that is an awesome car, its like the ultimate 7 race car

 

Wow...thanks everyone for the replies. I knew there was more to it. I know you can't just tack on a couple of Lowes fans I also forgot (or maybe didn't realize) that fans cause air to swirl... As for powerstations and jet engines... WOW. Oh yes, and the sensors lol. Kinda forgot about those. K...I got it. It sure is very expensive...

 

K but I still want to know how I can get myself into one of those rooms....


:P That car's design is starting to grow on me, I used to say it was NSX>SUPRA>RX7 as far as JGTC models but I am starting to think differently....driving it in GT4 helped as well hehehehe...

 

besides the expense of the windtunnel itself, the gt300 class rx7 is a mighty fine machinery of what sex could be if it were a car.. btw those arent 19s, they gotta be bigger! cuz i have 19s.. =p

 

speaking of air pressure on cars isnt that kind of how lowering a car works? When you lower closer to the ground you cause a low pressure flow through the bottom of the car causing it to suck the car onto the raod? I take it that is why Ferraris and such cars are totally covered u on the bottom, for maximum down force is it not? I've been thinking about panellign out the bottom of the seve all the way back and finish it off with a defuser.

 

Great wind tunnel pics . Mm...they re-modeled the back rear fenders of the 7 . I wonder if it was for better aerodynamics or just to get rid of some extra drag ?

 

the SuperGT web site list the wheel and tire spec as 18x11 f/r and the tires are 280/710-18 f/r

I think the body work makes the wheels look bigger than they really are.

www.supergt.net

 

You have no clue on the innerworkings of a windtunnel. Back in the spring of 2003, i had the privelage of touring the Daimler Chrysler windtunnel in Auburn Hills, Michigan. to put the pictures in prespective, i'm the guy in the bright yellow shirt, and i'm 6'4.

 

thats a huge *** fan.

 

more pictures of the DC windtunnel

 

hell ya it is, they can take the wind up to 180+, but they won't go consistantly between 105 and 115, because 110 is where the fan blades hit their harmonic frequency

 

I think those fans are somewhere around 50,000 hp. In theory... very simple... But in reality...

 

I deal with fans all the time from a noise and vibration standpoint -- it is sometimes difficult to deal with a 72-inch fan and its 50-250 HP motor. I can't imagine trying to balance a fan that large, it's damn near incomprehensible to me....

 

I thought that was obvious from my post. No need to be an *** about it

Thanks for the pics btw...simply amazing.

 

Lowering a car simply lowers the center of gravity of the car. Now, if you're able to smooth-out the airflow under that car with pans that smooth-out the airflow (take a look under a Ferrari F430) then you will be able to accelerate the airflow and reduce pressure. It will help to have a splitter up front that would separate air flow, and a diffuser at the rear would complete the package (again, take a look at the back of an F430). With all that work done, the lower you are able to run the car relative to the road surface, the more efficient the it all becomes.

In the early days of ground effects, race cars would feature tunnels under the cars (imagine an elongated diffuser) that would really accelerate the airflow- the amount of downforce they generated was enormous. But the cars were incredibly sensitive to pitch, so engineers ran the cars with very stiff suspension setups for 2 reasons: 1-to maintain the angle of incidence of the underbody to the road, and 2- the downforce would compress the suspension.

When tunnels were outlawed in many sanctioning bodies, engineers discovered that a flat bottom chassis run in close proximity to the road surface would also generate downforce- not as much as the tunnels, but very meaningful amounts.

 

As in if the car leans to a side or to one end, the aerodynamics changed drastically? To the negative I suppose?

And the tunnels...were they banned specifically because of their sensitivity to pitch? What I'm understanding by tunnels are the loading ramps/tunnels you have that start a bit before the middle of the car, and enlarge as you go to the rear of the car, ending in an angled diffsuer? I thought many high-end cars go w/ such an undercarriage setup? (Vs. completely flat bottoms).

 

the wheels on the car sit on plates that have measuring devices that tell you drag coeffecients and other inportant info. thats the ture cost of a wind tunnel. its easy to make fans push air through a tunnel at high speeds. then you have to make the air smooth and direct it in a certain way. much more mathmatics in there than you can believe.

 

I skipped most of this thread but here is the facts

an airplane creates lift by slowing the air above the wing and the air below moves faster creating lift but if you eliminate the air underneath the wing and have a curve that the air above the wing pushes up against then you get downforce.

A wind tunnel is expensive to build because of all the fans and MEASURING EQUIPMENT that everyone seems to forget a windtunnel has tons of electrical **** that measures every little bit of airflow that the object inside changes. Now all this technology is very expensive therefore the price of the wind tunnel goes up.

Both of these things I learned in my 9th grade tech class years ago when we built co2 powered drag cars. also my dad is a pilot.

 

No, those are NOT "the facts."

Lift on an airfoil (aircraft wing) is created because the air flowing on top has a longer distance to travel, and therefore travels at a FASTER speed relative to the air underneath. This creates a low-pressure area on top of the wing, and a high-pressure area underneath the wing. The pressure gradient exerts an upward force on the wing. We call this "lift"

A similar principle exists when dealing with a car's wing (only upside down from a standard airfoil)


I'm an engineer in the Air Force and deal with a lot of this stuff regularly. Most of the wind tunnels that we use are much smaller than those used in the auto industry (for those who don't know, the same principles that apply to full-size vehicles also apply to scale models). It's much easier to build a scale aircraft and fit it in a test chamber than find one big enough for a full-size. Even these small test chambers are extremely expensive due to the precise construction, and extremely expensive measuring devices.

However, we also have a few large test chambers that would absolutely dwarf the one at Diamler-Chrysler. Those things are just amazing to see. I used one for some work on an F-15, and it took us about 2-weeks just to set up all the measuring equipment (the tests were performed in less than 2 days, then it took another few months to download and analyze all the data).

-Rob

 

Tunnels were banned because cornering speeds became way too high.

Pitch sensitivity was a result of acceleration, braking and cornering forces loading the chassis and changing the aerodynamic center of pressure on the car, and the handling characteristics of the car. For example, if you lifted the throttle at speed, the resulting forward weight shift would change the center of pressure, and the rear would lose grip- not the sort of thing you want to deal with at speed.

More recently, engineers (where possible) would dump the exhaust into the diffuser or tunnel to increase air speed (for example, a 3.0 liter F1 motor turning 17,000 rpm moves a bunch of air). Same problem here, too. Lift throttle changed the performance of the diffuser, and balancing was a delicate act. These days, F1 cars have their exhaust vent above the bodywork to help induce air to the rear wing.

Fun stuff.

 

gcthree, def. fun and interesting stuff. So the best design now is a front splitter, a complete full-length sealed and FLAT undertray, ending in a diffuser in the rear, right?

 

I was contemplating designing a flat panel bottom for the 7, but there are a few problems with this idea..... the most two most important being cooling for the transmission and exhaust vents for the radiator fans. I guess you could make a hole in the undertray to let air flow past the cooling fins on the tranny, anyone care to comment on this?

 

Dan, the tranny has cooling fins?!

 

I guess the casting you see under the tranny, that looks like grids, acts as cooling fins.
More surface area, draws heat away, faster heat dissipation.

I was playing around with some undertray designs for the Cwest bumper a while back.
And have the same question about covering the whole underside of the car...

jupiter

 

There are lots of facts, and not facts in this thread about the aerodynamic priciples expaining downforce for the wing on this awesome 7.

Rob, the AF engineer, whom I personally know to be a good guy, and is not only knowleageable in his field of engineering, but also in the workings of a rotary engine, explained in textbook manner the most common priciple, the pro Bernoulli, or air foil theory.

I said theory, because amazingly, this is not fully proven. Recently, there is another theory of lift based primarily on Newton's third law, (for every action there is an equal and oposite reaction). You can actually see in the picture the air being deflected up away from the wing, thus pushing down on the wing, and creating downforce.

In the end, it is likely a combination of both these priciples.

Although I am not an engineer, (I'm just a general surgeon), I was also in the AF because of my love for aviation. Too bad that love did not coincide with my field of expertice which also did not coincide with military thinking. I'll be glad to discuss that in private with anyone thinkng about a military career.

Anyways, that car is totally awesome!!

Galo