"MPGiata" modding thread: aiming for 50 MPG with a 1990 Miata. Update: success, 55 MPG!

[MetroMPG]

Originally Posted by Old Tele man

Uh, I'd counter, GF = current "trendy" gotta have bling.

I have not yet had any requests from miataforum.com to mass produce any of these mods.

Are you producing the bumper line straight down? What will the back edge look like?

Yep, straight down. On the inside, it's coming straight back from the tire. All the plan taper is on the outside edge.

Sort of like much bigger versions of the tapered "pie slices" on the lower bumper areas behind the rear wheels of the 2nd gen Prius, or the VW XL1:





Of course theirs aren't as prominent because their rear bumpers were shaped better to begin with.

Will post more/better Miata pics this evening hopefully.

[freebeard]

I'm contemplating a non-Beetle architecture, and it has some similarities.

My thinking is that the underbody flow wants a flat diverter for minimal downforce, but there should be a bell-mouth to couple to the wake. You see those curved indentations in back bumpers to acclimate the consuming public to the idea.

So, a flat roof and curved outer fences with one or two inner fences. The outer fences can merge into a trailing spat, but I incline toward leaving that off to better shed snow and small mammals.

I want to airfoil the twist-beam rear axle.

[MetroMPG]

Originally Posted by freebeard

I want to airfoil the twist-beam rear axle.

YKYAEMW...

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Extensive CAD work.


Driver's side next (it's about half done), then I'd like to do coastdown testing next week. Hopefully this hasn't all been for nothing!

[freebeard]

It looks good, but I'd remove that flat at the rear and curve the inner wall outward.

Consider Fachsenfeld's 'tearing edges'. Here's an aerohead link.

The top of the bumper and the sides form a box cavity. I'd be thinking about how to best feed underbody air into that. Maybe a serrated bottom edge?

edit: Or something like this?

[Stubby79]

Originally Posted by Old Tele man

Excellent spots (left & right) to put LARGE Flamethrowers!

Fixed that for ya.

[MetroMPG]

Both sides done!

Tuft and coastdown testing to come.

[MetroMPG]

Aesthetically questionable, but the air likes it!

[MetroMPG]

PS: does anybody recognize the round logo in the middle of the rear bumper? The car had a bunch of stickers on it when I got it, but that one needs more persuading to remove.

I struck out trying Google image search with upload.

[MetroMPG]

From what I saw, flow is attached along the full length of the skirt with minor exceptions:



Once in a while, the last, lowest tufts get a little crazy, but flow never reverses.

Compare to a non-skirted, non-wheel-disc Miata:



Artist-enhanced! Because he didn't put on as many tufts. But view the video, and I don't think you'll disagree with the artwork: There's zero attached flow on the bodywork behind the wheel arch/tire.

Last test: tomorrow may be nice enough to do some coastdown comparisons.

[MetroMPG]

A little less ugly?