Why Did You Guys Do That?

By Ed

As, I started to explain the other day, we created this one-off 40-percent scale CTS-V to do what we believe to be the first-ever moving ground plane aero test for a production car.

It’s hard to put this into non-technical terms, but it was a nice advantage to have done this for a super high-performance car. This was us adopting a technique from racing. Aerodynamic testing takes on other dimensions for cars with these types of elite capabilities. When you have the tires really moving and the car “in motion” on a moving ground plane, we can pick up slightly more realistic data for things like how air moves underneath the car at speed, or how air flows through for brake cooling, or even a bit of data for the aero thresholds at very high speeds. Many of these things are of course also tested in “real world” settings on tracks. But having a preview of those conditions early in the process is something we wanted to take advantage of at this very unique facility. Thanks to the guys at ARC, a great facility.

Aero Scale

By Ed

This photo records a little piece of history. CTS-V was the first production car we know of to utilize a process called “moving ground plane aerodynamics testing.” Traditional automotive wind tunnels (of which we have several) send large amounts of air at a static car (or prototype of a car, such as a clay or fiberglass model.) A moving ground plane takes it to another level, as it “moves” the floor underneath the car, rolling the tires and replicating the conditions of actual driving. It’s sort of like a wind tunnel combined with a very high tech treadmill, so to speak. This is a technique previously reserved for testing of advanced race cars.

This was done at a state-of-the-art facility called the Auto Research Center in Indianapolis that is affiliated with racing and engineering leader Adrian Reynard of Reynard Racing (famed for open wheel racing chassis development.) And that is the overwhelming emphasis of this type of testing, Indy cars and other race engineering activities (not surprising that this happens in Indiana!)

Anyway, this required us to create a 50-percent scale CTS-V prototype made mostly of carbon fiber, which is what you see in the photo. This scale model is different from any other we’ve every used, as it had real operating tires and suspension, all built to scale, enabling it to run through the moving ground plane test. More later this week on what we did there, and why we did it.