Best spoiler (Purpose not looks):Pling:

[jagman]

Ailerons operate to both increase lift and decrease lift , so one wing moves up and the other down , ie one aileron goes up and the opposite wing goes down.

[jagman]

To answer the OP,s question , for effective down force the rear spoiler is actually a rear wing but upside down, so lift is negative and related to the square of speed, but to work has to be in clean air ie a couple of foot higher than the car body- hence the daft looking elongated struts such things are on.

For effective turbulence control the spoiler is nearer the body , the stock one is probably a mix of both , but more geared to fuel saving than downforce.

[Morpheus]

Ailerons operate to both increase lift and decrease lift , so one wing moves up and the other down , ie one aileron goes up and the opposite wing goes down.

 

Indeed, of course.

 

My whole issue here is to get across that spoilers on factory cars reduce drag but everyone's on about increasing it.

 

 

Anyone have any more figures for the OP to digest? Alex reckoned 90lbs for stock but at what speed? Might ask him....

[Morpheus]

To answer the OP,s question , for effective down force the rear spoiler is actually a rear wing but upside down, so lift is negative and related to the square of speed, but to work has to be in clean air ie a couple of foot higher than the car body- hence the daft looking elongated struts such things are on.

For effective turbulence control the spoiler is nearer the body , the stock one is probably a mix of both , but more geared to fuel saving than downforce.

 

See everyone, my 'huge' Bomex is better than stock! Ha!

 

The weight alone should give 200lbs of downforce, I reckon!

[swandip]

Or you could put a bag of cement in the boot.

[Smallshinyant]

well to add some figures to the mix, it seems that the the drag coefficient figures on a supra are changed slightly by the stock rear wing.

 

0.32 Toyota Supra (N/A with wing and turbo models) 1993

0.31 Toyota Supra (N/A; without factory wing) 1993

 

http://en.wikipedia.org/wiki/Automobile_drag_coefficient

[Guest Snaps]

Adding anything to the shape of a car will increase drag. The most aerodynamic shape I would think would be a needle or bullet (isn't that why a bullet is that shape - for the least drag and therefore the most range?).

 

The other thing you need to think about is downforce, any place where the pressure above the plane (not plane as in aircraft, but plane as in 3D line) is higher than the pressure below the plane you will have a force created, this is the point of a spoiler or wing, to create a force downwards to give more traction for turning, braking and high speed stability.

 

A rear diffuser is used to 'fill in' the low pressure air or drag behind the car, created by the car moving, this decreases drag and increases fuel economy, while the low pressure under the car (created by the flow of air out to the back of the car by the diffuser) will pull the car down, once again giving more downforce.

[steady_dave]

Adding anything to the shape of a car will increase drag. The most aerodynamic shape I would think would be a needle or bullet (isn't that why a bullet is that shape - for the least drag and therefore the most range?).

 

The other thing you need to think about is downforce, any place where the pressure above the plane (not plane as in aircraft, but plane as in 3D line) is higher than the pressure below the plane you will have a force created, this is the point of a spoiler or wing, to create a force downwards to give more traction for turning, braking and high speed stability.

 

A rear diffuser is used to 'fill in' the low pressure air or drag behind the car, created by the car moving, this decreases drag and increases fuel economy, while the low pressure under the car (created by the flow of air out to the back of the car by the diffuser) will pull the car down, once again giving more downforce.

 

As much as I thank you for this post, I did not ask what downforce is. I just want figures of which produces more, TRD or standard.

[TLicense]

lol, no-one knows though Dave - and unfortunately this thread has been hi-jacked by a lot of people who don't seem to know a great deal about what they're talking about!

[lust2luv]

The claimed downforce of the stock spoiler is apparently 66lb @ 90mph.

 

Road & Track article

 

[TLicense]

A rear diffuser is used to 'fill in' the low pressure air or drag behind the car, created by the car moving, this decreases drag and increases fuel economy, while the low pressure under the car (created by the flow of air out to the back of the car by the diffuser) will pull the car down, once again giving more downforce.

 

Very wrong I'm afraid. Any diffuser is going to INCREASE drag and therefore DECREASE fuel economy, but connects the low pressure region at the back of the car to the air-flow under the car.

It's quite simple. MORE LIFT = MORE DRAG = LESS FUEL ECONOMY.

In the 12 years that I've worked with vehicle aerodynamics, I've very rarely seen anything that generated more lift and was a drag benefit.

[Mcgoo]

The claimed downforce of the stock spoiler is apparently 66lb @ 90mph.

 

Road & Track article

 

 

Good find.

[steady_dave]

The claimed downforce of the stock spoiler is apparently 66lb @ 90mph.

 

Road & Track article

 

 

Ah nice one, thank you soooo much this is just what I was looking for.

 

It's very doubtful that the TRD spoiler figures have been published so how would you go and test something like this?

[steady_dave]

lol, no-one knows though Dave - and unfortunately this thread has been hi-jacked by a lot of people who don't seem to know a great deal about what they're talking about!

 

Lol yeah i've noticed this, cheers for your input though! I have learned a lot from this thread!

[Morpheus]

Ah nice one, thank you soooo much this is just what I was looking for.

 

It's very doubtful that the TRD spoiler figures have been published so how would you go and test something like this?

 

Oh, you just wouldn't let it lie! Hehe!

 

I like you; you remind me of myself!

 

Firstly I'd contact TRD but failing that, if you really wanted to be anal about it, (my specialist subject - ooer!), one way that springs to mind could be to measure the standing height of the car on the road at the rear diff. or bumper lip somewhere convenient with driver in car and then fix up two keyring or pocket laser pointers about a foot apart and aiming toward eachother (Barnes Wallace stylie!) to meet at the same point on the ground, then setup a remote camera (ebay, circa £30 with fixing bracket and focus adjustment with receiver or use a hardwired parking camera into dvd player etc.) to view the difference in the beam distance unladen and at say 50-75kg by using various loads, e.g. barbell discs or bags of sand or cement , to increase the weight of the rear - must be at the very back under the spoiler.

 

Once you've setup the camera to give a reliable reading of distance and therefore weight, remove the added load and your stock spoiler, then drive at 90mph (on a private track, of course ) and record the camera view of the light beams and calculate the downforce achieved at 90mph from the original deflection. Maybe just use masking tape on the dvd or laptop screen to create a useable scale? Everything should be fixed solid and should be quite reliable if done well. The smoother the road the better, of course!

 

Then fit the stock spoiler unladen and restest, then the TRD unit and retest (again at 90mph) and you'll see the difference. I'd keep fuel very low in the tank as it should give a greater and therefore easier to read differential in the beam convergence as the springs will move more at the top of their range than under heavy load already. By comparing the stationary height at various weights to the original measured height at the bumper or diff. etc. and the image on the camera, you can zero in on the exact downforce achieved, depending on your care in setting the camera and beams up.

 

Simple enough in principle but easier said than done, I'm sure!

 

You'll need a laptop or in-dash Dvd with composite vga (yellow phono plug) input or via an adapter, a remote camera, maybe a parking one, two laser pointers, 2 or 3 bags of sand or cement @ 25kg each (only £3 each) and lots of patience but you've proven that already!

 

Good luck!

Edited July 5, 2010 by Morpheus
Keep forgetting stuff! (see edit history)

[Dnk]

firstly i'd contact them but failing that, if you really wanted to be anal about it, one way that springs to mind could be to measure the standing height of the car on the road at the rear diff. Or bumper lip somewhere convenient and fix up two keyring or pocket laser pointers (barnes wallace stylie!) to meet at the same point on the ground, then using various loads, e.g. Bags of sand or cement , increase the weight of the rear - must be at the very back under the spoiler - to say, three bags or 75kg and setup a remote camera (ebay, circa £30 with fixing bracket and focus adjustment) to view the difference in the beam distance at that load.

 

Then once you've setup the camera to give a reliable reading of distance and therefore weight, remove the added load and your stock spoiler, then drive it at 90mph (on a private track, of course ) and record the camera view of the light beams and calculate the downforce achieved at 90mph from the original deflection. Maybe just use masking tape on a laptop screen to create a useable scale? Everything should be fixed solid and should be quite reliable. The smoother the road the better, of course!

 

Then fit the trd unit and retest at 90mph and you'll see the difference. I'd keep fuel very low in the tank as it should give a greater and therefore easier to read differential in the beam convergence. Simple enough in principle but easier said than done i'm sure!

 

You'll need a laptop with vga input or via an adapter, a remote camera, maybe a parking one, two laser pointers, 2 or 3 bags of sand or cement @ 25kg each (only £3 each) and lots of patience but you've proven that already!

 

good luck!

 

pmsl

[steady_dave]

Firstly I'd contact them but failing that, if you really wanted to be anal about it, one way that springs to mind could be to measure the standing height of the car on the road at the rear diff. or bumper lip somewhere convenient and fix up two keyring or pocket laser pointers (Barnes Wallace stylie!) to meet at the same point on the ground, then using various loads, e.g. bags of sand or cement , increase the weight of the rear - must be at the very back under the spoiler - to say, three bags or 75kg and setup a remote camera (ebay, circa £30 with fixing bracket and focus adjustment) to view the difference in the beam distance at that load.

 

Then once you've setup the camera to give a reliable reading of distance and therefore weight, remove the added load and your stock spoiler, then drive it at 90mph (on a private track, of course ) and record the camera view of the light beams and calculate the downforce achieved at 90mph from the original deflection. Maybe just use masking tape on a laptop screen to create a useable scale? Everything should be fixed solid and should be quite reliable. The smoother the road the better, of course!

 

Then fit the TRD unit and retest at 90mph and you'll see the difference. I'd keep fuel very low in the tank as it should give a greater and therefore easier to read differential in the beam convergence. Simple enough in principle but easier said than done I'm sure!

 

You'll need a laptop with vga input or via an adapter, a remote camera, maybe a parking one, two laser pointers, 2 or 3 bags of sand or cement @ 25kg each (only £3 each) and lots of patience but you've proven that already!

 

Good luck!

 

One day i'm going to do this and then I shall have the last laugh, lol.

 

Yeah might give them a ring.

 

Do they have a UK office or would I have to call America?

[jagman]

Doubt there much difference , the spoiler areas are similar ,so its down to the Coeffcient of lift for any changes between spoilers -

As the CofL is unknown makes it tricky

However you do know the downforce on stock so you could calc its CofL and see how close to maximum it is or how much margin there is left

[Dnk]

Doubt there much difference , the spoiler areas are similar ,so its down to the Coeffcient of lift for any changes between spoilers -

As the CofL is unknown makes it tricky

However you do know the downforce on stock so you could calc its CofL and see how close to maximum it is or how much margin there is left

 

How are they similar, a TRD wing is nothing like the o/e wing

Edited July 5, 2010 by Dnk (see edit history)

[Morpheus]

Hey, I noticed that quoting someone adds and removes capitals!

 

My final draft is below quoted ones btw. and contains no such errors.

 

TRD must be easily found, hang on.....

[Morpheus]

Here's their USA 'Contact Us' page....

 

http://www.trdusa.com/contactus.cfm

 

 

This may be more or much less useful.....

 

http://www.trdparts.jp/english/distributor.html

Edited July 5, 2010 by Morpheus (see edit history)

[Guest Snaps]

Very wrong I'm afraid. Any diffuser is going to INCREASE drag and therefore DECREASE fuel economy, but connects the low pressure region at the back of the car to the air-flow under the car.

It's quite simple. MORE LIFT = MORE DRAG = LESS FUEL ECONOMY.

In the 12 years that I've worked with vehicle aerodynamics, I've very rarely seen anything that generated more lift and was a drag benefit.

 

I was meaning a rear diffuser if that wasn't very clear.

 

Do you agree that there is an area of low pressure behind the car when it is traveling at speed? If so, then you should believe that increasing that pressure in relation to the pressure at the front of the car will cause a frontward force (well, really it's causing less of a pulling force) to act on the car due to the lower difference in pressure? This means the car has to use less fuel to travel at any speed.

 

Another way to think of it would be like wind acting on a car, wind hitting the front of the car would cause a force to be acting on the car, pushing it backwards, yes? And wind hitting the rear of the car would cause a force to act forward on the car? Same principle here, if there is less vacuum pulling the car backwards (i.e. more 'force' pushing it forwards), the car will use less fuel.

 

That's what a properly set-up rear diffuser is made to do, funnel air into the low pressure area behind the car to reduce drag, while at the same time the fast-moving air underneath the car will create a low-pressure are which will pull the car down.

[jagman]

How are they similar, a TRD wing is nothing like the o/e wing

Oh yeah - the trd is a 2 stage wing , with at least twice the area, and not bolted to the back with inverted winglets on the end.But using endplates and curved trailing edge- I m sure it must at least twice the lift as they got the original so wrong

[Smallshinyant]

ok sounds like a project. how do we go about measuring the downforce of wings? is it something that is possible by DIY means.

[Dnk]

A wind tunnel would be good or you could try Beast of Bomex's DIY route but im not keen on sticking bags of sand or cement on the back of my car

 

You could possibly work out an approximate figure for the TRD as its a known aerofoil shape in its x section that creates downforce due to the air flowing over it at differant speeds on its upper and lower surfaces creating differant pressures. Its also adjustable but not sure what the maximum angle it can get to is which will obviously alter the downforce by quite a bit.

 

No idea how you'd do the o/e wing as it curves away on its sides and in theory would lose downforce as the air can escape off the upper surface.

 

If you look at F1 wings they have end plates to help keep the air on the wing, same as they now have wing tips on planes

Edited July 6, 2010 by Dnk (see edit history)