Wind tunnels for scale size cars are much less useful than they were just 15 years ago. My university sold its wind tunnel for 1/10th scale cars, it was just not that useful compared to CFD. CFD can get you simulations that take into account rotating tires (a big deal on the open wheel cars we were working on). You also don't have to worry about inaccuracies from 3D printing (or however you make the model).