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Side skirts for aero

I have been working on cleaning up the air flow under my 2011 Mustang track day car. One thing I have been thinking about is adding vertical rubber side skirts between the front and rear wheel openings. I'm trying to keep the air flow under the car clean with minimum turbulence to get the greatest effect from the rear diffuser. The side skirts hopefully would limit the amount of turbulent air from getting under the car from the sides. Rubber is cheap, wouldn't effect the car if it touched the ground and can easily be taken on and off for track days. Has anybody gone down this path? I'm curious if its worth the effort.
 

Boone

Professional Thread Killer
I am no aerodynamicist, but this sounds like time and money spent on what would likely be a minute downforce improvement. If you have an optimized splitter, flat floor, wings and canards, then maybe you could go down this path. Diffusers are pretty much cosmetic unless they are teamed with a flat floor.

Sorry to sound negative. I'm hoping this helps you get the most of your retirement time.
 
30
40
Exp. Type
HPDE
Exp. Level
Under 3 Years
West
When I was very much younger, I had them on a '76 Capri. Other than the cool Wanna-Be race car look I can state that side skirts had absolutely no effect on a streetcar. Maybe would have had a bit more effect if the car were to ever get up to 180-200 mph, but not with the 2.8 liter six that was in it, LOL.

Now that I think about that little car it was a lot of fun to drive. Lowered, Bilstein shocks, Quicker stabilizer bars, all poly bushings, Goodyear NCT tires. It wasn't the fastest thing on the street, but it would hook a mean corner. Oh! yea, and I took the smog pump off of it because that added at least 75 HP!
 
I am no aerodynamicist, but this sounds like time and money spent on what would likely be a minute downforce improvement. If you have an optimized splitter, flat floor, wings and canards, then maybe you could go down this path. Diffusers are pretty much cosmetic unless they are teamed with a flat floor.

Sorry to sound negative. I'm hoping this helps you get the most of your retirement time.
I'm not an aerodynamicist but I am an engineer who has been building drag, autoX, road race and track day cars for over 60 years. One thing I've learned is that going faster is achieved by small incremental improvements in every aspect of the things that can make a car go faster. The air flow off the front splitter is as smooth as you are going to get. The mustang floor is as flat as can be expected on a production car. The only thing that sticks below the floor are my 3" exhaust pipes which run parallel to the air flow. I've done some reading on the subject and the major contributor to turbulence under the car comes from the higher pressure static air being drawn into the slightly lower pressure high velocity air flowing under the car. This turbulent air will negate or minimize the effectiveness of the diffuser. Theoretically skirts should help alleviate this problem but I agree in the practical real world they may do nothing. When I have some free time I may try the skirts as they are cheap and easy to put on or remove. The problem is I have no way of measuring if they have any effect on the performance of the car. Such is the quandary of trying to go faster.
 

Boone

Professional Thread Killer
Everything you say is correct. What you're planning to do is cheap, so no issue with "bang for the buck" here. My point is just not to expect much "bang," but I think you have that figured out.

I apologize if I underestimated your experience level, and good luck on becoming the "Iron Byron" of the racing world. I too wish I could drive well enough to detect small changes I make.
 

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