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Old 07-15-2009, 12:59 PM   #1 (permalink)
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Join Date: Jun 2008
Location: Northwest Lower Michigan
Posts: 1,006

Red Car - '89 Chevrolet Celebrity CL 4 door
Team Chevy
90 day: 36.47 mpg (US)

Winter Wagon - '89 Pontiac 6000 LE Wagon
90 day: 28.26 mpg (US)
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Wheel skirts slowing me down?

Awhile back I added some wheel skirts.

A week before the skirts we were getting warm weather and I was getting 37 mpg to work and back every day.

After that it was crappy for awhile and mpg went down. Then it got nice for awhile last week, but I was still only getting 34 mpg to work and 35-36 home. So Monday I took off the skirts. Tuesday morning was a cold 30F and I still got 35, and going home was warm and I got 37. This morning was 45-50F and rain and I got 35.5. Better than I could get any nice warm morning with the skirts on. So I'm leaving them off and reaping the benefits.

It seemed like they could only help. There is a pretty good size area for wind to get trapped in the wheelwell. I extended them past the wheelwell on the bottom to keep the transition shallow. Only thing I can think of is they are about 15" high, and are flush at the top but stick out 2" at the midpoint of the bottom (they are slightly curved to keep the flow smooth). So between both sides that's 30" square inches of frontal area added. Maybe that's what was slowing me down?

I'm thinking of trying something like a half skirt, that only goes down far enough to where it doesn't have to stick out at all to clear the wheel, so no increase in frontal area. However there is also the possibility of a bigger pocket to trap air than with no skirts.

Anybody ever had any similar results with wheel skirts?


Winter daily driver, parked most days right now

Summer daily driver
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