-   Aerodynamics (
-   -   rear wheel skirts... (

malibuguy 02-24-2009 11:57 AM

rear wheel skirts...
for the people who have done them, how much of a gain is there? I'm pondering making some for my tercel...

Frank Lee 02-24-2009 05:37 PM

I have no fe instrumentation... only calc fe tank-to-tank... had skirts and other aeromods on too for quite a while. Couldn't detect change that could be attributed to aeromods.

Not saying it's impossible. Saying results are so small- if any- you'd have a hard time noticing it. And an even harder time proving it.

Do it if it makes you feel good, or are curious. Just don't expect any miracles.

Daox 02-24-2009 07:30 PM

They looks like they're good for around a 3% increase.

Testing grille blocking & wheel skirts: +5.7% improvement -

NeilBlanchard 02-24-2009 11:15 PM


On my xA, the front grill blocks and fog light covers added ~10-12%, and the smooth wheel covers added ~6%, and yes the rear wheel skirts are ~2 to maybe 3%.

malibuguy 02-25-2009 07:38 AM

so it looks like its minor...i'll worry about doing a partial under tray first...that should make a bigger difference

i also need to smooth out the rear from the rear axle beam to the bumper

MetroMPG 02-25-2009 06:53 PM

It depends (TM)...

If the rear wheels are right at the back corner (less bodywork aft for detached flow to reattach on), I think skirts will have a bigger impact.

Also depends on the size of the vehicle's tire/wheel arch gap, the rim design (unless you've got smoothies on), wheel offset...

I agree with Frank: for a normal car, you likely won't be able to see the results over the usual tank-to-tank noise.

Also see:

jime57 02-25-2009 07:09 PM

I have skirts on my Echo and Scangauge instrumentation. I made before and after, two-way tests on a windless day. It looks to me from the scangauge data that the improvement was about 1.4%, near as I could tell. Might be worth more on a Metro, as someone above mentioned. I wouldn't be able to see that small change on a tank-to-tank basis.

Daveedo 02-25-2009 07:27 PM

As for the undertray it seems as though the amount of benefit is dependent upon how high your car is and how rough the underbody is. If your car sits low to the ground already then the undertray may not be that effective. However, the higher it sits and the rougher the underside then it may have more of an effect. That's what I gleaned from reading a VERY long thread on the subject. If I misinterpreted it then by all means let me (and everyone else) know.

PS When doing your aeromods try to do the ABA testing so you have before and after mod baselines for comparisons. :thumbup:Thanks.

Christ 02-25-2009 07:40 PM

One good thing about the under tray vs other mods, even if it's not that great of an aero-improvement, it helps to keep your engine bay clean, which is nice for when you're working in there.

Also, a clean engine could be running more efficiently than a dirty one. The grease and grime kind of holds the heat into the engine, in the wrong places, IMO. I prefer to keep it clean. A bottle of simple green and some water will get you a long way in making the underhood area a little more tolerable to mess with.

winkosmosis 02-25-2009 09:42 PM

Not sure I'd spray Simple Green in the engine bay. It softens some polymers. RC vehicle guys soak tires in SG to make them softer and gripper.

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