What parameters are measured in automotive wind tunnel testing?

Wind tunnel testing measures: Drag coefficient (Cd, affects fuel economy and top speed), Lift coefficients (front and rear, affects stability), Side force and yaw moment (crosswind stability), Pressure distribution (using pressure taps), Flow visualization (wool tufts, smoke, oil flow), and Acoustic measurements. A typical sedan has Cd of 0.25-0.35. Engineers optimize using active aero, underbody panels, wheel arch treatments, and mirror design. CFD simulations complement physical testing.