[JulianEdgar]

The Ahmed body, and the lessons drawn from it, are now little used in modern car aerodynamics.

In fact, testing of detailed car models in wind tunnels with a moving floor and wheels has shown that the lessons from the Ahmed body on real cars is quite hit and miss. A good example is the current Porsche Cayenne, that specifically goes against traditional Ahmed body ideas and records lower drag in doing so.

I cover the Porsche in my Century of Car aerodynamics book. When Professor Howell was reading that section, he said that the idea that Ahmed bodies couldn't be relied on to guide car shape was now quite old-hat - he actually mentioned a paper he had written (maybe a decade ago?) that had made that point.

To suggest that you can calculate real-world car Cd figures* from Ahmed body variations, as you appear to do in the post you cite, is completely and utterly wrong.

(*let alone to three decimal places!)