What are you looking for in a diffuser?
 

We've created an agressive diffuser with a 6" flat bottom for the NA and NB. It accomodates exhausts that exit the standard position and to the side, both rear tow hooks, and requires no drilling. It's CNC laser cut, powder coated, and easy to install. We also offer free shipping. We're looking to get some input from the Miata community! What do you think?

https://cimg7.ibsrv.net/gimg/www.mia...453fbc5437.jpgNA Miata racing diffuser with 6" flat bottom
https://cimg1.ibsrv.net/gimg/www.mia...a04a809015.jpgNB Miata diffuser V3

For swag points, it looks OK( if for some reason you're into that), and the fact that's PnP is gonna help. For function, I am not convinced at all.

Is this just a " we think it does this or that" or do you have any data regarding its effectiveness, CFD, real world test(tufts), maybe even ride height monitoring? CFD on a non-flat bottom miata would be cool.

I would like something that doesn't work with a stock un-modified rear bumper. Because if it does, then it probably doesn't work and is just pure stanceboi drift stuff for cool looks. Which is fine, but not what i would want.


2000 SEs are cool, though. So you've got that going for you. The overall construction looks much better than the R Theory diffuser i bought (which is also stanceboi drift stuff for cool looks), so that's good, too. Make it functional and i'm interested.

I'd still by the warhose modular before this. I would not want my diffuser mounted to the subframe brace locations. R theory has a nice bracket Idea to eliminate that.

why? its a 12mm dia. bolt. I dont see much problem with using that at all. a bolt on mount would likely add a moment arm.

R Theory diffuser is mounted to the subframe brace locations. Source: I have one on my car.

Because I would mount it in a different fashion rather than to that 12mm bolt. It doesn't need it. I don't like sandwhiching the aluminum panel there when that bolt should be really tight. Those weld nuts break easily if over torqued which could happen due to the aluminum panel. Can't use PPF brace :] I guess if you remove the brace, then it wouldn't have a bump leading into the flat section..

All of these concerns apply to the R Theory diffuser, which imo has much inferior overall construction to what is shown in the OP.

Also: Those weld nuts often break when taking them off for the first time you drop the diff in these cars. I break them on purpose and replace with good quality SS nut/bolts.

If you think that small bump makes any difference after flowing past all that other junk up front, i think you are wrong. not sure of the alloy used but, sandwiching 6061 or 5052 is fine. wont hurt it.

I can't find any pictures showing Rtheory mounting. I only ever saw a small 90* bracket which bolts to an existing 8mm bare hole on the subrame(where the 949 brace bolts to). Then gives a horizontal surface to bolt the diffuser plane to. Sure bolting to the subrame brace is easy and stout. It's not a deal breaker. Did you lok at the other miata diffusers on the website? They don't look like they are going to work well. Especially not have a nice smooth leading surface up to the diffuser.

What pictures would you like? I can go out to the garage and take pictures of how it is currently mounted to my car using the subframe brace bolts that you don't like. I can also assure you that the R Theory diffuser will not work well. It's not big enough, not wide enough, and has an un-functional amount of air gaps between the parts that are weakly riveted together.

That's why there should be a flat belly of some sort. BUt on this diffuser, that initial bump from the brace itself is going to affect the fuction. It only has a very short section of flat after it and then woosh up to the diffuser immediately.

Here's a pic that shows everything that you're complaining about here. :P

https://farm5.staticflickr.com/4451/...f0f17ed3_b.jpg
20171016_171011 by concealer404, on Flickr

No need to.I wasn't aware the R theory mounted to the subframe in the same way. I'm not looking to buy an R theory or was I claiming it was designed better, differently, other then the bracket I mentioned. Both products look pretty similar, another option is great, if it was intended for cut bumpers.

Cool. :)

The R Theory brackets are for the rear-most attachments. They're fiddly, cheesy, and not something i'd call a "plus."

The more i look at the OP, the more i think i could work with that a lot better than what i've got, but it would have to be higher in the back/exit, first.

Discussing, not complaining! For all the hard work and price, I would just expect it to be executed a little better than what is already out there.

Oh!

Boy i feel dumb. I didn't even catch that this was actually currently for sale. I thought this was a gathering interest/how can we improve it kind of thing.

Well technically they are asking for input on what the kitties have to say.

Ok well... this kitty says it looks well-constructed, but needs some tweaking to be anything but hardparking poop.

BTW, even with a full length flat floor, I would still doubt if it could offer any sort of measurable advantage at that height, without sealing off the sides. Maybe less drag, but that would be mostly due to the (non-existent here) flat floor. Single step-change in inclination and no attempt to move the (numerous) bolts out of the flow (at least by using cap head ones) points to looks over function. At least, there are no (visible) gaps.

Thank you for the several comments! We were definitely asking for input as there is always room to improve. We want to hear from you.

The V1 and V2 diffusers for the NB were our very,very early attempt at diffusers and were not very popular. The V3 model as shown in the pictures on our thread post represent our most recent production. The V3 does attach to the rear subframe bolts. Attaching our diffuser at this location is sound as we have had no problems at Buttonwillow Raceway. We do in fact use 0.08" (12 gauge in alum.) 5052 aluminum which is very strong/stout.

The V3 is close, if you would pretty much make it again, but this time not taking the bumper cover into consideration at all, i would be interested. A diffuser that does something should require at the least, a substantial bumper cut.

Make V4 like this, please.

https://cimg3.ibsrv.net/gimg/www.mia...fb898ced45.jpg

YES.

10/10 would buy.

https://cimg8.ibsrv.net/gimg/www.mia...35059e4a94.jpg
I would vote towards a diffuser like the black AWR NA diffuser, but wider.https://cimg2.ibsrv.net/gimg/www.mia...2292fe3cc3.jpg

Aren't these last few examples openings too big to create the necessary venturi effect?

I'm pretty sure diffusers are moot if not paired with a flat bottom on our cars, correct me if I'm wrong on that. Also what's the angle like on it, it looks fairly steep in the second picture, too steep and it's just going to seperate. Seeing no real world testing leads me to believe it's not really going to do anything.

I agree with you on both those statements. If i remember right the sweet spot on diffuser angle is around 7°

Could you get a higher angle with vortex generators? Isn't the whole angle limitation to prevent flow separation?

7deg is a very rough guideline; depends on a number of factors really, but yeah the main point is to avoid separation. As said, the step transition is not helping. Main issue though, lack of the structure on front of it (flat floor or otherwise) and NO sealing from the sides.

A sharp angle does in fact lead to flow separation, as does a steep angle. Sealing the sides of the flat portion can definitely be done; it would just bring the diffuser closer to the ground. We plan on doing track testing on this diffuser but it also sounds like we need take into consideration a few more factors while disregarding a few of our initial considerations. From a flow perspective (race perspective) this is what sounds like needs to be done:

• Use a long curved surface (as opposed to a single-step) that outlets at an angle that minimizes drag but maximizes down force. Cutting the bumper may or may not be necessary as an angle too large will create flow separation.
• Minimize the number of flow impediments (the bolt heads).
• Make sure the diffuser extends from tire to tire - air flow under the entirety of the car needs to be captured.
• Seal off the sides of the diffuser from beginning to end to avoid leakage (kind of like something Lotus did back in the day when they decided to drag "skirts" on either side of the car).
• Ignore where standard exhausts lie and do what is most effective - exhausts can be built around the diffuser.

We truly do appreciate the input!

Have you checked out how the guys at Verus Engineering are building their parts?

They even include basic CFD numbers as well.

:inout:

Their work is beautiful. I will be looking into it. Thank you!

Have you considered making a flat bottom for the Miata? Something made out of aluminum with attachment hardware and goes from the front subframe back to the rear brace where your diffuser starts and in semi-modular sections so it's easy to ship / swap out replacement parts. I don't think there's anyone that makes anything readily available like that tbh.

Ive seen some CFD that shows they are effective even without a flat floor. The flat floor helps a lot, but considering how little a diffuser weighs it still make sense to work one into the car even if you cant legally have a flat floor between wheel center-lines.

This would be neat. Would need to make allowances for exhaust heat and diff/trans cooling.