Touring Car Downforce

[rcr286]

I have been involved in an ongoing debate at work about the amount of downforce a touring car (particularly SEAT) can generate. There is also confusion about the difference between the ETCC SEAT and the SEAT Leon Super Cup.

Someone threw out a figure of 200kg @ 150mph, but that seems ridiculously high. I was under the impression that the touring cars were limited. I also find it hard to believe the Supercup car would produce these figures; even though it has a very nice underbody and diffuser, the high wing would not really aid in the diffuser's ability to produce a significant amount of DF.

Does anyone have any real world figures to help out here?

Thank you

[Sodemo]

With regard to actual figures I do not know. However all road cars produce downforce at high speeds, modern car design and the general profile of the bonnet and windscreen generate downforce on all road cars, how much I do not know, a few KG?

[rcr286]

Actually, most road cars produce lift, and high speeds only exacerbates it. Look for SportAuto Super Test scans online and you will find that even the best cars produce lift. You will also find that manufacturer claims (i.e. Ferrari) are crazy exaggerated.

I stated that this is a "debate at work", but we are actually trying to use our bull-shyte-o'meters to sort through manufacturer claims for a project I am working on.

If you have information, it will benefit many...

[stedevil]

Originally Posted by rcr286

Actually, most road cars produce lift, and high speeds only exacerbates it.

Makes sense to me. After all a smooth curved upper side is exactly what makes an airplane wing produce lift. OTOH, the smooth curved top side and lower pressure on the tires would help with fuel economy, so I guess this is mostly a bad thing for performance cars meant to be driving at high speeds where fuel economy is less relevant.

[Sodemo]

That certainly is news to me if true.

Cars produce lift?

[JMeissner]

Indeed they do.

[Speed-King]

Originally Posted by Sodemo

That certainly is news to me if true.

Cars produce lift?

Even racecars did until the late 60s. I seem to remember a story about the original style Porsche 917 (or was it 908??) that had quite the issues with lift.

[wheadon]

so did the miura

[BertMk2]

Audi claim their DTM car can do the "drive on the ceiling" thing as it can generate enough downforce to do so (at about 150mph I think was the figure given). But I guess DTM cars produce way more downforce than an S2000 car.

[Aslak Vind]

Former F1 driver Kiesa commented after racing Audi R11, that it had F1 like downforcelevels.

[rcr286]

Anyone else have data on the S2000 Touring Cars?

[rob21]

I think your figure is ok.
If you know software LapSim from Bosch,there is front drive touring car example with some aero specification and if I remember in this simulation software downforce level is just over 100kg@200kph so around 150kg@150mph.

[chunder]

I would imagine that the downforce applied to a saloon is not specifically designed to glue the whole car down, more an "end"

The issue always was getting heat into rear tyres, front grip was often combatted by serious diff tech, I remember reading a test of the Primera Aiello car and Hales was amazed by the diff tech involved.

Rear grip was probably helped by spoilers and not sure now if this is still an issue, I would guess so.

I know that the Alfa was a very slippery shape, and the SEAT a good car to draft!!

[SEATFreak]

I am sure the front-wing of an F1 car is what creates the air-flow underneath the car which, at such high speeds creates enough pressure (??) to stick the car to the road. So, if is it local to assume, and without doing the research, the front splitter on a touring car does the same job?

[rcr286]

Thanks Rob21. I have heard of the Bosch program before, but for some reason never found it. I am installing as I write this.

Do you have much experience with this program? Do you think the data is pretty legit, or is it just a place holder?

Does anyone else have some input on this?

Thanks again

[rob21]

Originally Posted by rcr286

Thanks Rob21. I have heard of the Bosch program before, but for some reason never found it. I am installing as I write this.

Do you have much experience with this program? Do you think the data is pretty legit, or is it just a place holder?

Does anyone else have some input on this?

Thanks again

I have a little bit experience with this software.I have only demo so there are only some basic simulations to play with. It looks like those physics files are realistic.There are also some others cars specifications and looks like to me ok .

[Martin Haven]

Originally Posted by SEATFreak

I am sure the front-wing of an F1 car is what creates the air-flow underneath the car which, at such high speeds creates enough pressure (??) to stick the car to the road. So, if is it local to assume, and without doing the research, the front splitter on a touring car does the same job?

the job of the front wing on a single-seater is to channel the air, both above and below the car... it is the relative difference below low-pressure and high-pressure areas on cars that generate lift, as in 'planes...

for an aeroplane to fly, the wing has to generate "positive" lift (lift in an upwards direction), so the upper surface of the wing is longer than the lower surface... as the air-flow tries to remain laminar (imagine parallel lines of air molecules), the air molecules must move faster over the top surface than they do over the bottom surface... this generates a low pressure area above the wing (same amount of air, but spread thinner, if you like) and the wing moves upwards, pushes by the high pressure towards the low pressure...

this much has been known (and then understood) by aviation types since the early 1900s

now, some bright sparks decided this could be applied to cars - but in reverse... turn a wing profile upside-down, to generate "negative" lift (or 'down-force', as it became known, to help simple folks distinguish between lift [up] and lift [down]) and instead of taking off, a car would be pushed down into the road surface, helping the tyres grip at crucial junctures... like in fast corners and under braking...

in essence, a single-seater (and here we must also include the likes of Le Mans prototypes, among others) aims to create the low-pressure area UNDER the wing (and here we include front and rear wings and the whole body surface) instead of on top of it...

the wings and all those other god-awful aero add-ons on an F1 car are largely needed to direct air-flow where it's needed, to avoid creating drag (the enemy of speed) while still generating significant downforce...

wings are also used to alter the balance of the car, by adding or losing downforce at one end or the other

Colin Chapman's major step-forward with 'Ground-Effect' wing cars essentially featured an enclosed tunnel alongside the tub with upturned wing profile inside to literally create a low-downforce area, as the underside of the side-pod was longer than the flat top surface... this only worked if the 'tunnel' was sealed effectively, stopping normal-pressure air rushing into the low-pressure-area (nature abhors a vacuum!) hence the sliding skirts to seal the car to the road... when skirts stuck (or cars jumped kerbs) and air leaked IN, cars flew off the road alarmingly, as they were only successfully cornering so fast because of the aerodynamic effect and when that was lost, the car was simply committed at a far higher speed than the tyres would cope with... ouch!

To return (briefly) to topic, touring car airdams usually serve to tidy up the airflow, ensure under-car airflow is within tolerances (ie no actual lift - as mentioned, this was a major flaw in the early 917s and the Muira - among many others) by using a splitter to channel as much as possible OVER the car, and as the route over the upper surface of the car is longer than the route straight underneath it, generate the desired low-pressure area underneath

of course, when you have 300bhp and not 900, you have to be very careful as regards creating drag, so too much downforce is not a good thing

the n-technology Alfas were mentioned and Thommo confirmed their major advantage was their ultra-low-drag configuration...

in fact, when he won both races at Valencia in 2007 with the car, he trimmed the rear wing off so much that he was developing positive lift on the straights... it makes the car 'lighter' as it's partly 'flying', helping the engine move it faster down the straights... plus, it picks up a 'tow' better and gives a worse tow to those behind...

anyhow, this doesn't help with real numbers... but if I remember I will email someone and try to get a 'soft' ball-park number...

[rcr286]

Hey Martin, I just looked you up and am sure that you have some solid connections within the European racing circles. If you could come up with some real numbers that would be great. This is actually for work and not just some "watering hole" debate.

As an aside, I have just bookmarked your Dakar blog. We do not get coverage in the U.S. and have been passing around recorded videos of daily coverage. Between the videos and your blog, we should be covered.

Thank you

[Jacob Black]

for Dakar coverage, also see www.sbs.com.au/dakar it has daily videos etc.

[Martin Haven]

Originally Posted by rcr286

Hey Martin, I just looked you up and am sure that you have some solid connections within the European racing circles. If you could come up with some real numbers that would be great. This is actually for work and not just some "watering hole" debate.

As an aside, I have just bookmarked your Dakar blog. We do not get coverage in the U.S. and have been passing around recorded videos of daily coverage. Between the videos and your blog, we should be covered.

Thank you

Afraid that the blog was written in 2007! I am not on this year's Dakar... doing bobsleigh instead!

Will try and get some numbers - naturally, no-one wants to reveal actual numbers to any degree of accuracy but I will see what I can get

[stedevil]

Originally Posted by Martin Haven

doing bobsleigh instead!

What happened, you slept with the boss' wife?

[rcr286]

Yeah, I realized the 2007 date just after I posted.

I understand playing it close to their chest, as unfortunately I have to do the same, but if you could get someone to confirm the 150 - 200kg @ 150mph and give 'approximate' percentages up or down from there that would help a lot.

Go ahead and email this to me if tit would be easier to convince someone to share some info.

[S14GJC]

Originally Posted by Sodemo

That certainly is news to me if true.

Cars produce lift?

Yes, the first generation Audi TT did, hence it has to have that little wing on the back of it.

They were re-called in before fitting them on production.

[dynamix]

This was a study done by a russian mag i believe comparing the evo with impreza.

Shows distinct lift for the evo at both ends at two different speeds (sorry I dont know what they were) and front end lift for the impreza.