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2g rear diffuser

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ebailey95

Proven Member
130
4
Oct 17, 2012
Portland, Oregon
Howdy all. Just wanted to share a custom rear diffuser rvaughn and I came up with. We've been itching to execute this project for a few months now and I recently got the welder needed to do the work so I fabbed a few up as soon as I could and I couldn't be happier with how it turned out.

Some info:
The entire piece is made from 10 gauge aluminum sheet metal which equates to 1/8in. The diffuser covers the entire bottom of the rear bumper all the way back to the forward side of the spare tire tub. There are 12 mounting points using 3/8 by 1in bolts along the bumper outline using factory hole locations as well as 3 mounting points in the spare tire well making the piece very rigid and solid to the car. The entire idea behind the project was to create a part that would be cosmetically apesling while stiffening up the rear bumper from flapping around at higher speeds, which mine did terribly. The end result accomplished both.

Fabrication wise, I made the diffuser with only three tools: a jig saw, and angle grinder with flap wheel, and my new welder. I'm a simple man :p

There are 11 individual pieces the make up the part and each are welded using 4043 filler rod, 100% Ar pulsed at about 125 amps. I'm using a Miller Syncrowave 210 on 110v (amazing machine). There are 6 vertical strakes spaced through out.

I'm happy with the end product. It solidified the rear bumper eliminating the parachute effect it had while at higher speeds and it looks good doing it :D I've tested it at 120+ mph and haven't taken it easy driving around. Zero clearance issues and no complaints so far beside the fact that it has a gnarly bite if your ankles get too close to the pointed strakes LOL.

Always welcome to constructive criticism and some honest opinions and/or recommendations.
 

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6.5 lbs, it is almost flush with the wheel well body in the front portion and is sealed to the rear due to the mounting points, strakes can be made to any height, we did four inches as a first test.
 
Last edited:
If wanted to do away with mudflaps could a filler be used to get a complete seal, and are you getting a complete seal at the front?
It looks nice and clean congratulations.
 
Finally somebody does this. I have been waitng to see what one would look like and without a doubt not dissapointed! Looks so clean. Great job!
 
We are only looking for constructive criticism at this point, if these go into production we will purchase the freelancer status immediately.
 
Is there a way to mount it without having to have the bolts/nuts sticking out the bottom? Probably won't make that much of a difference aerodynamically, just looks a bit off.
Maybe weld in some tubes where bolts need to be and drill for a counter sunk bolts.
 
I had been thinking of something like this because I didn't want to cut holes in the rear bumper so it doesn't act like a parachute. My welder only welds steel so steel sheet metal isn't what I would want. My other option would be wood since I have tools for that. What do you think? A nice walnut stain? ROFL

Nice work! Watching for updates and a new freelancer along with something to put on my want list.
Like to see pics of it on a lift from underneath.

Oh and another question are the mounting points in the spare tire hole at the rubber drain plugs? If not that could be a nice improvement so there is no drilling holes. I think my talon bumper sets up higher than the eclipse so the spare hump might be in the way.
 
We have not had any real track testing, probably not going to get much more than some 1320 passes. We did try to design this thing with the intent of eliminating the possibility of the parachute effect and I think we succeeded but track times will tell more I think.

As for mounting, we did use all existing holes for mounting, no drilling necessary. The weld in tubes is definitely an idea although it adds some weight and doesn't make this as friendly if we turn it into a product for everyone. We will work on getting some better pictures of the underside of the car for you guys and you can point out to us how we can improve it in your eyes. As for the countersunk bolts, we are considering some options now, we just aren't sure on how to execute, we will look at this heavily with the revised design.

Right now the biggest issue besides recorded times is cost, this thing isn't cheap. If it is found to be a truly 'functional' piece, I suspect we will gain more interest but for the time being the people we have marketed to locally/other media have flaked due to cost.

PLEASE keep the thoughts pouring in guys! We both hope that we might be able to eventually get our name on the freelancer list and need help making it happen!
 
Just to clarify, by 'tubes' i meant basically thick washers on the upper side of the plate so a countersink will have extra metal thickness to hold on to. In other words something like this http://i01.i.aliimg.com/photo/v0/381705023/countersunk_head_bolt_with_washer.jpg welded in so when the bolt is tight it sits flush with the bottom surface.
However, adding 'tubes' (framework) made of aluminum to support the plate could be an option if someone wants to remove the spare tire holder to save some weight.
As for saving some $ during production, could the plate be bent to form the exhaust tunnel instead of it being welded, or is it too thick? If it can be bent that will save some cutting and welding time, and some welding supplies.
 
I see what you mean 91-GS, the counter sinking would be a good way to go, we will take a look and see what we come up with, thank you for the suggestion. As for bending vs welding, at this point we are doing this in a garage with limited tools so welding kinda takes the cake since its available.

Keep the thoughts coming!
 
What are the odds of making them for 2GB Talons as well? I like the idea and where as my Talons bumper doesn't look to be quite as much of a parachute as the bubble butt the Eclipse bumper has I'd still like to see the possibilities.
 
Just wanted to update the thread. I have since added a lip up at the from to prevent air from slipping above the diffuser. The piece has been on my car for Almost 3 months and still going strong. It's doing its job and doig it well. I'm not afraid to drive my car, and i do. Here are some recent pics.
 

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