I need educating on Aerodynamics.....

I am running a stock spoiler in the front of my car and a rear spoiler that has a 5 inch rise in it. My car class in PCA-GGR TT's is "GM" which is any modified aircooled car up to 2750cc's. This class allows relatively free setting for airdams and wings. Many of the 911's and 914's I'm running against have larger wings and lower airdams.

My question: Is there performance to be gained by going to a different airdam/wing combo? I've seen skirts in the front that literally drag and wings on the back the same plane as the roof. I know my little wing in the back helps keep air from recirculating over the car and lifting the rear end...but I doubt in creates that much downforce....

I'm asking since as I continually tweak the car it usually involves knowledge, time, money, etc....which I rarely have at the same time...so I'm basically starting my education now.

Any thoughts or help in understanding would be greatly appreciated....

I've attached a pick of the car and it's current configuration....

Thanks,

Bill P.

A good place to look at aerodynamics is at: http://www.mulsannescorner.com/ where wings and spoiler are covered well. A couple of places that sell rear wings are Hoerr Racing and Sheridan Motorsports. From what I remember they are not cheap. I would try to find some other PCA racers that use them to see what they use and I can't help you there as the vintage organizations won't let us use them at all! Good luck.

Mulsanne's Corner For all your aerodynamic needs. I always wanted to play with aerodynamics for some self education.

I wanted to do stupid things like a huge front spitter that extends to behind the front axles. Making huge wings, and rear diffusers just to see what it would do.

Unless you have the hook ups at NASA, you probably won't be able to use their wind tunnel to play around. (something I would like to do)

I personally believe that more downforce will slow you down on the straight speeds, but may gain more traction for cornering so you can be faster in the corners. I think that lip wing does help keep the rear planted, but what about side to side movements? Wouldn't some endplates make a difference there? Kinda like an airplane, the tail wing (rudder?) keeps the plane from "spinning out".

Check this out: Loop hole to make larger wings.
http://www.mulsannescorner.com/audir8-01-6.html

hahaha! John Beat me to it!

Thanks guys for the lead...that site is pretty neat...I can pull out the engineering pad and start playing....

Alot of the risers on the cars look like one off's...a little fabricating may be involved....

ah...never ending....

Bill P.

Bill,

SCCA GT2 only allows a 6 inch rear spoiler similar to the one you have now.

If you do some searching... I think you will find that a SCCA GT2 9146 with a 2.9 liter engine turns faster lap times than ANY of the 914's running our PCA region with big mondo wings.

I totally LOVE the look... but until I can beat the times of a 2.9 liter powered 914 with NO wing (its a spoiler)... I dont feel I need one. We have one track in the state of Ca. where I think a wing helps out a lot... (Willow Springs) which is a very high speed track with high speed corners where downforce actually helps you get thru the corners.

The little 1.8 cars that Ron Wicker and Bontempi run... run 2:07's- 2:06's at Thill with NOTHING on the rear of the car (illegal for the class)

My .02

B

Thanks B,

I agree with you...I totally love the looks of the wings, but if I stick with my spoiler and can go faster...I'll leave it at that.

What about the front of the car? Do I need a knuckle dragging front spoiler? Or do I leave that one alone as well?

BTW, did you sell the tube car? I see references to it.....

I think you need a "splittler" for the front. This helps keep the nose down.

I have not sold the tube car. I was asked by one of my partnerts not to sell it... but that was before my wife lost her job last Friday.

We would have to go over what is available for the car... for a nice splitter/snow plow.

I know Chris Kolstad modified a readily available air dam and added a "lip" or splittler to it for 20$ or something.

I need a better pic of the front of your car to determine what it currently has.. these pics are a little too dark for me to see exactly what you have.

B

B,

Here's a pic of my wife at an auto-x. It shows the front spoiler...nothing special...yet

what's a splitter?....

And what size rims/tires are you running on your tube car?

thanks,

Bill P.

Here is a shot of my front spoiler with the splinter. The flat piece at the bottom edge.

It will make a huge difference the first time you drive it. You will feel it at the first turn. My splinter was fabricated from f/g, about 3/16" thick and under full heavy braking it is about 1/4 to 3/8" off the ground.

Paul

Brightened up the pic a bit to emphasize the front spoiler.