Ryan,

If you want to keep the lotus diffuser, I suggest you use some of that aluminum to fence in the rear wheel (this will keep the turbulent air from spilling into the diffuser.)

-Henry

 

Thanks Henry, definitely a good idea. I'm thinking about adding vertical fins to the diffuser running the whole length of it - I could do one on each side that is at the width of the inside of the rear wheel well that would hopefully keep air from the wheel well that spills under the car traveling backwards and not getting to the center of the diffuser..

-Ryan

 

Just came in from the second day in a row that I spent 12 hours in the garage. My roommates think I live out there. Maybe it's strange that this is what I enjoy doing most on my days off from work? haha

I've got about 5 projects all in various states of progress right now, and my driveway is literally covered with aluminum and ABS shavings lol. I'm really excited about the stuff that I'm making right now.

-Ryan

 

In from the garage. New sideskirts are 99.9% done - all I need is a zip tie, but I ran out. Seriously. Haha

Rear spoiler changes are done. It's now adjustable; 15, 25, and 35 degrees. (old was always 35*)

Mid-body underbody is done. Stretches the whole length of the car from front subframe to rear.

I'm 40% or so along on the rear diffuser. I'm making a center section from scratch, cutting the Lotus diffuser in half and using the outer sections of it grafted to the new center section. The new center is cut out, but I can't bend a 3 ft. long section of 0.050" 5052 aluminum by hand accurately enough so I'm going to find a metal shop tomorrow that has a machine that can do it. Then I cut the Lotus diffuser and get all mad scientist on it muahaha

Additional hood venting is 50% along - hood is cut, aluminum side plates are cut out, just need to bend and rivet.

-Ryan

 

Sounds like some serious progress is being made, I'll limp my 3 brake Miata over tomorrow and check it out.

 

^cocktease. hurry up and post pics!

same thing here, i work on car and think of ways to improve them as my relaxation.

 

pics Ryan!

 

Ok, all I've got is cell phone pics that I've snapped as I go so far.

Rear Spoiler

Goals were to make lighter struts, and make the spoiler easily adjustable so that I can switch it between track sessions.

The old struts had female threaded heim joint ends, and steel threaded rod the whole length between the two ends, with copper tube sheathed over it for aesthetics. Much heavier than necessary. Want to save weight wherever possible, regardless of how little!

The outer struts are now replaced with an endplate/mount . Here is the outline of these mounts traced onto the alumalite (made the template from cardboard):

With them cut out, I test-fit them with the spoiler at its normal angle (35 degrees from horizontal):

Then, I set the spoiler at 25 degrees and 15 degrees and drilled holes for those two settings as well (spoiler is mounted on hinges on the front edge). Then paint, and added a bracket riveted to the rear quarter panel to mount the front edge of the mount to. Now I just undo the allen on each side and tilt the spoiler to whichever angle I want and put the screws in:

Backside (these pics are at 35*):

The main goal with the outer mounts was to achieve the adjustability without adding weight over the old setup. Mission accomplished:

With the center struts, I focused on shaving weight. I got aluminum tube with a decent wall thickness and then ran a tap down into it (not fun by hand) to create threaded tubing:

So now aluminum tubing replaced all the steel threaded rod and the plethora of nuts and washers that used to be necessary. Weight difference:

All put together:

The aluminum rod on the center struts is threaded deep enough that by just threading the heads in more they can go from the length necessary for the 35* angle down to the length for the 25* angle. For the 15* angle, the outer mounts are so stiff that the center struts are not even necessary, so that's another 160grams less for that setting.

more to come..

-Ryan

 

Sideskirts

So obviously, the old sideskirts are off because they don't work with the new fender design.

The problem with that is the factory side-profile curves inwards a lot at the bottom and allows air traveling down the side of the car to spill under the car. We want less turbulent air under the car.

The old sideskirts did a decent enough job of keeping air from going under the car, but I've had this new design in my head for years now that should work even better, waiting for an excuse to toss the old sideskirts and do it right.

If some weight can be saved as well, awesome, old sideskirts were thin fiberglass so were already light @ 4lbs per side.

Step 1 was to make a solid way to mount the new ones to a part of the car that has very little provision for mounting stuff. I used weld-nuts. I posted a pic of these when I brought them home on the last page, but I'll include it here. Hardware of choice is Stainless steel buttonhead allen bolts:

Weld-nuts going in:

I didn't snap any pics of the creation of the skirts themselves. They are 6mm alumalite, 5' long, ~6.5" wide, and butt up against the pinch welds under the car. They sit 1/4" higher than the low point of the pinch welds so I haven't lost my jack location at all:

They fit nice and snug against the underside of the rocker panel.

The other feature I wanted was to deflect air coming down the side of the car from hitting the front of the rear tire. Plus, my fender flares were notched for the old sideskirts so it just wouldn't look complete to leave them.

Made myself a template:

Transferred that to 1/8" ABS:

Notched it to fit into the edge of the front flare, made an aluminum L bracket riveted to the sideskirt to mount the spat to and voila:

It'll be nice to take some pics of these once the car is on wheels and at ride height, but alas that will have to wait.

Total weight: 2.5 lbs per side

Weight saved: 1.5 lbs per side

-Ryan

 

I stocked up for all the projects:

 

I love what you did with the front fender. The rear air deflector looks tidy integrated into your flare as well.

 

Flat Mid-body Undertray

I'm determined that if I'm taking all the points for aero in Miata Challenge that I'm going to make darn sure that I've got aero that's making a difference. For a diffuser to work right, you need a flat underbody.

1/8" ABS sheet has arrived!

Spent quite a long time measuring and deciding on a basic shape. Here is the shape laid on on the ABS:

To mount it to the car in the front, I used the two rearmost front subframe mounting points with new longer stainless bolts.
I also made a tongue that sticks off the undertray - this tongue rests on top of the front subframe cross brace, so that the front edge of the tray can't get pulled down by air - it stays snug up against the underside of the car:

For the ceter of the piece, I needed to make brackets. Once again, here's where my recent stockpile of aluminum stock comes in. Here's the beginnings of 8 L brackets:

And here they are on the car. I drilled and tapped holes in the frame rail to mount the bracket to:

To support the rear end of the undertray, I made two more L brackets which bolt to the rear subframe through a hole that was already there. This bracket is vertical, you'll see soon how the ABS goes vertical here:

I probably took this thing on and off twenty times while fitting and cutting it.

There is a section of the exhaust which gets really close to the ABS. Obviously, I love ABS for its ability to be bent and formed once heated up... but that's a double edged sword and won't be good by the exhaust. So, I cut a section out and riveted in an aluminium section for that area:

And here's the near-finished product. The rear area has a lot of bits that I heated up and bent upwards to fit into all the gaps in the rear wheel well to help keep air from getting from the wheel well to the top side of this flat bottom:

Aaaaan mounted. This is the front side, before I made the tongue that goes over that front subframe cross brace to realllly hold the front edge up:

From the back. This center section will join with the diffuser to create a long slick path for air that goes to the diffuser. It will also get vertical sides above it to keep air from the wheel wells off the top of it (those sides are integrated with the new diffuser design:

The piece itself is done, but I am holding off from making a piece that seals off the gap around the oil pan until my new hood vent is done, and the differential is going to probably need a Tilton pump and oil cooler.

-Ryan

 

That's all for now. Hood vent is mid-way done, but it's on hold because I'm having too much fun with the new diffuser

Tomorrow I should have a pic of a Lotus diffuser cut in half!

-Ryan

 

How much was that sheet of ABS and where was it purchased?

 

Thanks guys! This is the stuff that is really fun to work on. I can spend all day and night on this sort of thing (and I have been). So much better than wrenching to fix something that's broken.



I found a great plastics supply place locally called Piedmont Plastics, ~ 10 minutes from my house. They have everything. I'm really fortunate to have found a plastics distributer, metal supply, and industrial hardware supply all within a 10 mile radius of me.

This particular ABS is the most basic of basic types - it's got the one smooth side and one rippled/rough side, and doesn't have any special qualities. $50 for the 4x8 sheet!

For the same reason that I went with some simple L brackets for the undertray, I also went with a cheap ABS; I was not 100% sure how it was going to come out. I've probably crawled under the car five times in the last five years with the intention to figure out how to make a flat underbody and every time have put it off because of the complexity/difficulty and all the associated headaches that could come up. I just decided finally it was happening one way or another, but I didn't want to spend $$$ on materials in case I wasn't happy with how it came out.

That said, I am happy with how it came out so this one will probably be my template for a final version which will be a different material. I am not fully decided on what... I am tossing between Fire and Heat Resistant ABS - which Piedmont Plastics has for $100 per 4x8 sheet, or alumalite - because the aluminum skin would be great for chemical resistance and alumalite has much more rigidity than ABS... But, I can't bend alumalite, so I would have to make the vertical sections seperate and then rivet them to the alumalite... I would also only go with the alumalite if it was thinner than the stuff I have used before - I have 6mm (1/4").. the other drawback is alumalite is more expensive - I think I paid $200 for the 4x8 sheet of 6mm a while back.

There are pros and cons of each, I will probably try to get the weight for each and go with whichever material is lighter!

Oh, I forgot to mention, the whole undertray is 10.5 lbs

very nice! may i ask why you didn't consider covering up the control arms? maybe something removable? or is droop an issue for you?

I don't think droop is an issue - I could look at it tomorrow but I think from memory that you could run the flat bottom under the control arm at full droop.. To be honest I didn't really consider doing that - I was thinking more along the lines of wanting to just make sure the air in the wheel well didn't end up on top of the flat bottom. One benefit of the way I did it, and this is something I was thinking about, was that as-is, the alignment can be done without taking any panels off.

Interesting idea though, hadn't really considered that.

very nice work ryan! you might also want to create an actual skirt that hangs off pinch weld or even the frame rail to keep air from spilling in or escaping out.

Definitely. A guy on Miata Turbo suggested garden edging for this since it's plastic and would be self-clearancing if it scrapes on the ground. I'm going to give it a shot. Will probably mount it to the frame rail since that's sturdy so that if I go bouncing over a high curb in an apex and rip it out, only the edging is damaged, the frame rail would be fine.

I'm considering what to do with said skirt when it gets to the rear wheel well... my first thought would be to curve it inwards, run it between the rear wheel wells, and maybe even connect it with the vertical fins that will be in the new diffuser. The thought there would be that maybe the narrowing area will accellerate airflow. The opposing thought is that pinching the air together might create higher pressure in that section, basically creating lift...

I've seen the undersides of some exotics do some interesting things with either widening or narrowing skirts under the car (usually in the form of a molded composite underbody - those rich bastards! ) but right now I can't remember which it is - widening as it goes back or narrowing...

-Ryan

 

very nice! may i ask why you didn't consider covering up the control arms? maybe something removable? or is droop an issue for you?

 

Too much win in this thread. Way too much!

 

This.

 

very nice work ryan! you might also want to create an actual skirt that hangs off pinch weld or even the frame rail to keep air from spilling in or escaping out.

 

I've considered this, bellwilliam and the guys at slick auto did this too, but in both instances i've seen them partially come off. I haven't drilled ANYTHING into the undercarriage yet keeping a full undertray in mind.

This particular ABS is the most basic of basic types - it's got the one smooth side and one rippled/rough side, and doesn't have any special qualities. $50 for the 4x8 sheet!

For the same reason that I went with some simple L brackets for the undertray, I also went with a cheap ABS;
\
I don't think droop is an issue - I could look at it tomorrow but I think from memory that you could run the flat bottom under the control arm at full droop.. To be honest I didn't really consider doing that - I was thinking more along the lines of wanting to just make sure the air in the wheel well didn't end up on top of the flat bottom. One benefit of the way I did it, and this is something I was thinking about, was that as-is, the alignment can be done without taking any panels off.

Interesting idea though, hadn't really considered that.
-Ryan

Ryan, do you daily the car at all or only TO and FROM? I haven't done anything final to the middle (tranny and driveshaft) due to concerns from drivetrain heat management and the fact that I scrape the frame rails all the time-- and my midpipe's resonator is the lowest piece under the car. I would have liked the floor to be parallel with the frame rails, so the plane can have a rake, starting as early as after the rear floor ends, (much like how Ferrari's diffusers start wayyyy ahead of the rear axles), but I've considered using the frame rails as the main "channel" under the car, and adding material to smooth out everything in between. I had a 2'x3' piece of coroplast after the front subframe, covering the tranny, but it eventually tore off as I went a little too fast over railroad tracks.

Here's a vid of me checking droop and interaction with my lower panels. It is about 1 or 2 inches from the 15x9 et36 (yes those are all season tires). This is at my current 4.0" pinch in the rear (front is 3.75"), I have 2.25" of droop travel and I don't even have to worry about them when it's at full droop (I always keep ease of access in mind).

I have a center channel piece that is under the differential to the rear of the main undercarriage that is about 24" wide, then added these pieces on the sides later on, I think they are 18"x36" trimmed for wheel clearance (and have plenty of clearance).

These side pieces are merely zip tied into place at 3 of the 4 corners, leaving slack room for droop. It hasn't been an issue. The outer rear corners (behind the tire) is free floating and has been for over a year now. It overlaps JJ_Warhorse's WHD1.0 diffuser.

 

dude.......awesomeness!

 

Ryan, would you be offended if I used some of your ideas?!

 

It looks like they spread out towards the rear.

 

Curving inwards of the tire and connecting it with the vane would benefit the aerodynamics. It'll act in a dual venturi tube type of way.

 

Gloriously Badass. Its great to see this DIY stuff. I hope to be going further down this road in the spring.

 

Holy crap...

 

X2! This is insane!

 

Wow, your car reached a whole new level ! Can't wait to get your feedback on this mod.

 

Just finished for the day. There's plenty more left, and I like to post pics of a given project/piece all at once so I can show the steps taken, but I'll put this teaser up:

I said some final words for the Lotus diffuser and then got out the angle grinder:

-Ryan

 

Ryan, the front diffusers are used to move air past the rotating wheel. After moving past the wheel, they are often vented out of the fenders. I believe the reasoning behind that is the rotating wheel creates a sort of wake that acts as a barrier.

 

I'm not quite following..
But, Just to be clear I'm talking about this design: