The software used was the demo version of MicroCFD.
Unfortunately the software does not allow for the parameters (car size, speed, etc.) to be set at the proper levels for the Mini-Z scale, so the results are just illustrative.
Any useful results would require not only setting the parameters right but also using a 3D software and car model, including the detailed geometry of the bottom of the car.
In any case, I'm really sorry I skipped all those Fluid Mechanics classes... I wish I knew how to read the results above.