Amateur Aerodynamics

Fences are commonly affixed to racing cars; road cars, not so much. What will they do here? Only one way to find out. Last time , I wrote a little about the difference between steady and dynamic directional stability in car aerodynamics. I only scratched the surface of this very complicated subject, but I was able to find, through testing, the effect of adding rear fins on my Prius’ steady stability (as measured by steering wheel angle) in a constant crosswind.   After finding that I could add an X-gauge to my Scangauge computer that would read the car’s steering angle sensor, I decided to try some more tests to see what various modifications do to the crosswind stability. Fortunately, here in the Midwest it is often quite windy, giving lots of opportunity for testing.   I first spent a few weeks driving around with the STA X-gauge displayed and noted that when the car is going straight down a level, straight road, it reads +1.6 ° (that is, the wheel is turned slightly to the ...

Buckle up, this one's long. After hanging around Ecomodder for years, I had a pretty messed up idea of the function of spoilers because of what I had read on that forum. You might too.   See, the prevailing theory there—based entirely on posts by one forum member who is widely seen as an aerodynamic “guru”—is that spoilers “reach out” to an ideal “template” profile . By so doing, the theory goes on, a “locked vortex” is captured and the airflow above the spoiler follows the “ideal” template line as the air just ahead of the spoiler recirculates. So, simply position a spoiler and extend it until it touches a template profile overlaid on a side-view image of your car and, voil à ! Lower drag—because the spoiler isolates negative pressure in front, higher pressure in the wake behind it, and the outer flow follows the “template” shape. Someone might want to tell this person that the "perfect match" RS spoiler was, according to Burst himself , supposed to be 15 to 20 mm long...