300bhp/ton said:
This is exactly WHY you don't get it.
OK, we'll see who doesn't get it. Ready??? See below
***.
300bhp/ton said:
Outside the US - where lets face it all competative rally cars hail from. Roads are not just STRAIGHT,we make use of the steering wheel and yes we do drift the car round bends.
Well, golly gee Mr. Limey you must know everything. All roads in the US are completely straight. No curves or bends. All turns are perfect 90* right angles, straight as can be. Get a clue
You guys drift
STREET CARS???????????????? Come on now, who doesn't get it??????? This whole discussion started about STREET CARS. STREET CARS DO NOT PERFORM MANEUVERS THAT WOULD REQUIRE STABILIZERS (IE DRIFTING OR JUMPING)!!!!!!!! Even if they did STABILIZERS CREATE DRAG TOO!
300bhp/ton said:
Also you admit that the wing does act as a stabilizer - well surly thats a FUNCTION is it not.
Yep, but not a function a street car can use. The whole WRC thing was thrown in to show proof that the street car surely had a functional wing because the WRC team had one. Again, a rudder function or air brake function are not properties associated with a "wing". If you think it is then a rear view mirror mounted to a door could be considered a "wing", so could the door if you open it while driving the car. please, keep grasping.
*** To calculate a vehicles drag (Cd) you use the following formula:
D = Cx*q*A
D = aerodynamic drag force in lbs
Cx = coefficient of draq
A = automobile frontal area in square feet (ft**2)
q = dynamic pressure in lbs/ft**2
Note- drag is directly proportional to both frontal area and Cx and proportional to
velocity squared. Therefore, if you double your speed, you will quadruple drag.
Now, you might be saying "But gp, you said the wing created drag and this only uses frontal are to calculate drag". Well, this assumes the flow over the body stays attached (no spoiler on the rear decklid). Since the STi's wing i mounted directly to the trunk lid (no vertical slats elevating the upper wing surface) the bottom of the wing creates a spoiler.
Take a look at the air flow in the pic of the Mercedes in a post above. Imagine a small vertical spoiler on the decklid and how that would affect the flow lines going over the car. The airflow hitting the spolier would shoot up into the flow above, and thus drag is created.
Now let's move on to the wing itself: does it create useable downforce, or just drag?
First off, for a wing to generate any form of down force it must be in clean air. This would mean it needs to be higher than the roofline of a sedan (and therefore would affect the drag formula above by increasing frontal area). Look at the picture of the 69 Dodge Daytona posted earlier. The wing is higher than the roofline, and that is why it was functional. To keep the flow attached over the body the Dodge engineers made the rear window flush with the pillars (Daytona and Charger 500). But since the STi wing (as with most production car wings) is mounted lower than the roofline it's not in clean air and is not producing downforce. So, we know it is not producing downforce as part of the fow over the car, so what about on it's own? Let's investigate.
I hope you would agree that wings in their purest design are devices to produce lift (downforce or negative lift in cars). But a direct by product of generating downforce/lift is the production of drag. But this amount of drag is only one component. The wing itself generates profile drag (this would be the drag produced in a neutral state - ie zero lift). So, how do we calculate this drag? Well, it's called Induced Drag and it is proportional to the square of the lift or downforce created
Cdi = Cl**2/(pi*e*AR)
Cdi = induced drag coefficient
Cl = coefficient of lift
AR = aspect ratio of wing (wing span squared/wing area)
pi = mathematical constant (approximately 3.14159)
e = wing efficiency factor
So, we know that the STi wing creates drag (both at the mounting base and the profile of the top) and little downforce (if any) based on the physics above. We also know that drag varies with the square of speed. we also know that the power required to fight drag varies with the cube of speed.
What does all thie mean? Well it means:
By someone who gets it said:
The wing on the Sti is in no way functional. Unless, of course, you consider generating more parasitic drag (which is the biggest force to overcome with speed, ie it eats the most horsepower) functional
By someone who gets it said:
Anything extended upward into the airflow generated drag. Most of a car's horsepower is used trying to overcome drag.
By someone who gets it said:
Yes reduction of aero lift and downforce are not the same ON A RACECAR, but since we are talking street cars that will never see enough speed and a good enough aero package to overcome their bulk the WING people are claiming is functional must be used to counter lift (you certainly don't believe a 300hp street car weighing 3000+ lbs would need more downforce for anything other than to counter lift, do you?).
And my favorite
By someone who gets it said:
A wing on a street car is a useful as this thread*
*edited for clarity