Quote:
Originally Posted by JacobLeSann
I noticed a lot more pressure on the rear (the tufts are flowing much faster), and the tufts spun and fluttered all over the place. I’m not sure if that’s good or bad, but that seems bad.
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Tufts don't show pressure. Even separated vs. attached tufts don't necessarily tell you anything about the pressure.
Deliberately separating the flow behind a roof spoiler on my car dropped the pressure over the rear window.
(Not deliberately) separating the flow on the same window in front of a large Hellcat spoiler raised the pressure, pretty significantly.
If you want to know what the pressure over your rear window looks like with various spoilers, you will need to measure it. Fortunately, that's easy to do. Get a Magnehelic or digital pressure gauge, some tubing, and make or buy a pressure disk. Then
test lots of designs and see what happens.
I would also suggest using a variety of measurements if your goal is to see what a particular change does to the airflow over your car. Tufts will show you one facet. Pressure measurement another. When I thought about fitting a splitter to my car,
I used 4 different tests (steering angle, tufts, pressure, coastdown) to try and get a complete picture.
