We built a portable wind tunnel for measuring EV efficiency and will be used to calculate the drag coefficients of Tesla and Chevrolet EVs. It sticks on the car windshield using suction cups. Pitot tube based anemometer.
Jack had two choices to place the portable wind tunnel at mid ground level near the front air intake or place it on the roof.
He said: I personally think that the mid ground level is the most accurate but it sticks out there and I was afraid of damaging it was just easier to place it on the windshield.
He then found a little difference between the GPS speed and wind speed if drove it during the early morning hours on flat ground with a little turbulence.
He was able to back calculate the Drag-Area and using the factory area and ODBII PIDs, get within a few percent of the factory number of Cd=.308. The number was .311. The PIDs are comprehensive and highly accurate. used a tire model for LRR tires.
Next is the Model S.