No belly pan vs. belly pan

[steffen707]

When I bought my 96 civic hatch it was missing all the plastic that go under the engine bay. I've read that a partial or full bellypan will help aerodynamics; however, I couldn't find a no pan vs some or full pan comparison.

Has anybody tested this? Any links? I'm thinking about making a full bellypan and hoping that it will make a nice difference as I don't have anything there now.

[mcrews]

read the thread in my signature below.
I saw an improvement in mpg

[Sven7]

Belly pan - EcoModder

Expect up to a 5% MPG improvement. Aerohead has posted results from studies that claim up to 15% improvement but I think those are RWD 70's sedans with very bad baseline aero.

[steffen707]

Originally Posted by Sven7

Belly pan - EcoModder

Expect up to a 5% MPG improvement. Aerohead has posted results from studies that claim up to 15% improvement but I think those are RWD 70's sedans with very bad baseline aero.

Thanks for that link, I didn't know ecomodder had a wiki like that.

I found that autospeed link that had a 2 part review on a prius. It was pretty interesting, but I thought the car already had a partial belly pan.

I have a vehicle lift but havn't moved it to my new house from my old shop. I can't wait to test this out and see how much help it makes.

Drafting a semi at 3-5 car lengths I can maintain 65-70mph up moderate hills. Something I would never be able to do without drafting. Hoping that I can do several aero mods to stay in lean burn for a lot longer.

I'm doing the full moon hub trick probably next week. Also, my grill block and WAI would probably work a lot better if I didn't have air blowing around the bottom of the engine bay when driving. It would force the car to suck in a lot more warm air, then new fresh cold air.

[mgmechie]

I have been wanting to do a belly skirt for a while on my '94 Sonoma because it is an aero-nightmare under there, and it rides high enough that plenty of air gets under there. I want it to be an easy install, using the least amount of material as possible (ie not having to do metal around the exhaust and coroplast the rest). So I was thinking of just running window screen material all the way under my truck. My commute to work is 55mph on smooth back country roads (in Kansas so there are NO hills). I figure at this speed the window screen's fine mesh would act just like a solid sheet, and allow air flow when stopped and water to find a way out when it gets in.

What are people's thoughts, have people tried this before? Thanks in advance.

Yay first post to Ecomodder after lurking for over a month!

[skyking]

any pressure gradient at all will push on through a screen like that. It is not just a flow lengthwise, there are differences in pressure under the car. I'd stick to screen only where you had to. In my case, I have a lot of cooling air to deal with so I just left a window under the muffler.

[basjoos]

If you decide to use screen (use metal, not plastic, screen material), you could paint it with a thick paint to fill in the holes in the screen. Use heat resistant paint near the exhaust system.

[mgmechie]

Thanks for the replies. I was planning on using window screen from Home Depot, I can't post the link because I don't have enough posts, but it is fiberglass and the review says that it is really heavy duty, and I have understood that fiberglass is pretty good about high temperatures. I like the idea of thick paint to close the holes, thanks basjoos.

With regards to the pressure difference, would the low pressure zone likely be on the top side of the mesh (closer to the bottom of the truck), especially towards the back end of the truck. I was thinking that if the low pressure was on that side it would only help pull the flow upwards and possibly keeping the flow attached. I had a video shown to me in my CFD class in college (which I can't find right now and it is driving me crazy) where they use a slight vacuum pull from small holes on the top of the foil to keep flow attached to the top side for larger angles of attack. (I liked the programming portion of the class, not so much the theory side so I am not claiming to be even slightly more informed about fluid dynamics than anyone.)

I didn't so much think about the pressure difference though, so thanks for pointing that out Skyking.

Thanks.

[mgmechie]

By the way basjoos, it was your aerocivic that has inspired me to even make an attempt to improve the airflow around my truck. Inspiring, and I can't believe that you only spent $400 on material for your body modifications. Very impressive.

[foxgrockefeller]

Did you get to test out the screen method? If so what kind of improvement and what did you use overall?