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thetunersgroup
22-09-10, 04:23 PM
http://www.tunersgroup.com/images/large/large2112.jpg

Hi All,

Given the amount of serious aerodynamics seen on a number of the top cars at the 2010 World Time Attack Challenge, and our work with cars we sponsor like Mark Berry's Yokohama Advan R34 GT-R, we have had many enquiries lately from people asking us about how they can improve their car's aerodynamics, and how aerodynamic improvements can improve their lap times.

Accordingly over the last few weeks we have put together one of our biggest tech articles ever ... an introduction to racecar aerodynamics, particularly in regards to time attack racing, and how aero can improve your lap times.

You can find the article here ...

http://www.tunersgroup.com/engineering/aero_intro.html

- Adam

zappy65
22-09-10, 04:43 PM
Good read, thanks Adam.

saad
22-09-10, 04:59 PM
Awesome article. I want a wing now

Can you explain how a wing helps FWD cars though - it seems to work, but not sure why or how?

*bj*
22-09-10, 06:42 PM
My rear spoiler is made of rubber.

Do I win at downforce?

(P.S. good article!)

thetunersgroup
22-09-10, 07:36 PM
Awesome article. I want a wing now

Can you explain how a wing helps FWD cars though - it seems to work, but not sure why or how?

Hi saad,

I have put together a simple explanation on the front wheel drive situation, but rather than post it as a reply here on the forum I'll get one of our aero experts to expand on the front wheel drive info and will add the front wheel drive info to a new section in the article.

Thanks for asking the front wheel drive question - it's an important question so we'll address that in the article.

- Adam

thetunersgroup
22-09-10, 07:41 PM
My rear spoiler is made of rubber.

Do I win at downforce?

(P.S. good article!)

Hi Blake,

Flexible materials like rubber are actually sometimes used in aero parts, particularly in the past.

On the factory rear wing on a Porsche 930 for example, Porsche used a slightly flexible rubber-like / plastic material around the outside and back of the wing, on a solid tailbase ...

http://farm4.static.flickr.com/3505/3743875062_c4fa12e26d.jpg

It is only slightly flexible, so it doesn't lose shape at speed, but the rubber-like material is relatively heavy when compared to carbon fibre.

- Adam

uknowsergio
22-09-10, 08:04 PM
Great article Adam, looking forward to the data you have stored and your help with my build!

- claudio

DrewMan
22-09-10, 08:45 PM
I always thought that a larger wing for FWD car was detrimental since by pushing down on the rear tyres, it would lift the front ones and provide less traction?

thetunersgroup
23-09-10, 04:16 PM
I always thought that a larger wing for FWD car was detrimental since by pushing down on the rear tyres, it would lift the front ones and provide less traction?

I've just added the following to the main article ...

Some people claim on various internet forums that a rear wing is of no use on a front wheel drive car, but that is not correct.

It's important to remember on a front wheel drive car that though the front wheels are the driven wheels and simultaneously put power to the ground as well as steering, the cornering load is shared between the front wheels and the rear wheels.

So it is possible to increase the rear grip by adding rear downforce, which can potentially help cornering speeds.

However, whenever adding downforce to a car, it is very important to get the balance of front downforce and rear downforce right.

Under braking the weight balance of the car that the tyres see tends to shift to the front wheels of course, so additional rear downforce can have an effect on how much grip the rear wheels have under braking.

The majority of the braking is done by the front wheels of course, but when you bear in mind that all four wheels can provide braking force, if you can increase the rear grip without reducing the front grip it is possible to increase the overall grip under braking of the car as a whole.

If a car is running an aftermarket front splitter for example without a rear wing, the addition of a rear wing can then produce downforce at the rear, helping to address the front downforce to rear downforce balance, but that balance requires you to look at front downforce and rear downforce simultaneously of course.


The Importance Of Balancing Front And Rear Downforce

It is also very important to balance the front and rear downforce, because if a car has significantly more downforce at the rear than at the front, or has lift at the front, the front of the car can feel light under certain situations on the track.

That lightness in the front of the car can lead to understeer, simply because the front wheels are lacking grip relative to rear grip. If you've ever towed a trailer with a front wheel drive car, you'll be familiar with how the additional weight of the trailer on the rear wheels relative to the weight on the front wheels can influence the front grip and handling.

So in many cases whether the car is rear wheel drive, four wheel drive or front wheel drive, adding a rear wing should also include adding downforce at the front of the car to keep the front to rear downforce balanced.

http://www.tunersgroup.com/images/large/large858.jpg

As an example of adding front and rear aero simultaneously, when Porsche developed the rear ducktail spoiler for the Carrera RS they also added a modified front spoiler / bumper assembly.

There is a very interesting diagram in a book about the Carrera RS where the car was tested without both spoilers, with only the front spoiler, with only the rear spoiler, and with both the front and rear spoiler.

Using the car with front and rear spoilers removed as the baseline, the results were:

- Front and rear spoilers removed: baseline
- With rear spoiler only: speed increased by 0.5 km/h over baseline
- With front spoiler only: speed increased by 2 km/h over baseline
- With front and rear spoilers fitted: speed increased by 4.5 km/h over baseline

So with both spoilers fitted, the speed increased.

Generally speaking, a lot depends on if a car has balanced front and rear downforce before a wing is added, or if the car has more front downforce than rear downforce before a rear wing is added.

If a car is already making front downforce but not generating enough rear downforce (or generating rear lift), then the addition of a rear wing can balance the front and rear downforce numbers.

Just like on a rear wheel drive car or four wheel drive car, on a front wheel drive car if you can increase the grip available to the tyres by adding downforce, without adding excessive drag, you can potentialy improve laptimes.

The key of course is to get the balance of front downforce and rear downforce correct.

As it says in the article ...


adding downforce adds effective weight to the contact patches where your tyres meet the track, (ie the weight your tyre's contact patches "see") thereby potentially creating additional tyre grip.

So on many track cars where you are trying to increase downforce, what you are trying to achieve is an increase in front downforce and an increase in rear downforce, while keeping the balance of front downforce to rear downforce correct to avoid introducing any undesirable handling or grip issues by getting that balance wrong.

- Adam