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Making a Custom Rear Diffuser

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Kai Hefner

Freelancer
480
272
Jun 21, 2018
Calgary, AB_Canada
I bought a 2g dsm, some stuff needs some work and especially the rear bumper. The sides of the rear bumper are 2 inches off the ground and scrape everywhere I go (I don't live in California with all your flat roads).
I took off that bumper, bought a stock 2g bumper and I'm thinking of throwing on some diffusers and some metal to make it more aerodynamic (less like a parachute).
I'm also so YouTube stuff occasionally.
Would anyone benefit from me making a video on how to transform a 2g bumper into less of a parachute and with some sweet rear diffusers?
 
Yeah, that would be nice to see.. not many people make how-to videos on these cars anymore.. so yeah, i would appreciate if you documented your process of making a diffuser, i want to make one myself :thumb:
 
This is a good idea, I've always liked rear diffusers.

Looking forward to the video.
 
If you dont trim your bumper it has to be fully enclosed which is alot more work but if you dont then its still collecting air,
 
The big air pockets are on both sides of the spare tire framing right? I was thinking I could just create better airflow by adding on some slanted pieces on the bottom of the bumper, that slant at say, a 45 degree angle into that big air space. So air coming from the front of the car, will be deflected downwards out of the inside of the bumper.
 
I was working at it last night. For aerodynamics and weight, I've determined that the job will involve cutting up the rear bumper. I'll go through all the measurements/failures in the video so that you guys can have confidence in recreating it if you want.
 
So I did end up making the diffusers but ran into a lot of shortcomings that I didn't really end up recording the entire process. Plus I was not happy with the outcome and I'm planning to remake them once I get home (I'm away at school).
For a really brief rundown:
I cut out big holes on each side of the bumper, because they essentially acted like parachutes for air that was coming under the car. It may be placebo affect but I did feel a difference in how hard the rear end dragged at high speeds. (IMG_6082)
Then I decided for some weird reason to use acrylic for the diffusers, which was the worst idea ever. I should have used lexan or aluminum or steel. The aryclic held up to 120kph highway speeds but some kid at a car show running around my car and hitting a diffuser, would snap it off, or my buddy just trying to walk around my car and bumping into one would snap it.
Franky this was one of my first custom jobs and I was proud of the creativity and such but not proud of the outcome. The diffusers looked incredibly ricey and were just a burden to deal with. (IMG_6050) (And yes, my bumper is a different black than the rest of my car, that's because I got this bumper off a junkyard car for $40)
The middle diffusers didn't go under the car enough to really do anything, and the top mounting part for the diffuser stuck out of the side of the car, frankly ruining the nice body-lines. (IMG_6049 (1))
When I was back home, I began remaking the diffusers out of steel, and a lot less ricey (hopefully). The middle diffusers will be more functional, actually coming under the car, and much closer to the ground. The sides will be more flush, everything will be the same height, and jut out the same amount, not as aggressively as before.
If there is still interest I can record my progress/measurements of my remake. I didn't want to post about my previous ones because I wasn't happy with them.
 

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