Terrh

iTrader: (7)

So I had an idea.. you know how there's the big plastic front undertray, and then the aluminum one on some cars..

How about taking that idea further back along the chassis inbetween the framerails?
If you've ever looked at the bottom of a ferarri F-40 (or just about any other supercar) (or detailed model) - you'll notice that most of them are VERY flat along the bottom, I'm sure this has big aerodynamic benefits as well..

Think this is worth the effort? Will I turn my car into a big flying wing and leave the ground at 120mph? Or will it stick to the ground and be wonderful?

vipers

iTrader: (8)

its usually on supercars that exceed 200+ mph........ unless you plan on running 150+ mph it wont be very effective, and a waste of time and money.......

classicauto

iTrader: (3)

I agree about the speed factor....

But he does have a point...some of the new Lexus'(I think it was lexus...anyways one of those luxury types) have dimpled floor panels to create an effect similar to a golf ball aerodynamically.

but holy snapper!.... it would it be a lot of work

jgrewe

iTrader: (1)

Two words: Exhaust heat.

Terrh

iTrader: (7)

I don't think that exhaust heat would be /much/ of an issue, I have no cats and heat rises, not falls...

takahashiRyosukeFC3S

if you look at those super cars and some not so super like the Lexis mentioned they creat a more smooth flow of air and less wind resistance under the car. This help in the racing world because you can split the air at the front of the car so there is neutral pressure under the car but in the rear you create a ventury effect that litterally sucks the car to the road via vacuum. See picture. a small amount of air need to fit a LARGE void = VACUUM.

TR

oakback

Also helps with noise. Less wind resistance, less noise. That may be why you see it on nicer cars that you wouldn't think go over 150 on a regular basis.

trochoid

iTrader: (6)

Yes heat rises, but the heat from the exhaust piping also radiates 360*. If you put heat in a box, the entire box heats up, not just the top.

Icemark

Actually the underpan for under the oil pan is one of the things that help drop the Cd of the Sport get down to .29 instead of the .32 found on most other coupes.

Note the above picture is not to scale. The front pan (labled 56-1-11B) is considerably bigger than the aero cover (labled 56-11Y)

takahashiRyosukeFC3S

unless you factor that into your under tray.

fr wheel inlets to cool Outlets rr wheel Venturi
| | | | | | | |
----(__)---/ /-----/ /------------------\ \-----\ \--\ \--(__)--------/

the inlet scoops add a controled stream of air to cool the exhaust and the outlet ducts allow heated air to escape. you'll want slightly larger or more outlets to keep a vacuum in the "box" you have now made for the exhaust. this vacuum makes the inlet scoops do their job by constantly sucking in new air.

jana,
TR

KeloidJonesJr.

iTrader: (8)

defuser

Terrh

iTrader: (7)

any other input?

thanks everyone, I think it's worthwhile.

iceblue

I thought of it for years. IE all F1 cars are this way.

Anyhow Porsche did a study as you know they most all hit over 200mph. They found at higher speeds the wind traveling under the car creates a N magnetic field. This occurrence caused the cars to lift from the ground. In order to combat this they roughed special ducts to + charge the chassis, this reaction caused the car to be sucked down and stock much harder.

If I am not mistaken F1 cars do or used to + charge their cars. This is not voltage this is magnetic charges. They may have over come this now days with the amount of down force and added technology.

Just so you know this would be around 700$ in aluminum sheet metal.

swanton187

less drag = a bit better gas mileage

Terrh

iTrader: (7)

$700 would buy /me/ enough metal to bulid a whole car..

and I'd probably be making these out of CF, since I'm wanting to do some experimenting with it and it would basically cost me nothing (since I'd be making stuff with it anyways).. but aluminum is certainly a possability.

gas milage = I don't care
less drag for better accellertion and top speed = teh win

so yeah, I think I'd be doing this, yes.

iceblue

^ ever priced sheet metal? You should give them a call.

Aaron Cake

iTrader: (1)

The Honda Insight comes from the factory with a full undertray, which of course is done for the aerodynamic benefit (Insight has a 0.23 CoD making it the most aerodynamic production car in the world). However, this tray can make the car flightly at high speeds...of course these are speeds MUCH higher then legal in anywhere North America...Obviously this characteristic could be a problem with the FC but since it's a car shaped totally differently then maybe the results won't be quite the same.

Exhaust heat isn't much of an issue if you leave a channel down the middle of the tray for the exhaust to pass through.

However I must point out that if you drive the car in the winter the tray can be a major pain in the ***. It WILL get hung up and it WILL get torn. I have had to replace parts of the Insight's tray every year.

Terrh

iTrader: (7)

yeah, I've built many many things out of metal.
you can pretty much spend as much or as little as you want, it all depends on where you look and who you know.

My ex-boss spent $600 on a piece of stainless steel, I just purchased a similar one for $50.. and mine is better steel!

doesn't matter anyways, I'll probably make them out of CF. I am concered about the lift though so I'll probably make prototypes out of aluminum and see how it goes before I make the final ones.

I don't drive my rx7 in the winter lol! You should know that aaron that's whate beaters are for!

Tech_Greek

I was thinking of this the other day, making a full under tray would get rid of a lot of drag (and watching it on the history channel on the history of race cars) because there's no fuel lines, etc, for wind to bounce off of.

I got bored and thought about making a full one on my car, I don't think it would be that hard, it's just a matter of tracing the pattern out and drilling for the appr. bolt holes.

RotaryEvolution

iTrader: (30)

i would rather allow my engine to breathe rather than worry about drag at 150MPH which it will hardly ever see in it's life.

Tech_Greek

If you felt how hot my engine bay gets, then you look for solutions...one of which would be the vacuum effect of the air getting pushed out of channels (from the engine bay) to the rear past the exhaust and have fresh air pushed in via a hood scoop and you have one cool engine bay.

RotaryEvolution

iTrader: (30)

if you say so, making the air have to exit further back, i dont see how it helps keep the bay cooler.


your hood scoop is what allows the engine bay to cool, not adding more undertrays.

vipers

iTrader: (8)

again i say...... unless you plan on running 150+...its pointless

the gas mileage would be minimal in gains

if its done in metal, the weight would counter the benefits of the tray

most vehicles w/ undertrays have been wind tunnel tested for safety and effectiveness, just because you make you car smooth underneath doesnt mean anything, you still would need the proper wings, canards, diffusers to make your car stable at high speed

Tech_Greek

Yes,

Exactly, the hood scoop would make it cool easier, and I intend on getting a TII hood just for that reason BUT that hot air has to go somewhere, why not make it exit out the back?

It's the same concept as the exhaust...why not just let it exit in the engine bay - because heat is bad and you want it as far away from the engine as possible.

It's the same way a PC Case works with fans, you have an intake and exhaust fan, one sucks in and the other blows out...

Twofer

Eh, you're going to have to point me to that article, because I'm pretty sure this only has to do with aerodynamics.

Wing


Car


Lift
http://www.allstar.fiu.edu/aero/lift-anim.htm
http://www.nas.nasa.gov/About/Education/Racecar/
http://travel.howstuffworks.com/airplane6.htm

Now, I haven't put the Audi TT Coupe concept in a wind tunnel, but you can see how cars are roughly wing shaped. (Air flows faster over the top than it does under the car.)

The underbody cover would be to reduce drag from the air hitting all the crap (fuel lines, exhaust, oil pan, etc...) under the car.

Spoilers, like the one on the Turbo II, slow down the air comming over the car thereby reducing lift. With a decent angle of attack, it can go further and produce some downforce.

GT style spoilers are actually inverted wings which produce downward (negative) lift.

Deck lip spoilers, like the 7's Sport Spoiler smooth out the transition from "air going over the car" to "air filling the void behind the car", and reduce drag. (But have little effect on downforce.)

I remember from a Best Motoring episode, (BMI Vol 6 "The 350 Z Shock!!!") that the new 350Z is designed with a "Zero Lift" concept. No downforce, no lift. The idea being that the car, aerodynamicly, handles the same at any speed.



On a side note, that's a good episode of BMI, and even if you don't like 350Z's, you have to admire the work Nissan put in to it.

Sorry, I get a bit carried away with the science stuff.