do spoilers create drag?

[toph99]

my physics teacher and textbook say they reduce drag while increasing traction, i had always thought that they incresed downforce(traction) at the price of drag. he said that wind gets distorted at the end of the trunk area of a car, and the spoiler simply moved where that disturbance was to behind the car instead of on it. the example in the text book was a porsche 911. can anyone explain this a bit better to me? i'm confused

 

[LAUST]

Your conclusion is correct, it produces traction downfoce at the cost of drag... 98% of the things in this world come at the cost of something

My bad... your conclusion is for a Wing, whats found on cars like on Indy cars, a Wing will produce more RW downforce at the cost of drag. a spoiler is located closer to the body and is for making less drag and reduce underbody pressure that contribute's to lift also.

BTW they don't start working till about 150KMH+

 

[rootaxs]

Well, simply put. The way i see it, it works this way.

Since you are effectively increasing traction by pushing the rear-end of the car down closer to the ground you're putting your car in a more level field (e.g. parallel to the ground it's on) thus reducing the amount of drag (from an aerodynamic sense).

Exaggerating this a bit, think of your car with the rear-end "butting"-up (so to speak) on highspeed runs where the front is way low and the but is way high. That end that is sticking out will, instead of let the air flow through, will actually act as a parachute thus slowing you down (and thus drag)

Am i making sense?

 

[rootaxs]

Ok, off-topic from this topic.

Isn't that just dandy?

toph99 - Diamond member - Joined August 2000
LAUSE - Platinum member - Joined September 2000
rootaxs - Golden member - Joined October 2000

 

[Flat]

Spoilers can do different things... either produce downforce&drag, reduce drag/downforce or any of those combonations.

For example, think of a Volvo V70/850 wagon. It natural shape is a very high downforce creating design, the spoiler you so on the R and T5 versions reduces both downforce and drag for a higher top speed (which is about 162mph)

 

[mithrandir2001]

Doh! Streak broken.

Most dealer-installed spoilers do nothing for downforce...it's just rear-end jewelry.

 

[CocaCola5]

DOWNFORCE=Drag. Drag is preferred over aerodynamic disturbences as a result of (-)Downforce or LIFT. LIFT=CRASH at high speeds.

 

[hoihtah]

i have a mid level spoiler on my 97 integra gsr
if you ask me... it's not that noticeable.
i changed mine from stock to aftermarket one.
a bit higher.

but you'd have to be going pretty fast to realize the drag... i think.

but then again, what do i know

 

[Jzero]

<< Doh! Streak broken.

Most dealer-installed spoilers do nothing for downforce...it's just rear-end jewelry. >>



Tell it like it is, brotha. If it ain't shaped like a wing, it might as well be a sail. Yes, that monstrosity on the back of the honda you love to make fun of most likely actually slows it down.

Spoilers most definitely create drag, and at low speeds there probably isn't significant lift to outweigh the drag. However, at 200MPH, you get somre pretty phatty lift (yay bernoulli effect) and it outweighs the negative effects of the drag.

 

[toph99]

i'm going to have to discuss this again with my teacher on monday, this time i'll show him this thread thanks

 

[Superdoopercooper]

Dunno... but "Type-R" stickers definitely make your car go faster.

 

[Jzero]

Drag and downforce aren't necessarily the same thing. Downforce implies lift (downward lift) as a result of the bernoulli effect created by the inverse wing shape of the spoiler. Drag, OTOH is the wind resistance against your motion. If you put a plow on the front of your race car, it's going to make lots of drag but very little downforce....it's going to slow you down and nothing else.

Downforce converts drag to downward motion allowing the car to hug the road mo better. Drag can be used to help generate downforce. But not all drag is downforce.

 

[777joee]

Well said Jzero. It's all about speed!

And yes they do create drag and what you get is downforce, and downforce will give you traction with less weight which will give you more power to the drive wheels.



And on and on..........




Edit: If you want a good view of some early wings check out the early days of the Can/Am series and the Chapparel team cars form the early 60's. Pretty cool stuff.

 

[TurboQuattro]

A spoiler on a front wheel drive car is not a good idea, the driven wheels are in front, not in back. Besides, spoilers are only effective at speeds in excess of 130 or so MPH. Most of these POS cars you see on the road with them are not only FWD, they either don't have the power, or can barely reach that speed...It's a pathetisad and craptacular "look at me, my car is slow, but the spoiler makes it fast" mod.

 

[rootaxs]

<< And yes they do create drag and what you get is downforce, and downforce will give you traction with less weight which will give you more power to the drive wheels. >>



Hmm.. now i'm curious. Would you agree that front-wheel drive cars don't need that spoiler then? I may have this wrong, but isn't the spoiler there to help create downforce to the rear wheels = more traction = more power to drive wheels.

If so, should i put a spoiler on the hood? J/k hehehehe

 

[TurboQuattro]

<<

<< And yes they do create drag and what you get is downforce, and downforce will give you traction with less weight which will give you more power to the drive wheels. >>



Hmm.. now i'm curious. Would you agree that front-wheel drive cars don't need that spoiler then? I may have this wrong, but isn't the spoiler there to help create downforce to the rear wheels = more traction = more power to drive wheels.

If so, should i put a spoiler on the hood? J/k hehehehe >>



Exactly

 

[rootaxs]

Dop! hehehe.. just beat me to it

Anyway, i've effectively ran my car up to 145 mph on the track before i had to slow down, would be nice to see if i can actually make it to 160 on this baby. It's a FWD with a factory-installed spoiler. All bone-stock.




<< A spoiler on a front wheel drive car is not a good idea, the driven wheels are in front, not in back. Besides, spoilers are only effective at speeds in excess of 130 or so MPH. Most of these POS cars you see on the road with them are not only FWD, they either don't have the power, or can barely reach that speed...It's a pathetisad and craptacular "look at me, my car is slow, but the spoiler makes it fast" mod. >>

 

[StageLeft]

Yes they do. Especially ones that are designed properly; they increase drag while increasing handling so it's a trade off.

Drag and downforce aren't necessarily the same thing. Downforce implies lift (downward lift) as a result of the bernoulli effect created by the inverse wing shape of the spoiler. Drag, OTOH is the wind resistance against your motion. If you put a plow on the front of your race car, it's going to make lots of drag but very little downforce....it's going to slow you down and nothing else.

Downforce converts drag to downward motion allowing the car to hug the road mo better. Drag can be used to help generate downforce. But not all drag is downforce.

Seems reasonable. A properly constructed wing could theoretically give you downward lift with no significant drag. The sort of spoilers/wings (are we even talkinga bout the same thing? I think...) like on a porsche that pops up once you hit a certain speed is shaped quite simply and simply takes some of the windforce by pushing the car harder onto the road but also increases drag.

 

[CocaCola5]

Spoilers don't have to be over the driving wheel. This is a racing myth(perhaps from Formula One). The purpose of spoilers is to add stability not acceleration. Almost all cars, especially Hatch Back cars, suffer rear end lift, placing a spoiler at the rear, regardless if its a FWD, will help address this.

 

[TurboQuattro]

<< Dop! hehehe.. just beat me to it

Anyway, i've effectively ran my car up to 145 mph on the track before i had to slow down, would be nice to see if i can actually make it to 160 on this baby. It's a FWD with a factory-installed spoiler. All bone-stock.

>>



I've not been able to track test my car, but it's short gearing only allows a top speed of 149MPH, My car is not stock, it is chipped (ECU prom replaced to increase boost pressure among other things). A stock A4 is limited by the computer to 130MPH.

 

[toant103]

their cool looking

 

[Tominator]

A car moves through the air more efficiently if the air is directed around a car rather than under. Ground effect kits and front air dams attempt this, but you can only go so low on a street car. The front spoilers or wings on an open wheel car are there mainly to provide downforce. Some do have some effect on streamlining the tire, but that isn't the main purpose.

A rear wing or spoiler is supposed to smoothe out the air flow and decreae the vortex of air behind the car. They can also be used to provide downforce at high speed. The vortex creates drag. Reducing it reduces drag.

The purpose dictates the design. On street cars they add weight and nothing more. Some exceptions might be the very fast cars that go over 110mph or so.

A design that increases downforce and reducing drag is a trade off since increased traction equals increased friction and therefore it would increase non aerodynamic drag.

 

[Hellblast]

I have to add a thought to this from an aeronautical perspective.
The body of a car creates drag, no question. Now, this drag is produced because of the way the air flows around the body.
But then, the car stops!
The laminar airflow which has been maintained all along the car is destroyed when the car ends, so behind the car a lot of turbulence exists (example: open the middle-rear window on a pickup while carrying open leaves in the back).
One more: Turbulence creates drag, so reducing this turbulence by adding a spoiler (spoiling airflow at a predetermined point) will reduce drag.
My Point/Thought: It could be that the added drag from the spoiler is less significant than the REDUCTION of drag it produces behind the car.

Now, I also agree with anybody who said that it only comes into play at high speeds, which are normally not attained on roads in the US.

Hellblast

 

[TurboQuattro]

<< I have to add a thought to this from an aeronautical perspective.
The body of a car creates drag, no question. Now, this drag is produced because of the way the air flows around the body.
But then, the car stops!
The laminar airflow which has been maintained all along the car is destroyed when the car ends, so behind the car a lot of turbulence exists (example: open the middle-rear window on a pickup while carrying open leaves in the back).
One more: Turbulence creates drag, so reducing this turbulence by adding a spoiler (spoiling airflow at a predetermined point) will reduce drag.
My Point/Thought: It could be that the added drag from the spoiler is less significant than the REDUCTION of drag it produces behind the car.

Now, I also agree with anybody who said that it only comes into play at high speeds, which are normally not attained on roads in the US.

Hellblast >>



That sounds about right, I haven't thought about turbulence behind the car. I can see how that would aid high speed stability in a FWD car, but I think it would have to be well designed and wind tunnel tested.

 

[Cyberian]

Tominator -
I followed everything up to:


<< increased traction equals increased friction and therefore it would increase non aerodynamic drag.
>>


How does increased traction increase friction, and what is " non aerodynamic drag"?