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Old 05-07-2010, 10:10 AM   #1 (permalink)
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Underbody Trays

First, I'm not willing to make my car look, in my opinion, stupid. I guess in most part I'm form>function lol. Belly pans are out of site and shouldn't be too hard to make. I know they come stock on some civics in the front I just got to check to see if mine has the full one or just a splash guard. My car is a 98 ex civic.

My main concern is the rear. The fast and the furious ricers and the true drag racers all cut holes in their rear bumper to help with airflow since there is a big pocket back there on our cars. I would like to cover this up and will probably be my first aero mod. Can anyone speculate on the mpg increase on adding this?

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Old 05-07-2010, 12:15 PM   #2 (permalink)
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If the air is turbulent up by the engine bay (and it is without a pan), then the air will be turbulent at the rear. Start from the front and work your way to the back.
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Old 05-07-2010, 04:04 PM   #3 (permalink)
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rear diffuser

Drilling holes in the bumper cover has come up before on here. The consensus seems to be that the holes still increase turbulence. You should strive to make things smooth and tapered like a dolphin or a seal's shape. Deezler has built a nice rear diffuser which should reduce lift and reduce drag at the same time.

http://ecomodder.com/forum/showthrea...ad-7868-4.html

If you are going to cut up a bumper cover, this would be a better way to go.
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The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
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Old 05-07-2010, 06:50 PM   #4 (permalink)
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apples to oranges.
Most of those cars are running body kits so there is an extra 1-2 inchs hanging dow in back. I know that was the case on my Q.They cut holes instead of doing an underbelly pan.
http://ecomodder.com/forum/showthrea...q45-11402.html
I ran the underpan edge to edge front to back (with concideration for the exhaust.)
If you really want to keep as stock as possible, that's the way to go.
cutting up the bumper would garner looks....
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Old 05-08-2010, 07:23 AM   #5 (permalink)
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Well, I'll jump in for a first post on this forum. I have a Miata, and recently was rear ended. I trimmed the rear bumper cover to remove the damaged section. Conventional wisdom on miata.net is that the rear bumper acts like a parachute catching air that is flowing under the car. Anyway, after removing the lower section of the bumper cover I can see about a 1 mpg improvement in mileage on the highway, measured with the scangauge.
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Old 05-08-2010, 12:05 PM   #6 (permalink)
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Like I said, form>function. I'm not cutting holes in my bumper. Thanks for the imput and I will be installing underbelly pans!
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Old 05-08-2010, 02:17 PM   #7 (permalink)
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subaru

Subaru published this kind of data from development of the XT.
The info is probably in the Mod-data sticky.If not,I'll dig it out unless someone else has that handy.
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Old 05-08-2010, 04:06 PM   #8 (permalink)
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Trim rear bumper

Quote:
Originally Posted by bossfrog View Post
Well, I'll jump in for a first post on this forum. I have a Miata, and recently was rear ended. I trimmed the rear bumper cover to remove the damaged section. Conventional wisdom on miata.net is that the rear bumper acts like a parachute catching air that is flowing under the car. Anyway, after removing the lower section of the bumper cover I can see about a 1 mpg improvement in mileage on the highway, measured with the scangauge.
Bossfrog, Are you planning any other aeromods to your Miata??
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Old 05-09-2010, 09:45 AM   #9 (permalink)
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Yes, next step is a diffuser under the section I cut out. After that, I'm going to try an undertray. It will probably leave the tunnel/driveshaft open to facilitate cooling to the rear end. After all that is done, I may try some side skirts.

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