NASCAR Sprint-Cup Series
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CUP: Under The Hood - Aerodynamics
Even a seemingly simple change, like replacing a rear wing with a spoiler, requires a huge effort to optimize...
SPEED Staff  |  Posted August 04, 2010   Charlotte, NC
“Under The Hood Presented by Quaker State” is a series of behind-the-scenes articles about Hendrick Motorsports.
Editor’s note: “Under The Hood Presented by Quaker State” is the first in a series of behind-the-scenes looks at what Hendrick Motrosports does to remain at the front of the hyper-competitive world of NASCAR Sprint Cup racing. This week, Lance McGrew, crew chief of the No. 88 AMP Energy/National Guard Chevrolet Impala driven by Dale Earnhardt Jr., talks about aerodynamics.

There’s really no such thing as a simple change on a NASCAR Sprint Cup car. Change one variable, and pretty soon a dozen things have changed to most efficiently adapt to that change.

And no one is more keenly aware of the effects of change than NASCAR Sprint Cup crew chiefs, the men charged with making their cars perform at peak efficiency every week.

Five races into the 2010 Sprint Cup season, NASCAR decried that the horizontal rear wing and vertical side plates that had been a staple of NASCAR’s new-generation race car since its introduction in 2007, would be replaced with an old-style blade spoiler.

But there was more to it than simply unbolting the rear wing and bolting on a spoiler. Much more, in fact.

“The wing is just a really efficient way of making rear downforce without a lot of drag, where when we went back to the spoiler, it made good downforce, but it also gave a ton of drag to the car,” says Lance McGrew, crew chief for Dale Earnhardt Jr. and the No. 88 AMP Energy/National Guard Chevrolet.
Set to crew chief the No. 5 team and driver Mark Martin in 2011, Lance McGrew (Left) worked with No. 88 driver Dale Earnhardt Jr. (Right) in 2010. (Photo: LAT Photographic)

“The biggest difference in how fundamentally the wing works is the air passes over it, beads up, creates downforce,” says McGrew. “But the side plates are the biggest things that we’ve had to figure out with the car because the side force that the side plates made on the wing, the spoiler doesn’t have that.”

To compensate for the lack of aerodynamic side force that the change from wing to spoiler caused, NASCAR mandated that the rear quarter panels behind the tire be lengthened to recover some side force, according to McGrew.

“In my opinion, the wing made that side force real high on the car, which didn’t go away as much in traffic as being real low with the quarter panel extensions,” says McGrew.

But that’s just the start, McGrew says, which is why Hendrick Motorsports has devoted literally hundreds of hours in the wind tunnel, trying to fine-tune their cars for peak performance.

“It’s just a lot of fundamental differences that you have to account for,” says McGrew. “Everything you figure out — how your NACA duct’s going to be positioned in your quarter windows, or the size of the wheel hub, the way the air works underneath the car with the spoiler vs. the wing — is entirely different. So there’s a lot of things that we had done and tweaked and tuned just trying to make the most available downforce with what you’ve got that we’ve had to completely revisit. There was a lot more — we’ve gone to the wind tunnel lot to try and figure out the best configuration for the spoiler.”

Before the No. 88 ever raced with the new spoiler, Hendrick Motorsports had devoted massive amounts of time and energy getting it right. Since then, they’ve worked just as hard, if not harder, at improving performance.

“We got the biggest chunks of it before we ever came to the race track with the spoiler on and we are continually updating our cars in that direction,” says McGrew. “Some of it’s major changes; a lot of it’s not. You’ll never quit looking. You’ll continue to develop it in the wind tunnel. And we’ll continue to try to optimize the package and figure out the balance for the driver.”

Read more... “Under The Hood Presented by Quaker State”
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