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Old 09-29-2008, 10:48 PM   #1 (permalink)
Master EcoModder
wagonman76's Avatar
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)
Thanks: 8
Thanked 17 Times in 16 Posts
Airdam vs partial bellypan?

About a week ago I decided to remove the airdam and attach a partial bellypan using the same screw holes. Sorry my camera is on the fritz, but it runs from the lower edge of the valence to the engine cradle (lowest part of the undercarriage), about 16". I also took some of what was left over and blocked off about half of the breather openings in the valence.

The results - hard to say. It immediately feels like less resistance, just like when I put the airdam on it immediately felt like more resistance. That makes sense because the airdam hung a tad below the engine cradle and therefore created a bit more profile. However even despite two pretty warm and calm highway drives, it seemed to lose some mileage. Last week we had some warm days and I lost some mileage to work and back too, plus I seem to be doing worse than similar days that were at even lower temperatures. I know the fan isnt running, because the car runs at pretty much the same temperature as usual, and I know where the temp gauge has to be to get the fan to come on and its nowhere close.

Does this make any sense? I wonder if the airdam was pushing up a roll of air to help get the rest of the air over top of the car? Sort of like a pickup with gate up gets better mileage from the roll of air that the tailgate pushes up? It seems counterintuitive, foolishness like saying a parachuter will go faster from the wad of air created by the parachute, but in the pickup case its supposedly been proven.

And if that is the case, it seems that I would really benefit from a good sized false nose that would mimic this roll of air, and reduce any parachute effect.

Has anybody else had any other similar or not so similar experiences?


Winter daily driver, parked most days right now

Summer daily driver
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