But what about that 437 pound load distributed over the width of the wing? It may flex a bit but it probably won't snap. Remember, it's carbon fiber - 3X the strength of steel at 1/10th the weight.

Who knows though, you may be right.

 

The weight is not pressing down *edit* solely *edit* on the wing, it is pressing down on the car in the area under the wing... And besides, as someone else earlier mentioned, downforce is not mass, so it cannot be equated with putting the same amount of mass on the wing. It is simply a way to measure an equivalent number in relative figures. Think about it - F1 cars can produce over 3000 pounds (1500kgs) of downforce at speed. Why doesn't the car break apart?

 

 

You don't need a program to get rough estimates. He extrapolated the new downforce numbers by multiplying the original downforce by the square of the ratio of the new speed to the old speed.

 

BTW, I don't think the downforce will be that high. At least not net downforce. Keep in mind that as speed increases, underbody lift does, as well. This is why I mentioned in my original post that the Evo's wing doesn't really provide pavement-sucking downforce in the sense that most people think. It merely negates the lift in the rear end, not that this is a bad thing. To generate true downforce (and in this application, it would upset the car's balance), there would have to be some type of diffuser tray under the rear (similar to the front). Before someone does this, consider that if you have smooth airflow at the front, and then smooth out the airflow at the back, you'll end up with a pressure area in the center of the car. This is why many sports racers have full flat-bottom or venturi-bottomed cars - to eliminate any pressure areas and have smooth underbody flow. Ideally, we would have someone construct us a panel that would attach to the rear of the front panel, travel the length of the car between the wheels and mate up to a panel at the rear to diffuse the airflow cleanly out the back. If we had that, then any canards (at the front) and wings (at the back) would have true aero effect at high speeds (not just negating lift). Hope this helps...

Chris

 

Complex topic & one on which I have absolutely no expertise, so I will jump right in.

First, the wing is shaped like an upside down airplane wing (flat on top, curved on bottom, thick in front, thin in back). So, given that airplanes defy gravity every day, it is logical to assume the EVO's upside down wing does produce downforce, especailly at 85 mph, when most planes start to get airborn.

Also, in the rain at the track, my EVO has abosutely killed the rear wheel drive fast cars from 95-125 mph. While the rear of 'Vettes, etc., kept stepping out sideways, the EVO stayed totally planted. I am sure all wheel drive helped, but I think the wing was a factor also.

 

omg u did not just write that

 

**stupidity edited by SC and user thread banned**

If you don't have anything constructive to add to a thread, please don't post at all.

 

The numbers I gave are valid so long as the downforce is actually 70 lbs at 60 mph which someone else thought they read. Once a downforce is known at one speed, it can easily be calculated at another speed.

Downforce = .5 x ro x A x (V^2) x Cl

ro = air density

A = frontal area

V^2 = velocity squared

Cl =coefficient of lift

The only varible above that changes is velocity so basically once a downforce is known for a given speed, the equation can be simplified:

Downforce = K x V^2 where K is a constant.

If the actual number at 60 mph was actually 35 lbs, then 150 mph would = 219 lbs of downforce.

I'll do a little digging through some text books and see if I can come up with an esimate for Cl.

 

Here's a relevant quote from http://www.autoweek.com/cat_content...._code=05031754.

 

I tried to put it into terms that would be easily understood. I guess I failed. Bottom line - the wing is functional, but only to negate lift.

 

Think of this upside down (but keep in mind the disruption of airflow coming from the trailing edge of the roof):

 

Here is part two (also upside down):

 

The primary difference between our wing and an aircraft wing in this discussion (besides its orientation) is that an aircraft wing has only air above and below the wing surface. Our wing has the body of the car under the wing surface in addition to air. This is why I stated what I did earlier. This is also the reason those little CF "fences" you can get (from Monster, I think) are there to deflect the air rushing under the wing. Keep your mockery to yourself until you show me something that refutes this. I couldn't find a diagram of aero on a vehicle, but I have pics here at home (no scanner, sorry).

Here's something else (kinda long and about Mustangs, but you'll get the idea):

http://realbig.com/detomaso/1997-06/336.html

 

This isn't an airplane wing. It's a "spoiler".

The shape of the rear window and deck would result in a low pressure area over the rear deck at high speed, creating lift on the rear end. (This body shell did start life as an econobox.) The spoiler disrupts this lift, keeping the rear weight on the ground. It's not adding down-force so much as removing lift.

As for it being "ineffective" below 85, it does interact with wind at much lower speeds: FWIW: When I park my EVO facing downwind, and have 20 mph of wind coming from behind, the wing (with the wind flowing backwards over it), produces enough lift to throw open the trunk as soon as I pop the catch.

I haven't had a chance, yet, to park facing upwind, to see how much wind it takes for the wing to push down the trunk enough to latch the catch on its own.

The forward flowing lift that the spoiler negates may be insignificant below 85 mph (forward air speed), but the wing interacts with wind to some degree at any speed.

So when operating the trunk in a windy environment, ... "let's be careful out there".