This thesis work aims to analyze the aerodynamic aspects of a competition car. In particu- lar, we considered here the Honda Civic 2018, a 5-door sedan of the Japanese house, which competes in the TCR championship, built by J.A.S. Motorsport of Arluno (MI). Thanks to the internship at this company, I was able to observe all the construction phases of the car and understand how a car championship is dealt with in many ways, from the logistic one to the preparation of the setup for the different tracks, to the continuous refinements on the mechanics, on the chassis and on the aerodynamic part.