Engineers spend countless hours in wind tunnels and CAD programs optimizing the flow of air around and through a vehicle–particularly in high-performance cars like the Acura NSX. But without lines on a computer screen or carefully controlled smoke machines in a wind tunnel, how can the finished product demonstrate how effective this engineering is outside of a controlled environment, in the real world?
Jason Fenske of Engineering Explained does a good job explaining how the NSX's aerodynamics work using simpler methods than a wind tunnel. A smoke grenade doesn't provide the clean lines of smoke you get in a wind tunnel, but following a lead car with an active grenade still demonstrates how air flows into, through, and around the car.
As one would expect, the front grill sucks air into the front of the car through the primary radiator for cooling. This air then exits through hood vents and flows under the side mirrors, around the side of the car, contributing downforce in the process. After being cooled outside the car, the air re-enters through scoops ahead of the rear wheels to flow through the intercoolers, then exits above the rear diffuser.
Some air that enters the front of the NSX is diverted to cooling the front brakes. This normally causes turbulence around the wheel well, but additional air enters the front corner scoops and forms a cushion of clean air that preserves clean airflow around the front wheels. In the rear, the subframe is hollow and pulls air flowing underneath the car to bounce off the suspension onto the brakes for cooling.
Another method to more clearly demonstrate aerodynamics around the NSX is to use flow visualization paint. Formula 1 teams use this on testing days to help them optimize aero settings for each particular track and driver preferences. More like colored water that sticks to the car, after a spirited drive, the paint shows the path the air took at speed. Straight lines are good, since they indicate free, unrestricted airflow. Swirls happen where turbulence occurs. Sometimes this is okay, but in many areas, it is not, particularly where you want air flowing smoothly over the body of the car.
Jason Fenske goes into greater detail and does a good job explaining the process and mechanics of airflow across the Acura NSX. It also looks like great fun playing with smoke bombs and paints around Acura's latest supercar.