that participated in the test started the day with restrictor plates slightly larger than an inch in circumference and a 4 1/2-inch tall, U-shaped rear spoiler that included 2-by-12-inch extension flaps on either end. But by the time the test ended, the flaps had been sawed off and the spoiler narrowed 2 inches from its original 64 1/2-inch profile.

So the spoiler with which NASCAR may return in April may not look radically different than the one that was on the car before the advent of the rear wing three years ago. And, according to director of competition John Darby, that's why you need empirical data to confirm or disprove your theories.

"Things on paper and even on wind tunnels look very attractive sometimes, and then you turn the lights on in the room, they have a different appearance," Darby said. "The aero formula and the engine formula we came here with were correct. The relationship between the two probably wound up exactly to what we started with, but at a little bit of a lower scale by the end of the day.

"What we don't have in wind tunnels and what we don't have, even with the best engineers we work with, is the input from the guys who are out there holding the steering wheels. They're the ones actually feeling all the effects. And if they're not comfortable, then we're not going to have a good race, and that's what we're here to do."

Finding the "sweet spot," where the balance between horsepower and drag make for a competitive and comfortable car, can be a tricky formula, Darby said.

"The three things that we work with at restrictor-plate race tracks that ultimately control everything that surrounds the performance of the car are aerodynamic signature, the restrictor-plate size, and rear-end gear," Darby said. "There's a real delicate balance between the three of those that helps us contain the speeds to what we're looking for, as well as keeping the drivers happy." (Continued)