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Assassintime14 03-07-2019 11:46 AM

Hey guys I'd love some recommendations (2017 Mitsubishi Mirage)
Hey guys, I'm a member from I'm that kid that blew up the motor after 6900 miles on it, and I'm doing a capstone project for my CADD engineering class. My current plans include improving the aerodynamics for better fuel economy and less drag, and hopefully removing the annoying act of the wind pulling my steering wheel from me on windy days. I currently would like to design a front splitter and air dam, a kammback extension, and side skirts at least. I do have some cash to spare to actually fabricate the parts, and help on how to mount and make my parts is greatly appreciated. I have looked around here at some work that people have done and I can't wait to hear back from you guys! Also, this is my first post here :)

kach22i 03-07-2019 12:22 PM

Assuming this is your little blue egg.

AssassinTime14's 2017 Mitsubishi Mirage ES "少し津波 (Little Tsunami)"
Got her a bit muddy from enjoying an empty gravel parking lot
Similar to this:

Side view for template overlay:

Please verify.

In the future it would help if you provide such graphic information up front so that respondents can spend their time helping you and not hunting down information that should have been provided.

I don't mean to sound short with you, but it's lunch time and I have to go.

Check out the sticky's in this section of the forum and do an overlay using the aerodynamic template. This little exercise will help you to help yourself.

Good luck.

Assassintime14 03-07-2019 01:23 PM

1 Attachment(s)
Indeed that is my little car, I no longer have the hubcaps which would have been very helpful for this project. Here is a mirage with that overlay over it.

Attachment 25605

Also I have AutoCAD and Solidworks at my disposal for this project.
Sorry for not posting pictures to go along with my first post.

freebeard 03-07-2019 01:51 PM


I'm doing a capstone project for my CADD engineering class.
Does your project have a defined use case? (urban vs freeway vs time attack)


I have looked around here at some work that people have done and I can't wait to hear back from you guys!
What have you seen that you liked?

kach22i 03-07-2019 02:39 PM


Originally Posted by freebeard (Post 592991)
Does your project have a defined use case? (urban vs freeway vs time attack)

What have you seen that you liked?

Good questions.

I had to look some of this up, perhaps our original poster can lend further definition.

Capstone course


Not that it matters, but I'm assuming you are in Ohio, is it a "engineering" school or more of a "design" school and curriculum?

You looking to innovate or replicate?

Break new ground or rely on the tried and true?


Please find and post your Cd (Coefficient of Drag) baseline starting point.

For such a short car, yours look like it's ahead of most right out of the factory.

Vman455 03-07-2019 10:24 PM

There's an aerodynamicist for one of the OEMs who posts occasionally on Jalopnik and TTAC; according to him, mudguards are always a drag hit, so I would remove those first. Also according to him, air curtains on the front wheels are usually worth about -.005 CD; you could use the fog light blanks as intakes for these and then crib the ducts off something like an Ioniq for less than $15.

Get rid of the exterior mirrors and their associated interference drag and frontal area; you can remove both legally in Ohio. Replace with something like this:

...or cameras if you feel like and your budget allows.

If you don't have grill shutters (I don't remember if the Mirage does or not), block as much of the grill as you can without affecting coolant temperatures. Scangauge, Torque or similar will be useful to get accurate temperatures directly from the OBD.

For improved lateral stability, I would try something like what Toyota does, with fins on the underside of all their cars that they say specifically improve highway stability. Here they are on the rear diffuser of the 2020 Corolla Hybrid:

Toyota has switched to a 4-fin design from the earlier 2- found on the Sienna, Prius, etc. This is something you could model in CAD and test size/placement. Similarly, if you end up adding any sort of spoiler extension, you can add stabilizing fins there as well, like Lucid did on their record car:

Any tapered extension you add at the rear will likely reduce drag; again, something you could model in CAD and test.

If you can get a copy of T. Yomi Obidi's Theory and Applications of Aerodynamics for Ground Vehicles (you can find it on Amazon), it has an entire chapter on vehicle stability you may find useful, in addition to the rest of the book which is quite thorough.

Assassintime14 03-08-2019 02:40 PM

2 Attachment(s)
The use case for me is pretty much for a daily driver and for taking to auto crossing In the following months hopefully.

According to Mitsu's press release "These aero enhancements help the 2017 Mirage achieve a very low coefficient of drag at only 0.27 (Cd)."

The projects I've liked are are the partial kammback on that geo metro hatch, and some of the air dams you guys have created.

The Capstone is to prove that me, and my team can follow the engineering design process. I'm fine with using tried and true designs since it will be a bit easier.

For a front splitter, I'm becoming a fan of this one from

Attachment 25608

Attachment 25609

Making some fans to act as a rear diffuser would be probably easy to model and produce.

freebeard 03-08-2019 03:52 PM

Thanks for responding. Your words say daily driver, but your attachment says time attack. :)

I like the splitter too, but it would be an encumberance around curbs and speed bumps. That white airdam alone, with a notch in the middle to create a central jet in the underbody would be more livable.

If you do have a splitter like that you'd want a difusser to match.
It doesn't show at that angle, but the sidewalls of the difusser on the Corvette start inside the tires and bell out to the outer face of the tires. This IMHO create an exponential horn on the inside and plows the wheelwell turbulence outward. The Lotus' fans out, but only to half the tires width and they're flat.

Consider Aerocivic-style side fences or wheel spats. Or front-wheel air curtains.

kach22i 03-08-2019 04:33 PM


Originally Posted by Assassintime14 (Post 593113)
The projects I've liked are are the partial kammback on that geo metro hatch, and some of the air dams you guys have created.

I think you have the right idea by keeping your goals simple and similar to what we might call standards in the forum.

Doing less well rather than a lot poorly will hopefully show maturity and professionalism resulting in a better grade and end product.

The Kammback you have in mind, can you please provide a link and or image of the Geo metro hatch?

As far as the chin spoiler, in my signature there is a link to the one on my S10 pickup truck. However recently someone did an excellent job of one, and the splitter is more modest so it might not be such a problem on inclined drives and speed-bumps.

New front dam, splitter, undertray install.

freebeard 03-08-2019 06:37 PM

I was trying to find an example someone posted of a conveyor belt airdam with a central notch. No success so far but I did run across these examples I hadn't seen before:

Spats, skirts and a truncated boat tail vs standard Ecomodder mods.

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