Wind Chart/Diagram, How's It Look? Options

[Bigmeanbulldog55]

I was driving back to college from home, and it was raining out. I noticed that the back glass kept dry even in the heavey rain. This just made me curious to see a wind chart for the celica. It's a hachback with a wing. Any have this? And I was also wondering how functional this wing really is? Any know? Thanks.

[SinisterWhisper]

what wing? if it is the two post it doesn't do much unless you get gt4 blocks to raise it up dunno about the 3 post though

[Stealths95GT]

the gt4 posts work pretty well...but it isn't rwd so it is effectively useless...i know i had one...does better without the spoiler

[playr158]

spoilerless RULES

stock spoilers never do anything

[orvillescelica]

spoilers and wings are two different beasts. A wing creates downforce and are thus useless on fwd cars like ours. But a spoiler is meant to distrubt the airflow coming off the back of the car. It effectivly decreases the coefficent of drag by as much as .05 . Im not in the car areodynamics biz, so i dont know exactly the dynamics that are invovled but i have two theories by just thinking about it.

1) Airflow coming off the roof that is slowed from friction with the car (an area of airflow known as the 'boundary layer') seperates as it decends from the roof down the hatch. This flow becomes turbulent. But the seperation is low enough that the turbulent boundary layer reattaches on the spoiler and the properly flows off the back. This keeps the effective flow above the boundary layer streamline with the end of the car, and thus a lower coefficent of drag.

2) The spoiler controls the angle of the flow coming off the end of the car, creating a more exagerated vortex that is known as the 'Kutta Condition.' Since this vortex is bigger and has a greater moment, the fixed vortex at the front of the car must also be bigger to balance it out. This pushes the stagnation point (the front o fthe car where the forward coming air hits) lower, and thus the air must 'swoop' upward to go over the hood. 'swooping' creates a negative pressure area at the front of the car, creating a force the counteracts drag. Thus the overall coefficent of drag is decreased.

Assuming only one of my theories are true. The reason why rain does not hit the back of window as much can be explained by my first theory. Since the effective flow follows the boundary layer, and it is dettached at that point. Any rain particles at low velocity will be swept up in the effective flow at higher velocities. So the rain is swept away by the flow and does not hit your car.

of course, like i said, im not in the car aerodynamics business. So this is all speculation. The aerodynamics i deal with, our cars would have to travel at Mach 6.

[Bigmeanbulldog55]

I'm afraid that even if there isn't any down force needed because I'm FWD, there is still some stability added with the wing. And it is the two post, like the gt-4 without the blocks. I drive at high speeds fequently (interstate travel), and I'd like to get this thing as stable as possable. Would the blocks help? I'd have to at lest get some side skirts if I got the blocks, so there's not going to be a big change of that right away. But it's still nice to know these things.

[Hanyo]

the spoiler has something to do with this.. (sorry for the bad drawing.)




the car on the top has a spoiler.. and the car at the bottom doesnt..

As you can see.. the spoiler breaks the air further away from the end of the car. So the vortex ( swirly air) starts spining farther away from the car. The faster the air moves (more swirly) the more suction or drag it will create.

[orvillescelica]

Thanks Hanyo for sheding some light on it for me. Based on your picture, that goes along with my first theory. Since the distance of the vortex from the body is poportional to the boundary layer seperation distance, the spoiler must allow for reattachment of the boundary layer on to the spoiler, and then re-detaching off the spoiler. Or promotion of no detachment at all. This would cause the resultant vortex to be further from the car since the dettachment distance is now further. This both decreases the suction force near the hatch window due to reattached flow (no vortex due to dettachment), decreasing the coefficent of drag, and also it would detour lift at the rear wheels since there is less chance the vortex would swoop under the car since it is further from the body.

Thanks to Mynzeyes for lending his car for this demonstration, i hope he doesnt mind.





This post has been edited by orvillescelica: Feb 15, 2005 - 5:08 AM

[Akimbo]

Here I'll type up what I have from this book.

As the name implies this device spoils the airflow over the top half of the car t the trailing edge of the car's upper surface. The spoiler can keep airflow from tumbling and creating a swirling vortex behind the car. This is important for a couple of reasons - without a spoiler, siwrling air behind the car can create both;
-Drag (which can keep the car from moving forward as quickly as possible). Drag is expressed as a numeric coefficient of wind resistance.
-Lift (which reduces the car's grip on the road at speed)

Manufacturers have been known to add spoilers to cars that didn't have them in the original design. The Audi TT was released first without any spoiler. It could only be purchased with a spoiler after reports began deriding its high-speed stability and inherent rear lift.

-Wings-
A WING on a car is an upside down version of the wing on an airplane. Instead of lifting, the upside-down pushes the car against the ground.
Because the wing must catch an undisturbed flow of air, most wings are mounted on raised pedestals.
Many wings can be adjusted for rake (vertical angle) so that the amount of downforce (and corresponding drag) can be fine-tuned for a specific application. This is often accomplished with adjustment holes that allow you to alter the angle of the wing's plane for adjustable levels of resistance.

Got that from Car Hacks & Mods for Dummies by David Vespremi.

[Bigmeanbulldog55]

All that is great guys. Most of this stuff I knew, sorry. I do appreciate everyone typing up these things though. But does our wing/spoiler do this? or is it just for looks? Does anyone have a set up that seemed to help. I took the wing off of my last car (Isuzu Impulse), and it drove better without it. It actually was causing more drag and less stability at high speeds, at least it felt like it. I guess I could just take my celica wing off and see what it does. Don't know why I didn't think of that before.

[CoSo]

http://freespace.virgin.net/shalco.com/tte_ST205.htm

This article may shed some light on the matter. This is for the GT-FOUR rear spoiler however. In particular:

The purpose of the rear wing is to correct the inherent balance disadvantage of a transverse-engined car compared with longitudinal-engined models like Fords and Subaru's. The aerofoil has been designed to minimise drag losses while still increasing the downforce and it is effective from 100-120 kph upwards.

"We get better traction and it makes the car more stable. The wing has two positions, up and down, with removable distance pieces. In the Japanese market it will be sold with the wing in me up position and the pieces in place, but to help transport the export cars the pieces will be removed and stowed in me boot ready to fit on arrival. "We are expecting to sell around 2500 examples in Japan alone with the pieces in place. The amount of downforce is influenced by ride height and we still have to carry out wind tunnel tests, but it's expected that there will be 50 kg of downforce at 100 kph with the wing in the up position, and maybe five times more than that with the wing at the low position."

This post has been edited by CoSo: Feb 15, 2005 - 12:00 PM

[dutchboy]

http://freespace.virgin.net/shalco.com/tte_ST205.htm

This article may shed some light on the matter. This is for the GT-FOUR rear spoiler however. In particular:

The purpose of the rear wing is to correct the inherent balance disadvantage of a transverse-engined car compared with longitudinal-engined models like Fords and Subaru's. The aerofoil has been designed to minimise drag losses while still increasing the downforce and it is effective from 100-120 kph upwards.

"We get better traction and it makes the car more stable. The wing has two positions, up and down, with removable distance pieces... The amount of downforce is influenced by ride height and we still have to carry out wind tunnel tests, but it's expected that there will be 50 kg of downforce at 100 kph with the wing in the up position, and maybe five times more than that with the wing at the low position."

According to this, my understanding is that the 2-post spoiler produces more downforce without the GT-Four riser blocks.

My question is, is all this downforce really necessary on the lighter engined ST?

Will the ST be better off with or without the spoiler, from a drag/ fuel economy standpoint?

If you can point me to other such discussions, it would be appreciated