Rear wing downforce?

[Mister_C]

Does the OEM wing actually create downforce? Or is it just asthetic? I know on most road going cars the rear wing is usually just for looks.

[red vtec]

I think I'm correct is saying that it does do something but above 80mph I seem to rember reading on here. I think it increase downforce and stability. The Sport 350 is the best wing for this due to its height. Rember Lotus are genuine sports cars not an everyday car with tacked on bits.

just found this link has all the info about Esprit wings

http://www.lotusespritworld.com/EGuides/EModifications/wingeffect.html

Edited December 13, 2009 by red vtec

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90% of all wings on road cars (actually it's probably nearer 99.9% but being conservative) are not wings at all but spoilers. These simply disrupt lift (and on aircraft generally do it with minimal drag) and on cars this is to counteract the natural tendancy for a car to gnerate lift from the basic shape of the roofline compared to the floor. As such a spoiler won't create downforce as such except by brute force redirection of the airflow which is not the most efficient. However they do have an important part to play and removing them does have negative effects to handling even though not true downforce.

A proper wing will actually produce it's own downward force independant of any lift disruption effect but quite difficult to get right. It's often easier and more athetically pleasing to build in lift surpression than downforce generation. For most cars it's difficult as the aero effect of a true wing relies on many variables that are subject to big changes that can make a cars handling change dramatically - it's why ferrari pretty much exclusively rely on underbody diffuser styling to get the required handling. It's much more predicatable and less susceptible to being upset by a change in the conditions than a proper wing (I also think ferrari prefer the styling of a wingless car). The S1 exige has twice the downforce of the S2 exige (100kg vs 50kg @ 100mph) and the s2 elise has considerbaly less than an s1. The S1 elise is well known to be a bit tricky on high speed corners because of this.

Secondly, wings generating downforce work best when acting directly over or through the axles of the car via somthing solid. Wings mounted to bodywork just don't work as well and again are more for cosmetic reasons. Just look at the Esprit 350 - proper wing not spoiler mounted through the bodywork directly to the rear subframe (IIRC).

Lastly, a majority of spoilers are situated too low such that any meaningful airflow is restricted by the passenger compartment and roof line rendering any major effect negligable. A big change to the Elise from S1 to S2 was to reduce the roof height and increase the relative height of the rear deck to make the rear bumper lip considerably more effective.

[matk]

Brian Angus stated at a prev Oxford meet that all the wings do something, but the main driving force in their design was asthetics.

[Günter]

mentioning issue 5/99 of *sport-auto* the S350 does have 39kg downforce (rear-end) on the known Daimler rolling road wind-tunnel ... . All on 200km/h , no reference given for the compensation of that on the front end.

Oh.. and just for interest: the F355 tested for the same documentary gives 42kg lift under same conditions... (but i can agree, it looks far more estaetic..)

[Advantage]

Secondly, wings generating downforce work best when acting directly over or through the axles of the car via somthing solid. Wings mounted to bodywork just don't work as well and again are more for cosmetic reasons. Just look at the Esprit 350 - proper wing not spoiler mounted through the bodywork directly to the rear subframe (IIRC).

The spolier on the 350 is mounted on the tailgate. Mind you, it's a relatively heavy piece of jewellery so perhaps that's what is pushing the back end of the car down - even when parked!

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Brian Angus stated at a prev Oxford meet that all the wings do something, but the main driving force in their design was asthetics.

Amything in the airflow will do something... the problem is if it's what you want or expect it to do ;-)

[Günter]

If you look closer into the evolution of the Le-Mans cars you can see that the same cars (our beloved Mc-Larren F1 for example) get longer undertray for this high speed track -and therefore more rear overhang over the years. It gives a longer lever on the rear end, and therefore you need not that much pressure on the wing to get the equal effect of downforce on the rear-wheels. What means if the undertray is as flat as possible, and as long as possible you have an stable flow of air under the car -and an more 'flat' shaped rear wing will not produce to much 'drag' behind the car ... .

So it would be important that the laws for roadcars just change, and allow an wider overhang of wings behind the rear lights

What do the specialists say, are my guesses right ?

[Bibs]

Getting air out from underneath a car is a priority, as it slows due to turbulence it creates drag and stacks and stacks of lift and the further back, the larger the effect. A flat undertray will help but by far the biggest reduction in this underbody lift is made by fitting a diffuser which accelerates the high pressure air under the rear of the car therefore reducing the pressure and associated lift as it's removed. That's why Ferrari love diffusers, does the job of a wing and then some without the added drag associated with a lump of anything in the airflow.

[Mister_C]

The rear spoiler on the Esprit does sit pretty high so I can see it being in the airflow. But that is one thing I wondered about. Even if it is creating some downforce it must also create a lot of drag at top end thus reducing it's top speed. I'm surprised they didn't introduce an underbody diffuser on the some of the last years of production with the Esprit being such a supercar and all. The new Elise has them.

[Bibs]

New Elise?

[Mister_C]

New Elise?

Sorry. The Elise currently in production. I know them as old and new haha.

[Günter]

Bibs, Ferrai does not only use 'diffusers' ..it's an whole system with the under-body from front end till the rear edge . That's what i meant with long undertray conception...

Ohhh, and for Colin: how's about the radiator in front? As the Esprit front end 'is sitting' on an big bubble of air (especially if you remove spare-wheel, CD changer and toolbox it is notable how light the front end is on high speed & uneven *Autobahn* sections). An rear underbody/diffuser would mean some risky 'levering effects' on the car i guess !? The top side of the Esprit nose does also have some notable low pressure/ lift section. Just drive in your car after you have not closed the front luggage-compartment. It will not come down on speed regions over 140km/h...

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Diffuser doesnt use a lever as such (and anyway that would create an upward force on the front wheels - it's one of the reasons you want any downforce acting directly through the wheels)

The long length of the diffuser is to get the air out the back and away from the rear turbulent area. Also lemans cars extended as a longer car is considerably more stable at high speeds.

The Elise diffuser is again more cosmetic - it needs to be considerably lower the ground to have any massive effect.

[arbell9]

We had a great wing/diffuser thread going a while back. While not the most scientific discussion on the topic it certainly added fog to the mist and trees to the forest.

CLICKY ME HERE for everything you didnt really want to know about wings but went ahead and asked anyway.