Aerodynamics

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Zamani
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Aerodynamics

Post by Zamani » Fri Dec 24, 2004 1:44 am

OK this topic is seldom discussed. There's a track out here in California which is very fast and it's possible to hit 120-125 on the straights. My 75 has euro bumpers (like the normal 1.8ie) and the bigger skirts. What will a lower lip/splitter or a slightly bigger wing (like the IMSA cars)?
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Post by Seb » Sun Dec 26, 2004 11:51 pm

Zamani!

My track car is a 75 (3.0) aswell. Great track car IMHO. The aerodynamics is one of it´s weak sides though. Getting a car to be fast in the straights is the hardest to I think. Less down force and so on... My "home track" is fast in the straights aswell, and 200km/h (120-125mph) is not impossible.

I´m not sure one or a few splitters will make a difference. For some effect I think a lot of things have to be combined. Take a look at the race 75`s that was run in the 90`s . Thar might give You some ideas. on what to do.

Interesting thread, I hope we get som good comments. Allways looking to make the track car faster. :D

Btw, where in Cali do you live? I used to live in LA, Santa Monica.

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Post by 81GTV6 » Mon Dec 27, 2004 6:39 am

Some serious GTV6 aero dynamics.


My two cents is it cant hurt to have a more aerodynamic car. Plus its alot scarier to be up against a car that looks fast, as opposted to one that looks stock.


I want mine to look like this monster!!!! :twisted:
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Post by Micke » Mon Dec 27, 2004 2:36 pm

Small changes - minimal benefit!!

Do you want more speed on the straights or downforce in curves?

The only thing you can do to improve both is to make a flat bottom to the car.
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Post by Barry » Tue Dec 28, 2004 12:05 am

Agree totally with Micke,
Also Keep the air from going under the car in the first place if you can.Hence the ground scraping ,full surround front spiolers.If you cannot do the frnt. spoiler ,at least deflect the air around the car as much as possibleLittle deflectors under the floor pan ahead of the rear wheels does wonders for stability as well.As Micke says,cover the rear suspension and streamline it as much as you can.You have all these pipes and tubes an stuff realy cousing serious drag with all the air clinging to everything.

A double bonus is stopping the engine compartment air from going under the car.You wont stop it totaly,but by extracting most of it from the bonnet or hood helps this as well as ,if done properly, the under hood cooling and radiator cooling.Remember ,the frnt 3rd of most hoods have a negative pressure acting on them and the last 2/3rds have a positive pressure acting on it.So ,ectract the underhood air ,dont fit vents and louvres to the rear ,this will force air into to bay.

Lower the car as much as proctical.A smaller space beneath the frnt spoiler =less air under the car.Although a sh&t load of air enters from the sides.Give the car some rake,ie.the frnt lower than the rear-about 3 to 5 deg.

What were taliking about here is nowt unless the actual car has also been streamlined-Raingutters ,protruding mirrors,lamps,appendiges etc.

We built a 105 gtj for the 1/4 mile a few years back and all the rain gutters etc was removed to aid the times-To this day I could not tell you if any of this worked,but I do remember it was a load of work.

A major point to look at is the "PARACHUTE "AT THE REAR OF THE CAR.iN MY OPINION THE SINGLE BIGGEST EARODYNAMIC IMPROVEMENT YOU CAN MAKE IS TO EITHER REMOVE THE REAR -DAMN,SORRY ABOUT THE CAPS-bumper complete or at least cut the lower center section out and fit some mesh into it so that the underside air can be exracted.

Z,This is a bloody good subject--Where is Jim K??And mats etc?Brian?

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Post by Dennis » Tue Dec 28, 2004 1:30 am

Good pointers there Barry! The problem with a flat bottom is our rear suspension (and exhaust, but you can take care of that). If you look at the EVO set for the 75 you'll see exactly what Barry is stating. Low sideskirts and a massive front bumper with a splitter. Nevertheless, it would be a great project and you could definitely benefit from these mods. Why don't we start collecting pics from racecars to discuss what would or wouldn't work with our cars? I'll kick off with a URL because there is a lot to see:

http://62.58.172.77/challenge/opbouw200 ... ListPage=1

Especially the IMSA lookalikes are interesting!

Mind you that tinkering with aerodynamics can be dangerous if you don't know what you're doing! I was at the Ferrari museum a month ago and had the opportunity to take a look under the F360 CS and 575 GT racer. These have a very simple looking flat floor and diffuser, but these guys know what they're doing and have their own windtunnel :shock:
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Post by Seb » Tue Dec 28, 2004 1:33 am

Great written Barry, thanks!

Does anyone have any pics of how home made solutions of a Venturi tunnel might be made? Maybe some other of Barrys tips?
How to "streamline" the rear suspension?


I´m in the middle of doing these mods to my car (75 3.0) , very good timing starting this thread Zamani :P


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Post by Seb » Tue Dec 28, 2004 1:35 am

And thanx Dennis for a great URL!!

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Post by Mats » Tue Dec 28, 2004 3:57 am

I'm lurching... :wink:

It's just such a difficult area and the more I read about it the more I realize just how much time and effort needs to be pourd into it to get it to work.
Downforce is great, maybe, if the car is set up for it. You need a really well handling car before adding aero and the aero stuff needs to be balanced as well. Now, how the f**k does one measure downforce? Linear sensors and a logging program? How many of us have access to that?
Ass sensor? :) Probably better but is it accurate? Anyone heard of the Placebo effect? :wink:

What happens if we add a flat underside?

1. Exhaust? Either we cut a hole/slot for the exhaust or we will have serious temp issues (I'm talking F1 heat inside the car and a glowing exhaust tip thet will set fire to anything...

2. Trans cooling? Pump and heat exchanger needed. I see 130 degrees in my tranny after a few laps and that is in my 140Hp car with fully exposed tranny. The oil will not like much higher temps then that.

3. Brakes? They need to be moved outboard, period. exhaust and tranny and brakes in the same area, yeah, right...

Now you probably think I'm really negative as usual but I'm just trying to point out that in order to make a working aero-pack the whole car needs to be designed with that in mind, very few add-ons work wothout drawbacks. Rear lip or wing is probably the only one.
Front spoiler adds a whole different environment under the hood and needs to be very thought out and tested to work well without removing cooling for brakes and engine (including all sub-sustems).

I recommend anyone interested to read:
Joseph Katz, "Race Car Aerodynamics: Designing for Speed (Engineering and Performance)" ISBN: 0837601428
and of course Carroll Smiths books. :wink:

By the way, we need a certain air flow under the car to make use of our flat underside. No air flow - no downforce.
Look at the Mercs flipping at Le Mans a couple of years ago, they flipped because they bottomed out and the front lip touched the ground stopping the air from going under it -> loss of downforce -> flip into trees...
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Post by 4SFED4 » Tue Dec 28, 2004 5:17 am

This is great tavern talk... not sure how practical though. Whilst it would be great fun to take these experiments to the wind tunnel (Barry and Mats make some excellent points), I don't see the opportunity to do that in the near or distant future. Shall we give Ron Dennis or Jean Todt a call... pardon me lads... might we borrow your wind tunnel for the day? Me and me mates would like to improve the aero on our 30 year old bricks! (lol)

To whomever posed this question orginally... put your time, effort and cash in to some professional driving lessons. You will make a FAR greater impact on your track times than any aero improvements.

-Brian
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Post by Seb » Tue Dec 28, 2004 5:23 am

Hmmm... I migth build a Venturi tunnel anyway, just because it would look cool and MIGHT work! :D Anyway try to make an easier way out for the air in the back.

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Post by Dennis » Tue Dec 28, 2004 5:29 am

Well Zamani first asked about the benefits of a splitter and then Barry went berserk with ground effects :lol: We'd better call Peter Sauber. He's just built the best windtunnel in Europe! Also never underestimate the power of thinking your car is faster :D

The EVO kit offers quite a bit better aerodynamics then standard, so that should help in improving downforce/less drag!
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Post by SamW » Tue Dec 28, 2004 7:30 am

A few months back there was an article in the US Alfa Owners club magazine about some who was racing an Alfetta and built a scale model and used a small university wind tunnel to test the design, then mocked it up to his race car, it looked pretty good. Maybe someone who has the article can post it here for us.
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Post by P.Webb » Tue Dec 28, 2004 8:01 am

SamW wrote:A few months back there was an article in the US Alfa Owners club magazine about some who was racing an Alfetta and built a scale model and used a small university wind tunnel to test the design, then mocked it up to his race car, it looked pretty good. Maybe someone who has the article can post it here for us.
That's Mike Cudahy from Wisconsin. SCCA E-Production Alfetta.

The article is NLA on the AROC-USA website. I'll ask him if he has any info I could share on it. I'll be at his shop installing an MSnEDIS on that car in the next month or so.

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Post by Seb » Tue Dec 28, 2004 8:06 am

Please do Peter!

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