Hi @sfioroni,
Actually, you selected the wrong faces for the Layer Addition. This has resulted in a mesh with close to 5M cells when it should be close to 8.2M. Without the layer addition you won’t be able to capture the behavior of the flow close to the car.
When you did this mesh refinement you selected the only faces that should not be selected. Please go back to your mesh and make sure that for the Layer-car mesh refinement you have 22 faces selected. You should not select: MRF_F, MRF_R, Radiator, and Radsupport.
Hope this helps 
Cheers,
Diego