Underbody aero

[wytbishop]

I didn't mention them together to imply that CFD and FEA are related...merely to suggest that they have a similar level of complexity.

[Ryan]

Oh, then yes You're absolutely correct.

[Josh]

For those who can read this some interesting information

http://www.v6calibra.net/docs/calibra_a ... ynamic.htm



And another great article

http://www2.mech.kth.se/courses/5C1211/Drag04.pdf

[Josh]

And a good video of the Lotus

http://www.youtube.com/watch?v=_BnHXfvZ ... embedded#!

[SgtLynch]

The MX 3 is actually a really good candidate out of the box for making a flatbottom car... moreso then a Mustang anyways. Most of the stuff under the car is tucked up so you don't need to re-engineer everything under the car. The rear suspention is the biggest area of parts that you won't be able to move and will cause turbulance.

There is enough information here on the subject to build the entire thing from scratch, great post. The only thing I can add is the difuser needs to be loooong. the farther back (under the car) you can extend it the better. It needs a gradual curve (about 10deg) to it, and the thoat (exit) should be straight for at least 5 inches. A cross section of it should look like a very gradual "S" almost. On the MX3 the difuser should start right after the rear tie bar.

I built a flat bottom Mustang and it worked. Most of the information I worked from was Formula one based information sites. I bought two plastic model kits... an F1 car and a GT car and looked at those.... sounds silly, but it was helpfull to see something in 3D instead of pictures. What I eventually ended up with was probably 50% fluke and 50% understanding. What I learned is, the front splitter angle drastically effects the rest of the system. It needs to be level or slightly angled down. Above level and it obviously produces lift, too high an angle of attack and it fails to accellerate air, I think an air pocket or something forms right past it and air turbulates or spills out the sides. (no windtunnel.. sorry)

Last, once you manage to build all that, your next issue is suspention. The car needs to run no more then 1-1.5" off the ground for ground effect to work. Say goodby to ride quality, you need to set up the suspention for maintaining rideheight. Stiff springs, adjustable shocks (med compression/stiff rebound) bumpstops, and thick swaybars are a minimum.

[bmagera91]

I build and install a number of these in my car to see how it works. I'll make a glass fiber.

But you do not think sealing the bottom of the car, the engine heat up more?

[SgtLynch]

I build and install a number of these in my car to see how it works. I'll make a glass fiber.

But you do not think sealing the bottom of the car, the engine heat up more?

Everything will loose airflow under the car, so some type of airflow has to exsist for motor/transmision, headers etc. NACA ducts under the car work well to get air to specific areas.

[jaydog is back]

The splitter and ride height will need to be dialed in. The most important part of the undertray is that it must be raked as well as smooth. The front must be lower than the rear. To what degree and angle of the rear diffuser will need some testing..I'm working on the undertray development. It will benefit the car when you are moving at 130+mph.

[kulluminati777]

sounds good for the autobahn

[Josh]

Well seeing as though the RS tops out at 132 or so, mine topped out at 136 looks like I am SOL

[MrMazda92]

I got my '92 w/ K8 up to 122 once... Scarier than hell, I hated the feel above 115. 110 wasn't so bad though...

[Mooneggs]

I'm still interested.

[kulluminati777]

yeah i would love undertrays on my car...i dont thik much "testing" would be need cut the correct cut so we can bolt it on with holes to let hot air escape.

[Josh]

I have been looking at factory aero trays from newer FWD cars, and you will need a series of vents just behind the rad and the trans and engine. other than that you could flat bottom the rest of the car smooth until you got to the rear. To do the rear properly you will almost need to cut the rear bumper cover higher to make a proper rear dam. Depending on the material you use I think it is more form over function, but its cool to say you have it.

Sam needs one made out of steel for as low as he is sitting

[mx3matt]