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Old 07-18-2009, 01:11 PM   #10 (permalink)
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Originally Posted by wagonman76 View Post
36.5 going home yesterday with mild headwind on the 8 mile south leg of the trip, 60-70F, and 36.4 this morning with mild headwind on the 12 mile west leg of the trip, 50-60F. This is comparable to what I was getting on similar weather days before the skirts. Warmer days at 70-80F I was getting the 37-37.5 mpg. I had several similar days, even a bit warmer, with the skirts on and still couldn't get any of these numbers. Nothing different going on, didn't have to stop for any more cars or deer or anything. I didn't get new gas when I installed or removed the skirts. As you can see I finally removed the mudflaps, but I did that something like 2 weeks before the skirts. I would think if the skirts were giving negligible effects then I would be getting the same numbers with the skirts on when driving conditions were the same.

Ok so that makes sense, frontal area is not going to make that much of a difference, especially since that extra area was very tapered and smooth and not a blunt flat area.

I did put on an airdam last year. Maybe the diagonal airflow under the car normally exits partially through the rear wheelwells and I was blocking that. Or maybe they were creating turbulence of the air trapped in there, rather than letting it sling out. Who knows. The skirts were definitely not rubbing, they were backed by a welded steel frame of flat bar that would keep them rigid and away from the tire by 1".

The deflectors would be a good thing to try. Just something with a half round front profile to simulate the leading edge of a teardrop?

I'm also thinking of trying a bolt-on extension to the partial boattail. Since that did make a positive difference, I would think an extension would make it better, even if just a tiny bit.
If you can locate or get a hold of an image of Subaru's XT from the 1980s,they have an example of scientific deflectors,developed painstakingly in the windtunnel.A few millimeters apparently makes quite a difference.I tried to respect their parameters when fabricating the rear wheel deflectors for T-100.
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