Just a little more info… the “spoiler” on Champ/Indy cars aren’t the only bit of the equation of the downforce. They are incredibly complex aerodynamic machines, with pretty much every part modelled for some benefit.
On a street car, they have basically no appreciable value unless the car is designed for one, is going very fast, and they are large enough… and yes, just a rear spoiler would put a lot of downforce towards the rear of the vehicle, which you need to counter with weight in the front.
I’ve taken my old '84 Mercedes 190E (with no spoiler) up to the 130 range (er, no mention of where), and that is right about where I started getting really uncomfortable with it. A spoiler on it probably wouldn’t have done much good, but I was basically running into a wall of air at that point anyway. The aerodynamics of the car wouldn’t allow for much more, with or without one, even with the poor engine straining as hard as it could. A Saturn wouldn’t even enter into it
Other parts of the car are equally vital (in addition to the under/overflow mentioned above)… namely, the tires and suspension system, airflow into the engine, etc.
NASCAR vehicles are different with their weight distribution… namely, they have a bigass engine up front, whereas Champ/Indy cars have the engine back behind the driver… kinda necessary to have the big downforce generated by the front wings with the 800 horsepower being kicked out the rear end. I’m sure you’ve seen what happens at drag races when the tree hits green, or when a champ car gets a wheel off the ground at high speed. They do.
Sure it does. It is an upside down airplane wing (as my cite from CART mentioned). Additionally, though they are technically wings, they tend to have (especially on superspeedways) a bit of a spoiler on the trailing end of the rear wing. The effect is that the wind suddenly hits it and pushes against and thus down.
As mentioned, they run a different configuration on superspeedways. These days, they use the Hanford Device, which is a happy fun thing (for the audience, the drivers loathe it for the dangerous situations it creates) that hangs down from the rear wing and creates a lot of drag, slowing the speeds down (the good part. Back in the '80s and early '90s, drivers were pushing over 250 in speed tests, which is just dangerous)… this has the side effect of creating a huge air pocket behind the car… the ideal config for a champ car would be to slip through the air without leaving so much as a hint that the car was there, because leaving a big hole behind you means that when someone is there, they don’t have to cut through the air and can get a significant speed boost (or just conserve fuel). This results in much closer and more “exciting” racing (the bad part, except for the fans, who love it. This is why NASCAR is so popular. Unfortunately, with open wheeled cars, being close and passing a lot is VERY dangerous). There were races in the late ‘90s with 50-60 lead changes during the race, which is friggin’ insane. Often, the race would “come down to” the last lap, when 4 drivers would be neck and neck swapping the lead in each turn. In reality, it was happenstance for whoever happened to be in second (or sometimes third) place coming out of turn four. They would “slingshot” around the leader coming onto the straight, and the poor chap would drop right back to fourth place without a chance in the world. It looked exciting, though. The drivers also complained that it minimalized their piloting skills, which has some truth to it. The ideal race for a driver is one where he can make clean passes and run at a safe distance from the competition, with his position based on his skill in cornering, choosing his lines, and sometimes pit strategy.
Um, crap, there’s that off-topic thing again. Anyway, all of that wraps back around to how the aerodynamics work, I guess.
That’s not true. There is a tremendous amount of drag on the car at those speeds. Most cars are power limited probably in the 120 mph region. But 140 requires quite a bit - a Subaru WRX will go 143 MPH, but it’s 3000 lbs and has 227 horsepower. A Subaru WRX STi has 300 HP, and can hit 155-160. It takes 73 extra horsepower to get an additional 15 MPH, because drag forces do not increase linearly with speed, but exponentially. So while many cars can hit 120-125, very few can make it over 140.
So people are making fun of a minivan with a spoiler, which I agree would look ridiculous trying to make a minivan for “The Fast and the Furious”, but wouldn’t a spoiler be more beneficial for a minivan/SUV than it would for a Saturn?
As I understand it the spoiler is creating turbulence behind the vehicle to offset the effects of drag. This is the same concept as a smooth sphere not being as aerodynamic as a golf ball, where the dimples are creating turbulence along the trailing portion of the ball. Given the size of the back of the minivan/SUV, wouldn’t you want to try to have less drag?
WAG…with a car, the size of the area to be disrupted is less and easier to negate the effects of the entire area, whereas a minivan will be extremely difficult to make enough turbulence compared to the area of drag to make a difference?
In addition to any other drubbings this statement will cause, you can also kiss the accuracy of your speedometer goodbye as you get over 100. The read out is definitely on the high end, and gets progessively worse the faster you go.
If the gearing is ‘right’ you can squeeze a few more MPH than some stock gear ratios, but y’aint gonna turn a 115 mph car into a 140 MPH car.
The A-Team van had a spoiler, and they were tough.
Don’t me makin’ fun of my spoiler, chump. I pity the fool that makes fun of my spoiler. Grrrr.
(Any chance the spoiler actually cleans up the air behind the car, and contributes to reduced drag from dirty air, which equals some economy benefits. And, Porshe 911’s can hit 160+, but their spoiler pops up at 50 or so.)
My 94 Saturn SL has been up to almost 220km/h (like 218kp/h or 135.5 m.p.h)
I wouldn’t recommend doing that often, but it has been done, and when the highways have been deserted I have been known to go 170kph (about 105mph) for longish stretches… It may not get there as quickly as a Ferrari Maranello…(anyone want me to test that just gie me the keys ) but it does reach high speeds without much of a problem…
You’re basically right about the effect, but the spoiler isn’t there to create turbulence.
A turbulent boundary layer is much more energetic (more mixing of high-speed fluid) and resists separation in adverse pressure gradients much longer than a laminar boundary layer would. That’s why they put dimples on golf balls. The dimples trip the boundary layer at the leading edge and the BL stays attached further around the body, resulting in a smaller wake and lower drag.
On a car, you’ve already got a turbulent boundary layer at any reasonable speed due to speed, rough attachment line, and all the other crap on the car that trips it. The spoiler is there to keep the wake flow from feeding forward through this boundary layer and causing early separation. On a generic car body, the boundary layer might separate over the rear window, but if you add a spoiler, you can prevent this separation and keep the wake behind the spoiler.
Note that this does not apply to the wings on a Saturn since they have a space underneath them and won’t keep the wake pressure from feeding forward.
