DIY rear bumper air shield
 

Purpose is to create a wind shield when changing from a stock style suitcase muffler. This should stop air from getting trapped behind the rear bumper which creates a parachute.

I have the Borla exhaust which drops ~10lbs off the car. I know Borla has there own diffuser for their exhaust but it also adds ~8lbs back on. Negating the weight loss of the exhaust.


For the record I want to make this out of a sheet of Carbon Fiber. I would need a 2' x3' sheet to make. 2x4 sheets are $300 for 1mm thick. Crazy! If anyone can find a sheet cheaper please let me know


For this version I used Coroplast as the plate. I want lightweight,I have no idea how the coroplast will hold up. At least I can transfer the design if I find a better material to use


Materials used all found at home depot
Sheet of coroplast need at 2'x3' to work with
Threaded rods
Hollow aluminum tube
nuts bolts washers, fender washers

Total weight 1.5lbs
weighted everything at ~2lbs then minus everything I didn't use ~.5lbs

Parts on scale
https://i.imgur.com/fXnwoks.jpg

Rods bolted up to stock heat shield brackets.
https://i.imgur.com/XSvBDqP.jpg
https://i.imgur.com/R4TfbBq.jpg

Now showing the aluminum tubes with fender washers giving a solid mount for the shield

https://i.imgur.com/sYcpyM5.jpg

Installed! The plate tucks inbetween the rear stock diffuser and mount. used the stock rear diffuser attachments just switched out the black plugs with bolts. Also cut the rod bar after everything was mounted.

https://i.imgur.com/IAqD7VZ.jpg

An inside view
https://i.imgur.com/RPTeXk9.jpg

Have it up all the way to the rear subframe. Plate sits on top or the LCA bolts

https://i.imgur.com/zfcppPG.jpg

Final pic!

https://i.imgur.com/WcSL1A6.jpg


UPDATE POST 23!!

How much clearance between the coroplast and the exhaust pipe? Like where the exhaust pipe goes through that cut out?

You can see from the last pic about 1/2" around the pipe area. Gave it more room with the coroplast so it doesn't melt. If I can find cheaper carbon fiber I would cut it closer so no air can't sneak up there

Why carbon fiber over aluminum?

WEight

Approximately 1.5 lbs lighter. Is that worth the added cost?

For him it was, nice job Tom.

Carbon fiber sheet at 1mm thick should be lighter and stronger than aluminum. im looking for at least a 2'x3' sheet. Where are you getting your measurements from please source. 1mm thick aluminum might not be strong enough Id have to hold it in my heads to check for flex

home depot has sheets at .019" thickness which equates to about a .5mm I will check those out to give me an idea

You're probably right. I just found the weights of a 2" x 3" by 1mm sheet of CF and AL. 1mm aluminum probably would be too thin, but it doesn't need to really structurally support anything. I'm just bored at work, so thought I would give the feedback.

A 2" x 3" by 0.5mm thick piece of aluminum weighs .783kg or 1.72lbs.
A 2" x 3" by 1 mm thick piece of carbon fiber weighs .875kg or 1.93lbs.

Just using densities of the materials.

Well I read on the ecomodders forums many of them use coroplast to create flat panels under the cars. Although a rock bouncing up could easily punch a hole in it.


Aluminum may be enough I just don't want it to flex crazy if a lot of wind goes through that area. But I don't think it has to be super solid stiff to work. I will test that aluminum sheet when I go to home depot tomorrow. And hopefully its not too heavy.

I don't see any reason to change up what you have now. Looks great and will be just fine on the highway. It's already tougher than the bumper cover.

Any idea what the heat resistance of that plastic is? I know the bumper is very close to the exhaust but the material properties I'm sure are different between the two plastics.