Do wheel skirts really work?

[MetroMPG]

Thanks for the info, D.A.

Shall we assume from your name & post that aerodynamics are an interest?

[Dynamically Aero]

Originally Posted by MetroMPG

Shall we assume from your name & post that aerodynamics are an interest?

That would be a safe assumption.



Thanks, trebuchet03 and rh77.

[trebuchet03]

What an awesome first post

[rh77]

Originally Posted by trebuchet03

What an awesome first post

I say...

An official introduction is in order.

Cheerio...

[repete86]

Also, these little pieces of plastic in front of the wheels only cost a few cents while a side skirt that needs to be designed to attach and detach yet still remain secure will cost much more.

[The Toecutter]

The effect is present, but small. It also depends upon the car.

From the book Aerodynamics of Road Vehicles, edited by Wolf-Heinrich Hucho, page 166:

From a series study on 14 passenger cars Cogotti deduced that flush panelling of the outer wheel naves could result in a drag reduction of ΔCd = -0.009 +/- 0.003. Inclusion of the wheel and the wheel opening in the vehicle contour allows a certain degree of design freedom. Of course, both the tyre bead and secondary recesses h1 and h2 must be selected so that the body is affected as little as possible.

Covering the rear wheels reduces the drag only on streamlined vehicles, and is effective only when the flow is attached upstream. On vehicles designed for extremely low aerodynamic drag (so-called concept cars) a 'spat' which moves with the steering may also be fitted over the front wheels, or, in more advanced cases, the body shell could flex with the steering motion of the front wheels.


Basically, it would be a good guess to expect about a .01 reduction from adding skirts to a streamlined car that doesn't have them, and little to no effect from a non streamlined car. May explain theclencher's lack of statistically significant results, while metrompg and basjoos had very noticable results.

A lot of aeromods seem to be cumulative or rely on other mods being adopted beforehand before they become functional.

I also recall reading a few SAE papers where the change in results of wheel skirts varied from 0.00 to 0.03. So, make of this what you will.

This car was made in 1999 and got 70 MPG. Why the heck is it not on the road. Looking at it you would think that it was just another sedan. Ford blew it on this one. Same space as the Taurus but 2400 pounds.

Ford developed it for the PNGV project, where our government gave them hundreds of millions of our dollars in welfare handouts to develop an 80 mpg midsize car with a cost penalty under a few thousand dollars.

The catch is, the automakers never had to sell it. The Prodigy, using a low drag composite body and diesel-electric drive got about 70 mpg, 0-60 mph ~ 11 seconds, cost penalty on par with that of a Prius.

But why sell a 70 mpg midsize car when selling an SUV will yield much higher profit margins? The consumer can't buy and demand what isn't for sale.

Even a gasoline car with a 2.5L V6 with 150+ horsepower, no fancy hybrid drive, no composite materials, no engine displacement or horsepower reduction, would see about a 30% combined fuel economy increase from that drag coefficient reduction alone(assuming average for midsize sedans about .32), with no meaningful additional cost. (See this article I wrote for details on drag and fuel economy: http://www.evworld.com/blogs/index.c...d=87&archive=0) The other things are just icing on the cake. Taken cumulatively, they would add up in a big way.

[GasSavers_BluEyes]

I definately feel I saw a gain with rear wheel skirts. The car accelerated faster in passing as well plus I saw less dirt accumulation behind the rear tires, so I'm sold. Ditto when adding front wheel aero by filling in the fender gap on my car as close to the tire as I could.
Follow the link in my garage entry to pics of the car and you can see how my prototype mods went on.

[slurp812]

I read somewhere on the net that in the old days of NASCAR just pulling the wipers off was good for 3mph in top speed on the track. Of course they were going much faster.

[omgwtfbyobbq]

Screw expensive instrumentation, from SAE 1999-01-0806.

[red91sit]

haha, oh you sicko!