31. August 2011
According to John Bednarchik, the 2013 Malibu is the most aerodynamic midsize Chevrolet to be produced in the 100-year history of Chevy. He should know. He’s the Malibu lead aerodynamic engineer. That’s him on the right.
On the left is Suzanne Cody. She’s an aerodynamic development engineer who is working with Bednarchik on the project. Although this photo doesn’t show it very well, her hair is streaked with what can be described as “General Motors Blue.” Really.
Those two are standing in the GM Aerodynamics Laboratory at the GM Tech Center in Warren, Michigan. According to Cody it is the largest automotive-dedicated closed-loop wind tunnel in the world. What this means is that when the 4,500-hp variable speed electric motor cranks up and begins spinning the 43-ft diameter fan with 6 balsa-tipped spruce blades at up to 270 rpm, creating a wind speed of up to 138 mph in the test section (where Bednarchik and Cody are standing), the closed-loop design helps the efficiency of the system, which operates 24 hours per day, at least five days per week.
(In case you’re wondering, the silver pool cue-like object that Bednarchik is holding emits a vapor that is actually created by a food preservative that is sometimes used to watch the airflow over the surface of a vehicle. There are also other visual cues like ink on the surface and tufts of yarn attached to it. John Carfaro, Malibu exterior design director, and a long-time veteran of working in the wind tunnel, says he prefers the yarn approach.)
The coefficient of drag (Cd) for the 2013 Malibu is 0.29. It is bested by the Chevy Volt, which is 0.28. But learnings from the Volt were applied to the new Malibu with some significant benefit, because the current Malibu has a coefficient of drag of 0.35, and lower is better.
It is worth noting that in order to get there they made design modifications that are measured in “counts.” Each count is a 0.001 Cd improvement. So, for example, here are examples of what they did to achieve counts:
· 10 counts: rounding front corners
· 7 counts: closing the upper grille section
· 7 counts: using active shutters in the lower opening
· 5 counts: using a front air dam below the front fascia
· 10 counts: positioning tire deflectors on the edge of the front fascia just ahead of the tires
· 10 counts: putting underbody panels over approximately half of the underbody
· 2 counts: integrating a decklid spoiler to provide a crisp trailing edge for the rear of the car
What’s the role of giant wind tunnels in the age of computational fluid dynamics (CFD)? Well, that extensive use ought to give you a clue. That and the fact that GM designers and engineers use CFD extensively. Cody points out that thanks to the location of the tunnel—connected via underground passage to the GM Design Center—that if there is an area of a clay model that’s being tested for aero, if there is a particular area that needs to be modified, she can readily get a sculptor to shave the clay and then do a test, with the whole thing taking minutes, not the hours that running a new CFD would require. “We have the capability, so. . . .”
Look at that picture of Bednarchik and Cody again. Those two are serious. Committed to the task.
He spends some of his off hours in a high-intensity strength and conditioning program.
She is a member of the Bath City Roller Girls roller derby team (her game name is “Shovey Camaro”).
Real people who are really committed to doing what they do. On the job and off.
And the 2013 Malibu—and the other cars and trucks that go rolling through their aero lab—will be better for it.