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Discussion Starter · #1 ·
I have been running my rear wing on full tilt. This increases rear grip, but radically decreases top speed as it increases drag. Over 60/70mph, in a straight line, the car is alot slower than people would think (negating some of the power increase!!)

I am thinking of trying it straight again on the track, but was curious if anyone could provide some scientific answers as to what the benefits/disadvantages are of the wing positioning in its 3 positions, to save me the trial and error effort!

Good info would be CD drag coefficient with the spoiler in it's various positions, as well as how much downforce the wing produces in it's various positions.

Is there another way to improve rear downforce without increasing drag (underbody)??
 
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Discussion Starter · #2 ·
In my experience I would say get the front of the car as low as possible,adjust the ride height at the track,this will reduce lift.You can add a front splitter DTM style get PE to make you one.Keep the wing at standard position but add a gurny on the trailing edge .Fabricate a panel to cover the prop and exhaust this will again reduce the lift and create ground affect,you should then have the ultimate track car .Run suspension as stiff as possible in the dry ,with 4deg of camber at the front.Rework arches to take 10x18 wheels at the rear and 9x18 at the front.and make sure everything is fully rosejointed.

Let me know when its ready,Best wishes Barry:)PS.If you want the ultimate handling track car take it to a company that prepares race cars,
 
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Discussion Starter · #3 ·
Blade

This gets a bit difficult. Before we can begin to calculate drag and lift for the wing, we would need to know details on the section being used and the different angles produced by the 3 settings. It would be possible to load the offsets of the wing into a simulation programme to get the figures, but I am not sure whether all this is worth the hassle. I would suspect that 2 things could improve the wing. I doubt it is using the optimum section and wonder what the rally boys are using (grp a) Secondly, finer adjustment would also help. F1 cars adjust 1 degree at a time.

The issue of downforce against drag will vary depending on track. Lift goes up by the square of the speed, so on tracks with slow corners and long staights, set it on minimum wing. On other tracks it is a case of trial and error but if there are high speed corners and if the straights are short, go for max wing. The longer the staights, the more the need for finding the best compromise.

I read somewhere that the wing on the 7 produces 14kgs of downforce at 100mph. It did not state in what position!

If I can help further, please let me know. A mate designs wings for British Aerospace and he can be a great source of info.
 
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Discussion Starter · #4 ·
Tony

do a search. I've already stated some facts concerning the downforce of the rearwing measured by SportAuto.

Cheers

Mike
 
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All I remember you saying about the rear spoiler is that is produces 12kg downforce at 200 kmh (or flat out, cant remember). Which doesnt mean much to me (does it to you?). In max down position that is. :p
 
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Discussion Starter · #6 ·
The place that I read the figures for the 7 wing suggested that it was more efficient than the 6. However, the laws of aerodynamics still apply.

So if the 6 produces 12kgs of downforce at 200 km/h, at 100 km/h it would produce 3.46 kgs of downforce. However, whilst the wing will increase drag due to its own form factor, there might be a compensating reduction in drag because it tidies up the rear airflow.
 
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Discussion Starter · #7 ·
Blade

I have also been thinking about how else you can get better aerodynamics. Your comment on the underbody made me think. Fitting panels to give a smooth underbody would help, but I cannot quantify it. However, I am not sure how expensive it would be and it might not cost a great deal to find out. Only issue I can identify is that it might effect cooling to gearbox, diffs etc. As for potential to create a low pressure zone at the rear of the car, I would like to believe that it was possible, but I am sure there are better ways of increasing speed around the track that are more proven.
 
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Discussion Starter · #8 ·
There are underbody protective kevlar panels available. Although designed to protect the sump etc., they may also be an effective aerodynamic aid.

I am considering the large GT wings available from Japan (like that fitted to the HKS Kansai and JUN EVOs) - ugly, yes, put possibly more functional. There are also splitters available, though perhaps the TME front bumper is more effective than the standard GSR one ????
 
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Discussion Starter · #9 ·
One thing Evo's really don't need in my opinion is more rear grip unless front grip is increased dramatically.
 
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Discussion Starter · #10 ·
Blade,

there's some really good (though generic) info on aerodynamics in C21 Performance book. Basically this says that if you are going to run alot of down force at the rear you need a similar amount at the front or you will upset the balance of the car too much. The way to get downforce at the front is with a splitter. On a road car this is not really practical as you would lose it at the first sleeping policeman. However on your beast it would certainly be worth considering.

The optimum would be to have a system that can be lowered/raised as appropriate which is what i beleive is on some Skylines but dunno for sure.

An underbody diffuser (twin venturi shaped) would also be worth considering as this would generate a low pressure area under the car sucking it onto the road, but to get it right you could spend (another) fortune plus there's the cooling consideration (mainly around the gear boxes and diffs).

Keep us all posted on this as its great to see what can be done with an Evo in terms of ultimate development.
 
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Discussion Starter · #11 ·
I wouls like someone to explain what 12 kg or 3,46 kg of downforce means in terms or cornering speed increase. These figures on their own are pretty worthless.
 
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Discussion Starter · #12 ·
Clauidus, my understanding is that the more downforce you produce, the more you are stuck to the ground, so the more grip you have and the faster you can go. Cars tend to produce lift the faster they go, making them light at the front and the rear too, increasing the chance of spinning on fast corners. Problem is, downforce alone can increase aerodynamic drag, meaning you waste power trying to cut through the air (the car effectively acting as a brake). if you can increase downforce, and reduce drag, you can get the most out of the power of the car, and grip, and so go even faster!

Interestingly, I am running 3 degrees of camber at the front, and 2 degrees at the rear at the moment. Won't go to 4 degrees without at least a splitter. Am thinking the TME bumper is a better design aerodynamically, so may get one of those. I have found someone who can make the under panels in carbon, but need someone to design it for me (anyone know any university automotive students interested in a project???)
 
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Discussion Starter · #13 ·
Claudius,

Good question. On the face of it 12kg is #### all. This equates to about 15 litres of fuel or less than 1% of total vehicle weight. F1 cars run so much downforce that they could drive upside down in a tunnel. You'd probably get more downforce if you turn your sub up high:).


Whatever its worth investigating the splitter as it will probably improve drag coef because it will stop some of the air going under the car.
 
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Discussion Starter · #14 ·
12kg of downforce is actually quite a lot considering that it is the net downforce it generates. The total downforce the wing generates is 12kg |PLS| the lift the car generates.
 
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Discussion Starter · #15 ·
We've discussed this already several times but..

If the downforce of the rear wing was useless why did they bother with one? And even changing the design from Evolution to Evolution. As Michael said it gets rid of the lift and additionally creates downforce.
Just check Tommi's car during this season. They used different settings on different rallies.
I'm also certain that the Makinen Version front bumper gives better aerodynamics and downforce compared to the standard one. Otherwise again they wouldn't have bothered with it. And even easier just look at it as the bumper is formed like a splitter.
On the Ring which is very fast it made a noticable difference between full downforce and low down force mode. With full downforce it's like having a parachute attached at 180km/h but in the faster corners it feels more planted.
The secret is to find the downforce without adding too much drag. That's what Adrian Newey is very good at.
The F1 cars create (in Monte Carlo configuration) so much downforce that they could drive upside down from 160km/h on. This is also a reason why they're still that fast in the wet. For a F1 the zone between 80-160km/h is most dangerous for aquaplaning above the aerodynamic presses the car on the tarmac and below it's not an issue.
I would be very careful by adding under panels. Do it wrong and you've create lift. To get downforce and less drag this would need a wind tunnel with a rolling floor to reproduce the state of driving and then testing different configurations. Not cheap. Sauber is currrently building one for 50 Mio. CHF (20 Mio GBP)

Cheers

Mike
 
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Blade

I know what downforce means, I was just wondering if the rear spoiler is set to full down, how much faster can you go thru one particular curve as a consequence? Like 100 kmh instead of 95 or 105? You know...

Hey, Rallytech make carbon fiber front bumpers, I think the TME version as well. You can buy the underbody panel from Japan or else my local rallye team make them, do you want me to ask them how much they are? I think they use them for protection on gravel.
The complete Rallytech price list is on http://www.myevo.com
 
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Discussion Starter · #18 ·
Many good ideas here and I have been thinking of what else would improve aerodynamics. A custom front spoiler, much lower to the ground, with a fence to reduce spillage underneath, would be of benefit. But if you are not concerned about racing regulations, then the obvious thing is to have an electrically variable rear wing. Button on the steering wheel, press button at beginning of straight, less wing. At the end of the straight, press button as braking commences would achieve 2 things. Increases drag to help braking effort and increased downforce for the corner.

In addition, I was thinking about my old BMW 3.0 CSL. The aerodynamic package included bonnet fences, 20mm high, mounted on the edge of the front wings. This helps reduce turbulence caused by airflow slipping around the wings and A posts. Then on the back edge of the roof, there was a hoop like spoiler to help the airflow stay attached around the back of the car and reduce the turbulence that the rear wing operated in. On an Evo, I suspect this last feature would add to the effectiveness of the rear wing, increased downforce and maybe even slightly reduced drag.
 
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Discussion Starter · #19 ·
Blade,
If you are looking at fitting underbody panels to your car for an improvement in downforce and not for protection of the sump etc (as used in rallying) then the best method is to create an underbody shape similar to the top surface of an aeroplane wing. This creates a venturi effect that accelerates the air flowing under the car and this in turn reduces the pressure under the car creating more downforce. This will probably be harder to achieve than varying the rear wing but it will provide a greater increase in downforce without the added drag (which is a good thing :))
This is how cars such as the Mclaren F1 and Ferrari 360 manage to get good stability at high speed without using big wings etc.. and it was also used to great effect in the older formula 1 cars until it was banned because they were cornering too fast.

The other way to increase this effect is by getting the front of the car as low as possible (as mentioned by others above) so that you reduce the airflow under the car. If the splitter is low enough, you could use this as a good start point for fitting the underbody panels from to create the wing shape.
I wouldn't fancy driving over any sleeping policeman with it on but as a trackday car it would be unbeatable.

Hope this helps

Andy
 
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Discussion Starter · #20 ·
I think it's pretty pointless and possibly dangerous to add on aerodynamic parts to a car without at least a professional simulation program trying the aerodynamic effects at all possible speeds. I'm quite sure nobody on this board knows how the Evo performs aerodynamically enough to be able to engineer parts for it. It ain't as easy as I'll stick a spoiler on here, a panel under there...hmmm, that should do the trick , even if it looks like a good idea we don't know how the air behaves around that part and how it influences the air for other parts of the car. Basically the only really safe way to do it is if you have at least all the relevant data for the airflow and to be sure, a windtunnel. And a full underbody could be even more dangerous cause it'll reduce the cooling of f.e. the diff. and other parts and wouldn't want to know what that could do... How about a rear diff. seizure at 100mph??
 
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