has anyone cut their rear bumper to make it higher and completed it with an angled diffuser?

 

I'm in the design phase for the rear diffuser. Nothing built yet, but it will be ready soon enough.

 

i bought thin sheet aluminum from a local metal supplier for $25. last time i was there the sheet they had was bigger and i paid $65 but i made a diffuser out of it too! those places always have scraps (portions of a 4x8 sheet) for cheap.

i can honestly say the difference, even on the highway, is night and day. my car will not budge 1 inch even in a serious crosswind (40mph +) driving 60mph and above. i bent up my old one (splitter) at vir last oct. and hadn't had it on for the last few months. and i just recently cutout a new one, and it's so stable and drives perfectly straight, it's amazing. i make zero steering corrections when driving at speed now.

here's a few pics: btw, i have it held on at 4 points, 2 stock on the ends and 2 i made from allthread and washers/nuts, with a couple L shaped brackets bolted to factory threaded holes in the bumper support. it comes off in under 3min. and was so strong it only bent the corner up when i went over the curbing in turn 2 at VIR! (4 wheel off)







this is a pic of the splitter with an air dam i made to lower the frt. end of the car for fast tracks.



here it is at the track with the airdam/splitter painted. also ran my diffuser and ebay carbon wing with custom alum. legs.





i think i'm gonna make some slightly larger end plates for the wing, also gonna open up the rear bumper to keep it from catching air. either holes or slots/grille material

 

couple more pics:





same idea on rear diffuser mounting. 4 points, 2 factory bolts (rear brace 17mm bolts) and 2 L brackets ( bolted to factory tow hook mounting bolts) with allthread and washers/nuts. the allthread makes it adjustable, although i always just put it flush with the bottom of the bumper since i read that too much angle will hurt instead of help. the way it is angles it about 5 degrees.

 

Moar pics of assend + info on diffuser plz.

 

it looks good. definitely not streetable around here though.

 

great work spoolin! i want the same thing for my car. i am looking for a sheet of aluminum now and will start to make one soon.

 

I second the aluminum...if supported properly. I've had mine up to +150mph (on the track) on the cobra and I wouldn't drive the car again w/o it. Miata is pretty much the same.

Dig around over at http://www.corner-carvers.com/forums/ for more aero tech....it's been discussed to death.

 

I need some aluminum welding equipment.

 

That's actually steel...I do have an aluminum mig gun though....I want a TIG though...maybe after Miata is done...

 

i'll take a few more pics since i have it off right now. i had the main piece bent to make the ends. the center dividers are bolted on with stainless bolts and nuts. (nylon locking)
i could have welded or riveted them on but i was afraid i might bang them up and have a hard time replacing them. i actually haven't bent the centers but the ends have been bent a few times before backing out of steep driveways. but it only takes a couple minutes to flatten them out and spray blk. again.

i am making some side pieces to finish sealing off under the rear bumper now that i have some extra material from my new splitter and i'll be cutting out the bumper to release trapped air.

here's a couple pics where you can see the forward mounting points. they are the 2 17mm bolts that hold the rear bracing on.

 

Bringing back an oldie but goodie....

Savington, any thoughts towards canards to aid in airflow over the spats? I shattered my air dam awhile back and am in the middle of a rebuild. I've added the spats to cover the front tires, and was considering the canards as a drag reduction device. Still not too sure what I think though.

--Alex

 

a canard creates downforce. if anything it might ADD drag. if your worried about the spats making drag, not sure canards would help you. are the spats at a 90deg. angle sticking straight out? best bet would have been to make them slope outward. think of the shape of the newer bug deflector's on truck's. only this would be vert. instead of horizontal. good luck.

 

I'm not worried about the spats increasing drag really. The way I understand it, they are a drag reducing component. Even though they are quite vertical, (they do curve with the fender well) it is the same frontal area as the open tire, yet less drag than the rotating tire.

What I was hoping, is that a canard may help the air "up and over" the spat. My understanding on canards is that they are not really downforce creating additions. (though they do create some DF, its not thier main purpose) They are designed more to swirl the air flow to prevent it from finding its way under the side skirts.

--Alex

 

Ok, I know we are talking about under body aero improvements here, but when the issue of having an open top came up it got me thinking, and I'm sure someone has already though of this, but has anyone attempted to make a hard top that tapers back like a z4 for example? I think it would have a significant affect on the under body aerodynamics over the standard hard top.

 

SEARCH BUTTON!!! AUTOKONEXION makes them....

 

Also, there is a guy in cr.net right now about to finish his fastback hardtop. He is claiming to sell them eventually for 1800. No idea how it will look, or fit.

Back to underbody aero plz...

 

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Sigh, sponsored show vehicles.

 

I have a sponsor, its my wallet.