Ryan, I kept up with your build on the other site, the underbody you are mounting was aluminum, is that correct?

Excellent. thanks for everyone's help.

Ok aluminium it is. ill get some X shaped creases put in it like air con ducting for rigidity.
what's a weld nut? do they mount flush? rivets make this whole job just- drill. rivet. bolt. very straight forward.


Lighyear are you suggesting to make an alloy plate that is wider than the body is?

thanks,
Dann

I think that he's suggesting something like this:

https://www.miataturbo.net/attachmen...ine=1356824868

You'll want to minimize the amount of air being sucked under the car from down off of the sides.

- Tom

I'm planning a V8 Supercar style side-skirts, flat panelled from suide to side, of course that brings thread back to jacking points ;)

What if you had some sort of easy access release for the underside bolts for SS and used low profile ramps to get to them. I'm not as experienced as you fellows, but that has just been my thoughts watching Ryan's build and thinking up my own aero pieces.

The diffuser I made is all aluminum. The first flat underbody I made was 1/8" ABS. It held for 250 miles round trip on the road and a full track day at ACS, but it has warped, so I am now making version 2 out of aluminum - no plastics that can warp from heat.

-Ryan

Dann, weld-nuts can be found here (they also sell good quality riv nuts):

McMaster-Carr

Riv nuts are not the same as regular rivets, not sure if you've looked them up, but they require a special tool (different than a rivet tool) and specific inserts for the particular size thread you're doing, and most of those tools are $50+, so if you have a welder at your disposal, weld nuts can save you money. Plus, like I said, weld nuts are more reliable.

-Ryan

I've used dezus fasteners on 2 cars, If you do them right, they're awesome go in easy, never come undone by accident. If you're sloppy, lazy on the install, or dont have the right length 1/4 turn part they suck because you can never get them in or they dont stay. I like to tape them for extra safety because we have had the main body have two of the 3 dezus that hold it on come un-done from cone strikes before on the car that was done sloppily.

fiberglass on splitters, I like giving them a light coat of the cheap polyester resin, but no glass mat, on all sides and edges to prevent it from absorbing water and warping. Its a bit tough though to get it on without making the spiltter heavy, wood likes to soak up the resin. I wonder if the resin will stick to primer.

As for lifting points when larger side skirts and flat under tray installed I would look to the rally world and use the pin stand method. Just build an adapter to sit in the pin socket to jack from. This will also allow a full width under tray.

^^^ I was going to suggest something similar. All you need is a hard point that penetrates through the undertray and transfers load to the rocker box jack points, or the frame rails. Hell a 1" dia thick wall steel pipe (hardware store) cut to length and stitch welded in place would do it.

I am talking about jacking straight-up from under the car. You will need a low profile jack for race ride heights. Pin jacks coming in from the sides (like a E36 BMW M3) or like mentioned above would do the trick as well. That will take more welding than what I described above.

Or go full baller and have built-in air jacks.

This thread continues to make me want to do things to my car that reduce its street driveability. Since such things can't really occur, I am conflicted. Attempting conflict resolution via beer ingestion.

Good plan on the beer. Works for me.

Drink the beer, then go back and make the irrational decisions.

Has anyone here attempted the pin jacks before? There's no way in hell I can get the front end in the air without taking half the nose off the car. I'd like to do it to my RX7, but can't visualize how to do them without having them protruding below the rockers.

How about welding FM jack adapter plates (or something similar you build yourself) in place on the car and build your undertray/skirt around them?

https://www.miataturbo.net/attachmen...ine=1356968478

Looks like it would work well except for those of us with these damned side skirts...

You just have to cut a slot either side of the pinch weld in whatever skirt you have there.

Dann

Im getting started on my project in the next couple of days, ill post updates.

Dann

Updates and pics - than they better not be upside down ;)

I'm cleaning the increased air pressure in the rear wheel wells. Still have to customize the rear bumper

https://www.miataturbo.net/attachmen...ine=1357007662

https://www.miataturbo.net/attachmen...ine=1357007662

https://www.miataturbo.net/attachmen...ine=1357007662

https://www.miataturbo.net/attachmen...ine=1357007662

https://www.miataturbo.net/attachmen...ine=1357007662

https://www.miataturbo.net/attachmen...ine=1357007662

https://www.miataturbo.net/attachmen...ine=1357007662

https://www.miataturbo.net/attachmen...ine=1357007662

Great idea, RJ. Did you do the same for the middle of the trunk?

no, I left the middle of the middle of the trunk were it is until i order a fuel cell

Very nice. I have the rear "flaps" cut out but I haven't cut the jack recess yet. Why not cut the flange and take that weight out?
No aerodynamic reason to. The jack recess is in the tire wake while the center of the trunk shouldn't be in the stream of air due to the diffuser.

Which part?? Happy New Year

The flange with 2 holes on the top of this picture:
https://www.miataturbo.net/attachmen...ine=1357007662

I'm just trying to make sure there isn't a function for it I missed. Happy New Year :party:

And the trunk's belly is a structural rigidity element that shouldn't be removed unless something else structural is added.

I don't know why I left the flange there, I guess just to add flair

True, I was thinking of linking the two rear roll bar mounts. Sorry to get off topic of Aero. Hey Six I will be in Tampa soon

The section 1993ka24det cut out is also a rust point. I cut mine out when I did the swap for that simple reason.

I've seen the trunk resessed area replaced with thin light material on race cars at TC Design Fab, Tony knows what he's doing over there, I'm guessing his cages take care of any rigidity issues. (They tie into the rear shock towers)

pointy is for airplanes that go past the speed of sound.. they NEED pointy to make the shockwave break where the designers want to.

below that speed, look more at cargo planes, with their curves for air funneling.

A ton of people have this misconception that sharp and ponty means "faster"

When F1 teams back in the day hired some Boeing aero engineer to help them, the engineer told them "you dont need me, you want the guys that built the WW2 planes, aero works different when you go past the speed of sound"


You put anything in the airflow that is moving air to the side or up or down, it will cause drag. The splitter is just sperating the air, and then directing up and over, or to the sides, creating high pressure on that side(s) (gross oversimplifaction I know)

now question i have, people that run with canards, depending on if you run a clockwise or counter clockwise track, can you test running one side or the other.. see if raising pressure on one side of the car could help? I know oval cars are set up on the extreme end for that kind of stuff

Yep. If you want low drag at sub-sonic speeds you should be thinking tear drop, not arrow.

https://www.miataturbo.net/attachmen...ine=1357858110

Good picture, but isn't the shape and the resultant cd more to do with the back of the object and the air seperation /turbulance?

I mean what if the first pointy example was pointy at the back too? Not a dome as shown....I suspect then it would have a pretty good CD again...

Hence why F1 and all high end race car designers focus so heavily on the rear end.

As do the yacht hull and keel designers, wing keels were designed to minimise drag not provide lift and so on....Boeing with the vertical wing tip extensions...

Which leads me back to the MX5....undertrays and diffusers etc....It would be great to know how much of an effect they could potentially have on our little cars.

Then we could decide on whether it is cost effective to focus on that area or not...I mean if "theoretically" the best diffuser gained 1 MPH and 1 KG of downforce I can see many other areas to focus on...

If on the other hand it was theoretical to see a gain of 15MPH and/or 40Kg downforce, it might be higher up the priority list.....

Some experienced designers must be able to give us a ball park.....

Lets keep this thread on topic and avoid the engineering student discussion on who's brain is bigger to another forum. This is more of a rocket city rednecks aero thread.

Very Nice! Is that a one-off or a production piece?

If you are referring to the white NB in Jake's post, no. OTS from Autokonexion. Something I designed but never had built for myself. Mike liked it and put into production. Good race or street nose, covers 9's, low drag, room for brake ducts and oil cooler without hacking more holes in the nose. In the end we went with the ABS sheet set up instead.

Exactly what I was thinking. Nice job! Now only if it were for an NA ;)

...and fit to stock fenders instead of flares.

They make a fairly similar NA bumper as well

https://www.miataturbo.net/attachmen...ine=1357964222

^ definitely not as good aerodynamically.

For you V8/LS1 guys, how big are your radiator openings in your air dam? Mine is measuring 6" tall by exactly the width of the radiator core including end takes, but I can't help but feel that I'll be choking off the radiator somehow, and am terrified of having overheating issues. I'm using an ABS inlet box with a venturi shape that seals to the radiator which is laid forward at an angle (with a mother thumper SPAL puller fan on the engine side), so all air would have to be drawn in through the inlet box.

https://www.miataturbo.net/attachmen...ine=1358026779

Sounds about right. A rule of thumb is that you want the inlet to be 33% the area of the heat exchanger.

Sweet, thanks. I went from a stock front bumper to this, and it's just disconcerting seeing something so "small" in comparison to the much broader looking front end, even though I know it should be fine.

Indeed. I went back a little ways and cleaned up the thread. Keep it on topic please. Feel free to report the off topic crap when you see it, one of us will clean it up. Carry on fellas.

+1 on the small inlet size. It does not take as much as you think. Mine is no larger than stock despite the LS1.

What are you using on the splitter to mount the airdam? I looked all over Lowes and couldn't find anything like it.

Aluminum angle would work fine.

How many are you using? and you need to update your signature pic, Its not up to date lol

I think the supply of COT wings are getting low

I did things very similar to many on this thread. Here is the splitter and air dam rough cut:

https://www.miataturbo.net/attachmen...ine=1366273234

I ran a few pieces of 1/2" x 5/16th aluminum bar stock behind the bumper right behind the belt line indent and banged it into the shape of the bumper nose. I secured them through the front with countersunk 1/4-20 machine screws. Once this structure was behind the bumper skin, I was able to drill and tap through the air dam to mount it on the nose and have enough structure that I can take the air dam off as needed.

The air dam is attached to the splitter with 1" aluminum angle (1/4" stock) cut into 1" squares. These are also drilled and tapped with the same 1/4 - 20 stainless button head screws as the top of the air dam is mounted with.

I ducted the heat exchangers in such a way as the splitter, air dam and bumper cover can be removed easily without disturbing the ducting. The leading edge of the box is just taped on 4 sides but otherwise share no structure with the aero work.

https://www.miataturbo.net/attachmen...ine=1366273234

There are 3 sections to the ducting so each area gets a portion of the clean air. The lower most part is the oil cooler and brake ducts. The middle section goes directly to the intercooler (sealed 360*). The upper scoop goes directly to the radiator. The 'exhaust' of the intercooler runs into the radiator but the whole things seems pretty effective.

https://www.miataturbo.net/attachmen...ine=1366273234

I chopped up the OEM hood with a mini scoop and some aluminum louvers to extract extra air. The performance on track when combined with the COT wing dropped 6.5 seconds off my best time from last year on a ~2 minute track. I also got a new tune which added some WHP but overall the aero was a HUGE gain. The setup is pretty balanced but I'm looking forward to more seat time to really see how things shape up. :party:

Head to the garden center. It's a type of edging that is used to hold garden/pathway stones in place. It will be near the coiled stuff, but comes in 6 foot lengths.

Nothing at my Lowes like it

mr_hyde--not enough pics, need more

Not sure if Lowes does, but Home Depot does. Here it is:

Valley View Industries Diamond-Lok 2-1/2 in. x 6 ft. Plastic Paver Edging-DLLF6-50 at The Home Depot

Here's a good explanation for why you don't want to connect your air dam to your splitter ;)

https://www.miataturbo.net/attachmen...ine=1366304103

Moti

Is that the consensus? I have been thinking it would be prudent to design more 'breakaway' characteristics into the design. Currently, the air dam provides some vertical support to the splitter.

I would avoid connecting them, the way you describe it sounds like one will need to give in case your splitter contacted the surface like my pic above.

Moti

I have my dam connected to the radiator inlet duct with 4 dzus fasteners, but no dzus fasteners to the lip on the splitter. I didn't see any advantage to doing so, the ABS is stiff enough that it can't get pushed back at all.

In regards to the breakaway characteristics, I run a COT splitter, not a full undertray right now, and used a combination of cable mounts with some stitch welded 4130 stanchions. If I ever really hit the sucker hard, the cable mounts will probably keep it from flying under the car, but the stanchions will shear without doing any major front end damage. Using the front cable mounts also allows the splitter to flex upwards a little bit if it gets hung up on a trailer ramp, etc.

I'm not worried about contact like in your picture. I'm worried about hitting the sand and having the nose of the car act like a giant snow shovel. I will give some more attention to the design characteristics needed to allow a clean breakaway.

I've heard of people using nylon hardware to mount splitters. Sized appropriately, nylon bolts would shear well before any real damage is done.

Never thought about that but that's a really good idea. It wouldn't be hard to figure out with some tensile/shear data.

Random google search found this: Plastic Nuts & Bolts.com I'd like to find something more official but it's a good start.

Ive got my splitter mounted to my air dam, but the 1/4" abs is plenty flexible to allow the air dam to "crunch up" in a situation like BlackBird's. I had to have it loaded on a flatbed after an off-track excursion and it collapsed surprisingly far (it seemed like over a foot at the time, but who knows) without any permanent damage.

But the fear of shoveling is a whole other matter... that could be a problem, and some sort of breakaway is probably the best solution.

The problem with having the splitter break away is that in too many occasions it breaks away at the wrong moment and the results can be quite dramatic.
A few months ago a car lost a splitter on track @ WSIR, causing it to go off track and wreck real bad, both driver and passenger were injured.

I fear that the potential for a momentary loss of steering can result in a major crash, and have no intention checking how it feels while going 130 around the banking @ ACS or T8 @ WSIR...

Moti

Dollars spent: $175
Hours spent: 10
How effective: 3 so much so I have insane oversteer
0=slower, 1, no improvement, 2 =slightly better,3= big improvement
Materials used: Harwood Dzus Fastners, Alupanel, 1" square tubing from Lowes Racing
Bracket location: Mounted to bumper mounts
Tracks tested on: Not Yet
Race/TT class built for:

https://www.miataturbo.net/attachmen...ine=1366605131

https://www.miataturbo.net/attachmen...ine=1366605131

https://www.miataturbo.net/attachmen...ine=1366605131

A pic of the under body, I making a NACA duct for cooling as I type (talented)

https://www.miataturbo.net/attachmen...ine=1366605131