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.
Syndicate this site
Comments
How come Cadillac didn't use this type of aero testing on other models before?
Posted by: Classified | February 14, 2008 7:59 PM
As an aero guy I am delighted to see GM putting this technology to use. There is a lot to be gained from a more fully dynamic model. Had GM considered full scale testing? Rumor has it there is a sealed off tunnel somewhere in Pennyslvania that is used for static air, dynamic vehicle testing. Where by the air is stationary and enclosed in a box to remove some of the environmental factors and local air phenomena. I had heard about a race team using such a setup to gain insight into fully dynamic aerodynamics.
I would assume that the scale model results are far quicker then using a CFD method with rotating tire meshes. Though I have to wonder what kinds of things are targeted for refinement in such tests. Downforce, drag, cooling?
I do have a few additional questions regarding the Cd and Cl of the car. As an aerodynamics "designer" I have some concerns about that CTS's squared off looks. Everything I have seen in wind tunnels and tells me that the sharp edges can create either drag or drag reduction depending on how they are implemented. How do the edges effect the CTS compared to a smoother, more streamlined design?
Whether they serve to create turbulence or trip the boundary layers would be one question I'd love to hear an answer on. The question though is whether the CTS's drag and lift coefficiencts are competitive. In the past GM never really talked about these things.
How does the CTS and CTS-V compare to the likes of BMW, Mercedes, Acura, Infiniti, and Lexus etc..
I realize that the market segment for a car like the CTS-V is very unique, but I am forced to wonder about the effects of the CTS body on aero and engines.
As a potential customer the -V is pretty appealing, though I wish it was AWD. But at the same time I can't help but wonder if a tuned version of the V6 DI engine couldn't make 400-450 HP and still get 30 MPG highway. The -V is no doubt the kind of car I want to get as a fun car. I would think the supercharger could be cranked up and closer to 600 HP realized. I also can only imagine that if an AWD system could put 100-200 of that HP at the front wheels to the ground the car would be rediculously fast.
On the other hand the economy and street manors of such a beast would leave me wondering whether I could drive it as a daily driver to and from appointments.
Has the design team considered a turbo version of the CTS V6 as a car just below the -V place? 400-450 HP still places it in a very unique catagory. and if the AWD system could be used, it would prove for a very entertaning car. It would also seem possible to get better economy numbers. If that option were available thats probably what I would want to buy. But for now I'm waiting on details of the CTC and CTC-V, though I can't help but hope for a CTC AWD turbo. Keep up the great work the product line is really coming around.
Posted by: Nate | February 18, 2008 9:10 AM
Class - The short answer is that we didn't do it before because it basically didn't exist for production cars. And, we have our own full-scale windtunnels that in which most aero testing typically occurs - and we'll have some photos and maybe video of that shortly.
Posted by: editor | February 18, 2008 9:54 AM
I'm seriously considering a CTS or CTC in the next year or two (depending on when the CTC comes out). I'd love to see a topic on here regarding the power-terrain, from the engine down to the wheels. I want to know what's there that really makes the CTS stand out. I want to know more about the new DI engines, the New transmissions, and the AWD systems as well as the active stability management. How does it work? How does the system integrate to make the car handle? etc...
I'd also like the opportunity to discuss some ideas I have with someone from Caddillac's CTS division. To be more specific I have an idea I think could really benefit the new CTS and CTC's automatics. I've been hoping to hear from a project manager at GM regarding it. Any chance at that?
In the mean time I'd love to know more about the aero "package" on the CTS. Even some wind tunnel or CFD models would be nice to see.
Posted by: Nate | February 19, 2008 11:47 PM