Advise on underbody pan for Civic.
 

I took some pictures of the underside of my Civic DX. The front of the car seemed a lot more chaotic than I had imagine.

I have a few concerns.

- I don't have an even distribution of attachment points.
- I also have to deal with the oil pan and exhaust/catalytic converter right near the axles.
- The mid-section of the car is fairly smooth except for the exhaust pipe which protrudes lower.
- The back portion has a lot of hollow cavities.

I'm trying to think of ways to put the pan close enough to the car but not so close that it'll touch the cat converter and oil pan. What do you all suggest?

On my civic to do that majority of the mid section of the car, one sheet of 4' x 8' Coroplast was perfect. Split the Coroplast lengthwise so you have two sheets that are 2' x 8'. Remove all the plastic screws that hold on the bottom of the side skirts. Then you can slide the Coroplast sheet in between the side skirt and the underbody. Trim the length from the 8' to about 6' so it is the same length as the side skirt. Position the Coroplast so it comes up to the edge of the tunnel in the Unibody of the car, then use self taping machine screws ever foot to secure the Coroplast to the underside of the unibody. Then poke a hole through the Coroplast that is sandwiched between the unibody and the side skirt so you can re-install the plastic screws for the side skirts. Thats about all the further I made my under pan. The front is going to take one of two routes....Remove the factory under pan and create one yourself, or trim the curled edge from the factory pan and add an extension to it. For the rea of the car, you can order a factory under pan from a VX model and fill in the drivers side "parachute" with that piece.

The underside of my CX was similar to yours except it didn't come with an engine underpan. I cut 3 pieces of Coroplast to fit under my car. One piece ran from the right side front of the car (bolted to the bottom of the front bumper plastic) and ran back to where the exhaust pipe cuts over to the right rear wheel well. It spanned from the edge of the central tunnel to the plastic side molding (tucked up under it) and the midsection portion of the piece was attached similar to TomO's method, except I drilled and tapped 8-32 screw holes into the frame or through plastic and frame on the side moldings. The section under the engine was secured on the outside by the coroplast folded up into the inner sides of the front wheel well and screwed onto the frame where I could reach it or nut and bolted to the rubbery material in the wheel well where only that was available. The inside edge was attached to the frame and extended the line of the central tunnel to the front bumper. The 2nd coroplast sheet mirror imaged the 1st sheet on the left side of thecar except it continued back for its full 8 foot length and widened out as it followed the curve of the exhaust pipe near the rear wheels. The 3rd coroplast piece covered the area under the gas tank to the rear bumper and over(under)lapped the 2nd piece where it met it. Since there weren't many convenient attachment points around the gas tank, I bolted on a section of 1/4"x1" aluminum bar just in front of the tank to provide coroplast/flashing attachment points. This 3rd coroplast piece was attached to the bar, the car's frame, the inside of the left rear wheel well, and the underside of the rear bumper and was cut to clear the muffler. Next I took a 2 foot wide roll of aluminum roof flashing and ran it from the front bumper back along the central tunnel to cover the exhaust sections that were too hot for the coroplast. A 2nd strip of flashing was needed to cover the section where the exhaust pipe curved to the rear wheel well. This underpan was been in place since April 2006. To change engine oil, I drop the front part of the pan to expose enough of the engine to work on. Although slower to install than self-tapping sheel metal screws, I went with drilling and tapping because the tap oil protected the tapped hole from corrosion and the screw can be removed and installed many times without worry of stripping the threads in the hole as is the case with sheet metal screws. Also the tap is useful for lining up the holes in the coroplast and frame when installing screws when initially installing (or when reinstalling after taking the car to the garage for major service) the coroplast.

Materials list:
(2) 4'x8' coroplast sheets
(1) 25'X2' roll of aluminum roof flashing
drill and tap for 8-32 treads
A box each 8-32 x 1/2" and 8-32 X 3/4" screws
Some 8-32 nuts and #8 fender washers
Duct tape (to seal the underpan seams)

Thanks for your responses. They help tremendously. I take it that the exhaust pipe running down the middle of the car was left uncovered for both of your cars?

As I explained above, my exhaust pipe is covered by the aluminum flashing, the only part left partially exposed to the wind under the car is the muffler.