Full Flat Undertray DIY
 

Recently.... I finished an full flat undertray DIY.
to maximize performance of RE-amemiya rear diffuser, it was designed to completely cover bottom of tranny and exhaust lines.
panels were made of aluminum 2.0mm sheet and placed a few NACA duct for cooling.
the yellow front undertray were self-made years ago for c-west aero.
see below pictures. ^^

https://cimg9.ibsrv.net/gimg/www.rx7...165e954c15.jpg

https://cimg0.ibsrv.net/gimg/www.rx7...43d414cbf8.jpg

Nice work

Yes, very nice. Slotted holes and clean fit.
Was the factory tunnel bracing or anything else removed? What were the panels secured to? What hardware was used? Any noise/rattling?

Really nice work.
Does it feel any different on the road?

Bet you could make a killing selling those. You already have the hard part done. Now mass produce.

Very nice! That would be a REAL chore to make without a lift!

I've thought about doing something similar, great job there!

Dale

Now that's a flat bottom!

Damn, that's impressive. I like the NACA shift to cool the exhaust.

Vince

Wow, hadn't realized there was room for that deep of a venturi under the differential- that might do something at speed!

https://cimg0.ibsrv.net/gimg/www.rx7...c9b5d867f4.jpg
I made the brackets to hold the panel. and can't hear any noise.

Love this. Well done.

WOW! This is awesome!

:worship:

This looks amazing! Great work :)
You could probably even sell these.

...or better yet for you, mass produce templates and bracket instructions and sell those. No fuss or hassle of having to produce, package and deal with shipping or customers :)

I would be in for that!

Jpr

Whoa! Thats perfect! What about the undertray braces. Did you have to remove them
?

​​​​​​
+1 on this!

yep. the stock under-braces fully remains.

for online selling, I'm preparing packing and installation instructions.
maybe It will be available in Feb.
thanks~

Yes! Please please make this happen. This will imensly help the fd

might be some variance with how the dp.. wastegate dump and exhaust hangs past these panels... but yeah nice work

That looks really clean! Well done, Jin-74!

Personally I think this is exactly why I would prefer to purchase a template over a finished product .I'd rather modify a template and make the part fit my car exactly, vs modifying a finished part and it not looking/working perfectly.

Problem is that selling a template like that put a lot of faith in the community, as you are basically selling a very easily stealable product (paper).
Just take one guy to put it up at ebay for half the price to ruin the business for the original guy.

Tho, i would buy a template myself for the same reasons you mention. :D

nice. Count me in for a set ! :)

I would prefer to buy a "finished" product over a template. Maybe with the exhaust/downpipe portion undertrimmed so that the specific trim could be done on a per-car basis

Hell, I'd rather have a step file or a scaled 2d model. Sell the model and let people get it laser cut on their own. You make money selling the model, don't have to hassle with shipping, community gets product. Win all the way around :)

Whether you sell the template or real thing, though, it doesn't matter. This design is fairly simple to copy.

The challenge with this as a 'bolt on' product is the downpipe and exhaust routing. Soooo many variations, there's no way to make a 'one size fits all' solution.

IMO - you sell those pieces uncut and let the end user cut to fit for their specific application...


Looking forward to seeing how this progresses!

Dude, this is rad as shit.

+1 on that. Problem with a template is all the cutting and bending

And completely uncessary for street applications :hahaha:

But, that's never stopped us before ;)

Exactly. A proper laser / waterjet shop with a press brake could crank out 100 of these in a day.

Most DIYs guys could probably muddle through - but 'results may vary' as they say.

I'd want to use a template as a baseline, then custom cut openings to fit my car exactly. Once that's finished, then powdercoating and totally unnecessary custom bling-bling fasteners of course to finish it off ;). This would undoubtedly stablilize the car better at 180mph+ (LOL).

All it takes is an arts and crafts store, some straight edges and an exacto to do the same to these parts once they're released. This has happened to a few porting providers on the old eBay already. I'd rather have faith in humanity, as well as support manufacturers than to jump directly to assuming the worst of people :)

Do the templates in CAD without exhaust cuts.
Sell the files (.DXF) encoded so it can't be duplicated. IT guys, can this be done?
Buyers start your own local group buy. Contract with a local water jet/laser cutter that does press brake work and buy several units at a time to get cost down.
You would have to cut your own exhaust reliefs after the template are cut.
180 MPH smoothness.

1. Esser
2.

For what it's worth, I'm very interested in purchasing. With most things, I'm ok with custom fitting stuff as that's not the hard part. The hard part is taking initiative to even come up with the design and have it come to fruition, so thank you for that. I look forward to seeing what comes of this project.

Would be good to see even a rudimentary flow analysis (or a qualified opinion) for an aero product.
*I have doubts about the interface with the REA diffuser
*Those NACA cutouts need actual NACA ducts to be effective
*The gils under the transmission look like they're angled wrong
*Does not casually resemble actual flat bottom race cars you can google

But, leave it up to this community to get all giddy over something with zero r&d and zero results.

so you mean it does not resemble anything like this?:
http://forums.rennlist.com/upload/f355aero.jpg
Please feel free to wait for someone to do a CFD analysis for this design, meanwhile ill take your spot in line........

Jpr

I can make them here in nj if you want to work out a deal at least for the US based customers

Yes, that's exactly what I mean. But, I guess if you have zero appreciation of aerodynamics or engineering, then it all kinda looks the same.

https://cimg0.ibsrv.net/gimg/www.rx7...bbf01ffea6.jpg

I wasn't in line, but please help yourself to the completely speculative benefits of armchair engineering. All the kids at hot import nights will probably give you mad props.

This is why I love the FD community. Plenty of people with great fresh ideas plus a few experienced folks injecting a healthy dose of skepticism and critiques.

I think the concept is sound. Execution will def take some trial and error. Bolting it on seems easy enough and I am sure most of us have a track near by to do some real world testing. Looking forward to see how this project progresses!

Agreed/interested
 

I agree it's a great idea and nice to see someone going in this type of direction. If you are serious about this I agree that some r&d needs to be done to see how effective it is. The fd is a real sports car not just some ricer car that we just add things on it because it looks cool or impresses some car posers. Either way if it does improve what the Japanese have given us them I am in.

Well, you need to make a few to actually get that testing. Make me a set, and I'll test them at VIR, Watkins Glen, and Summit Point, and I've got lots of data and video of straight speeds with which to compare it.

I didn't get any advance CFD data on my lip spacer, but I can tell you it works like a champ.

Yep
 

Sounds like the way to go to me. Best testing is in real conditions (track)

I guess that a mechanical engineering degree and 30 years as a consulting mechanical engineer are all for naught............

Jpr

A flat bottom is a flat bottom.

If it is relatively smooth it will decrease the boundry layer and allow the air trapped under the car to exit faster.

Whether the venturi/ diffuser actually has even more effect and creates a localized low pressure area is a more complex subject, but easily verified with a length of clear tube with some water in it.

There is a gap between the leading edge of the flat bottom and the unibody which would allow air to enter, and it does not appear to make any attempt to evacuate that air in an advantageous way, as opposed to the example Ferrari (which doesn't have gaps, or vents, or NACA's). Moving air from top to bottom in any fashion creates lift. It's imperative to avoid any air from moving over the top of the flat bottom. The Ferrari example also dispenses wheel arch air to the sides with an angled attack profile. Please also note that professional flat bottoms don't have exhaust cut outs, but instead form around the exhaust. And, NACA ducts rely on vortices and laminar airflow, so you can't just cut out a NACA silhouette and expect it to move air except like any other fancy hole with a pressure differential.

This project has a lot of potential, and is an impressive effort. But, don't mistake that for real engineering and efficacy. The current design is suspect, at best.