downforce? please read

What's the difference between downforce and weight? I understand that spoilers create downforce on your vehicle, but how is that different from putting weights on your car? Couldn't you just slap heavy sandbags on to your car and get the same results as a spoiler?

Please reply!

basically yeah. Spoliers and such are placed in locations that are beneficial to the car's handling and getting power to the pavement. All they do is force (for example) the rear of the car down at higher speeds so it is more stable and the tires stay down on the road better. Basically, you could do the same thing with sand bags i suppose but you would increase the overall weight of your car defeating the purpose. Those wings dont really do anything though that you see on imports and regular cars. You have to be going hella fast to get much downforce.

ya, pretty much the only cars that do are f-1, funnycars, etc. the ones that go about 180mph

basically yeah. Spoliers and such are placed in locations that are beneficial to the car's handling and getting power to the pavement. All they do is force (for example) the rear of the car down at higher speeds so it is more stable and the tires stay down on the road better. Basically, you could do the same thing with sand bags i suppose but you would increase the overall weight of your car defeating the purpose. Those wings dont really do anything though that you see on imports and regular cars. You have to be going hella fast to get much downforce.

So weights would produce more traction than a spoiler at low speeds? Than why has nobody tried to do that in autocross or rally? Stress on the suspension or something?

So weights would produce more traction than a spoiler at low speeds? Than why has nobody tried to do that in autocross or rally? Stress on the suspension or something?

because the weight produce more weight. when a car is heavier, it accelerates slower and is more difficult to handle, you want a lighter car when you race.

Oh, I see, so the momentum of the car would make the extra mass harder to accellerate and deaccelerate, wheras the spoiler would decrease and increase the amount of downforce depending on the speed? Thanks.

The other thing about weight is that it shifts, downforce just pushes down a car according to it's shape giving more grip to the tires are high speeds

All I got to say is...

If your cat does not have 300+ HP

a spoiler is kinda useless...

If u have 110 Hp on your honda and u got a spoiler... ::Cough:: Ricer! ::Cough::

Who the hell are u kidding?

U really think u are going to get downforce at 30 miles per hour?

No... downforce begins at least at 120 MPH for it to actually kick in.

Otherwise it's just useless.

So you're saying if i had a 300hp civic, I should strap on a spoiler? I don' think so. Its the fact that civics are FWD that makes spoilers almost useless, of course there are a few exceptions, but I'm just saying in general.

Additionally though, you don't need 300+ Hp to do 120mph. So i think you're kind of contradicting yourself.

Okay, quick physics lesson 101

E = MV

Energy = Mass x Velocity

Therefore you need to use more energy to get a heavier mass to the same speed than a lighter mass. Therefore, for a given amount of engine power, a lighter car will accelerate faster all other things being equal. It will also brake faster and be more nimble. It won't work its brakes as hard nor will use as much fuel... weight also got this property of inertia. If you instance stuck a pile of ballast in the rear bumper then yes it would help your initial traction but in a high speed lane change you could end with it acting like a pendulum and flinging the car into a spin (don't laugh ask any 911 or original Beetle owner what the pendulum effect is in a rear engine car).

And to be honest, I know a lot of rear-engine rally car drivers who put bags of cement over their rear axles to aid traction in years past.

Now that assumes all things remain equal - which they don't.

Mechanical grip is the relationship your tires have with the road surface. The more grip you have - the better you are able to take the energy of the engine and use it create motion - lest you end up wheelspinning. Which to some looks spectacular and is the stuff of pubescent boys wet dreams but is basically wasted power. If you have better grip then traction allows you to use more throttle off the line and accelerate better.

Grip is another double edged sword - wider tires give better grip but induce more drag. Adding weight increases initial mechanical group but you pay in the extra energy once initial traction difficulties are overcome and grip becomes less crucial to acceleration.

When it comes to cornering, you tend to want to have more grip the faster you go.

Aero aids add a relatively small amount of weight but add a fair bit of extra mechanical grip once a certain speed is reached. This again is compromised by the additional drag of the aids. Also during acceleration in a straight line - grip is less of an issue and at high speed aero aids can limit top speed. On the other hand, aero aids can add stability (witness the retro fit of the boot spoiler to Audi TTs after high speed stability issues).

Now 'downforce' can be achieved a number of ways. You can stick to a big spoiler which adds a lot of drag and depending on your suspension setting will compress your springs more than adding downforce. Or you can stick a big front splitter to reduce 'lift' or use a sloping aero underbody with venturis to reduce drag and produce downforce.

Some folk will tell you that 'downforce' doesn't happen to super high speeds... now that's true but reducing lift and improving stability can happen at relatively low speeds (and reducing drag too)... and the aids can be quite subtle...

The main issue with wings on imports etc are they are crap. For their size they don't actually produce much effect and are usually for styling purposes. If you look on the trailing surface of the trunk of a current BMW M5 you'll see a subtle kick in the surface. That very subtle and discreet little spoiler actually has a significant effect on the high speed stability.

Trouble with a lot of the wings for road speeds is that if you went down to the library and got manuals on NACA profiles for the speed range you'd end up with something that would look quarter of a oil drum with slotted holes drilled 3/4s of the way up with end plates. Doesn't look very nice at all and not a lot like the wings you see with less transition that are used in race cars - and would produce a lot of drag at higher speeds.

You could go for an aero aid with moveable surfaces but you add weight and complexity.

Trust me buy wider tires, upgrade springs and shocks and get more power!

"No... downforce begins at least at 120 MPH for it to actually kick in."

PROVE IT. Back your claim up. You're full of it and i can back my claim.

It's odd that I had a 110HP Neon that could do 120MPH A spoiler wasn't necessary at all. It sure as hell needed a splitter in the front, but no wing.

spoilers can work at highway speeds, it doesnt matter if you have fwd, it will still be effective. most cars that come with spoilers from the factory do work, you dont have to go over 100 mph for it work. lots of car companies have done tests to see how spoilers effect a cars stability at highway speeds, and found it to be quite effective, there were noticeable differences.

Also don't confuse the spoiler and the wing, the differences have been discussed in this forum several times before.

"No... downforce begins at least at 120 MPH for it to actually kick in."

PROVE IT. Back your claim up. You're full of it and i can back my claim.

It's odd that I had a 110HP Neon that could do 120MPH A spoiler wasn't necessary at all. It sure as hell needed a splitter in the front, but no wing.


I agree, if they think it has to be high speed, they should stick their head out the window at 50 k's, plus the spoiler/wing (I dunno the difference) has a larger surface area than your head so think how the spoiler would be effected....



I also agree it is quite useless on a FWD car, I just can't find a reason how it would be better to have a bigger tendency to lift up the front end...

the problem here is that i think most people who buy a wing are drag racing far more than they are road racing. for drag racing the wings are kind useless unless you are breaking 100mph by the end of the 1/4 mile, they are just producing drag. if your drag racing only get a spoiler (if you have a fwd car) if you feel your car getting all squirly by the end.

now if you are doing more road racing and are concerned with handling then you might want to get a wing (even in a fwd car cause you may set up your suspension to oversteer).

i dont have time right now

spoilers work on front wheel drive cars too. at higher speeds, the rear end tends to lift, so a spoiler will help it stay planted to the road better. it doesnt matter if the rear wheels arent being driven, the rear wheels are still there providing grip, keeping the rear end stable.

Spoilers work on any drivetrain configuration cars (or well-designed spoilers do) because their purpose is not to create downforce but to "clean up" the air behind the car.

Wings work on any drivetrain configuration cars because, as CrzyMR2T said, it does not matter which wheels are driven, it's still benefitial to have as much grip in the corners in a race. Road racers, in BTCC for example, will not bolt anything on their cars unless it's functional, and most of the cars there are FWD and all of them have wings.

what's the difference between a wing and a spoiler?
I read on a site that a spoiler is that thing you put on your front bumper and on your sides (sideskirts). and a wing is that thing sticking out back.

http://autozine.kyul.net/technical_school/aero/tech_aero.htm

A spoiler is much smaller and usually has little or no air passing underneath it. It also sts lower on the car and most of the airflow towards it is blocked by the car body in front of it. A wing is something that sits higher so that the airflow towards it is not disturbed by the car body and it gets plenty of "clean" air for maximum effect. As I said, their purposes are not the same as the wing produces, or should produce :), downforce. The aim of the spoiler is to direct the air behind the car so that the car moves through the air most efficiently with less air vortexes behind it.

This is a good picture where you can see both a wing and a spoiler (the part protruding backwards from the roof) on the same FWD race car.

http://motorsport.honda.de/images/galerie/btcc_800.jpg

and another of the same car

http://www.davebrockman.pwp.blueyonder.co.uk/btcc/generics/drivers/2003chilton.jpg

There are also front spoilers (and splitters) that are used to direct air around and, when that's beneficial, under the car.

And an example of a spoiler on a sedan. As you can see, the airflow towards it is almost blocked by the car body

http://www.spoilersmax.co.uk/Spoilers/peugeot_306_spoiler_sedan.jpg

Wing on a sedan. As you can see, it's much higher and the roof does not prevent the air from getting to it and under it, otherwise it would not be effective.

http://dspace.dial.pipex.com/mg.maestro/btcc/mediaday/mediaday2.jpg

So if not much air goes through the spoiler of the peugeot, then wouldn't that be kinda pointless?

A wing puts more downforce in the back, correct?

BTW, what are air vortexes?

Vortexes are whirling streams of air. The spoiler is pointless at producing downforce anyway, that is not its function.

Ales, the only exception to that was if you were running a tunnel floor or diffuser floor car. The front splitter prevents the air going underneath the car and by having expanding channels and side skirts, you can achieve downforce by ground effect. The relatively dense air gets to occupy a steadily expanding volume which results in the ambient air pressure under the car being less than ambient air above the car.

The diffusers create the expanding volume and allow the rapid egress of the air to the back of the car to help with reducing the drag vorticies behind the car too.

I wonder why they banned ground effect in F1...

Safety reasons. The cornering speeds had become ridiculous. Also if the car lost the ground effect downforce for whatever reason the result was almost certainly a violent crash.

You can lose ground effect downforce as easily as a wing can't you?
Ground effect is pretty much creating lower and lower pressure under the rear of the car right?

Safety reasons?! IMO, I think there should be less safety equipment on those cars so that there is less weight and the sport would be more extreme. Maybe I am crazy, but that's what I think.

You can lose ground effect downforce as easily as a wing can't you?

No.
As the term implies "ground effect" relies on the cars close procismity to the ground for it to work. The ground underneath the car is actualy used to help create the low pressure air flow.
If for any reason the car is lifted even an inch to far from the ground (as can happen if you run over a curb, or get touched by another car, or a tyre skips as it skids etc) the ground effect is lost very violently as air flowing around the side of the car is suddenly allowed underneath it where it rushs into the area of low pressure.

What's the difference between downforce and weight? I understand that spoilers create downforce on your vehicle, but how is that different from putting weights on your car? Couldn't you just slap heavy sandbags on to your car and get the same results as a spoiler?

Please reply!

getting back to the original.....

both terms result in perhaps more road grip, which is primatively given as Weight*tire contact surface or Mass*gravity*tire contact surface

however, sandbags increase the mass (or weight, depends on how you wanna look at it, but since gravity is pretty much a constant on this planet (only differing in california with all the airheads) think in terms of weight when visualizing, mass then using a formula or two) ALWAYS, meaning when you goto corner, the result will be unfavorable, when you goto accelerate the result will be unfavorable, when you goto brake, ditto.

now in terms of wings/spoilers, they can be used for the SAME purpose, even tho they have cross purposes. with respect to aerodynamics, a car has to do 3 things with air:

1) ingest a relatively small amount to run the motor [1]

2) move a larger amount out of the way

3) put that larger amount back.

the spoiler helps put it back differently, but does not do near a good a job as someone drafting you ;-)

since a wing is an inverted airfoil like those used on a dragster or IRL car, the 'car side' is the low pressure side meaning airflow speed is increased which improves laminar flow across the body. this in itself would lend to less overall drag and high speeds, cept for that low pressure side of the wing (the top in this case) which greatly increases drag, but also downforce.

so lets visualize how the air flows around a car with none, some or all aids...

no aids at all: the front end punches a big hole. creating small low pressure areas a little rearward of the part of the car that punched the hole. concentrating ONLY on the top of the car, the shape of the nose and rake of the glass create both high and low pressure areas over the hood/glass. older cars with a more blunt nose and steeper glass had a high pressure area down where the wipers parked (hence the fresh air intake for the HVAC and sometimes a reverse hood scoop was used there) this is not very areodynamic, todays cars have universally a longer slope blended with the front, and with the curved windshield create 2 low pressure bleed areas off to the side that extend down the front doors (go look at where your car is filthy after a drive at speed in a rainstorm) these bleed areas fill in the larger low pressure and turbulent areas on the sides of the car.

now consider the air flowing over the roof, the reverse rake of the rear glass now creates a void resulting in a low pressure area over the trunk area - this does not HELP rear downforce. Recall if you will in the heady days of the late 70's and mid 80's when chevy made 'aerocoupe' versions of first the caprice then monte carlo to satisfy nascar rules so they could be run in competition. these cars moved the low pressure area to the rear more to wheret he boundarys started to merge with the biggun located right behind the car (and this biggun is the one that literally holds the car back)

now consider same car, but add the spoiler. Not all of the air coming off the roof misses the car, some is drawn back down to the deck lid. if we put this spoiler down there it acts as an air dam (which is convenient because that is exactly what it is, it dams air, but is also correctly caleld a spoiler because it disrupts laminar airflow over the car) this air dam fills in the low pressure area over the deck lid and since air is smacking something attached to the car, it also adds downforce. please note, the airflow behind a spoiler is WORSE than with none at all. Just as the air was getting used to the shape of the car, this 'thing' got in its way. behind a spoiler it is very turbulent indeed, but its a tradeoff of traction vs. air induced drag. Stickin with the nascar example, you will note a trend that got ruled out of draggin the rear end of the 2nd gen luminas around the track. This made the rearward slope a big more gradual hence the airflow was cleaner than stock so the effects of the spoiler in terms of drag were lessened. If you follow the sport you hear of 2 distinct complaints: the required raising of the rear ends resulted in more drag which hurt chevy on super speedways, and the sometimes loss of spoiler size hurts traction - mostly on shorter tracks - a smaller spoiler at higher super speedway speeds on easier, higher banked turns does not make traction as much as an issue[2]. Whereas rear height is season long, nascar varies spoiler height race to race.

now lets add the wing...a wing by itself would be the best deal, it would really clean up the airflow over the car, yet push down nicely on the rear and hence except for the superbird (lookitup) is pretty much illegal on most race classes where 'stock' is part of the name or heritage. In the pics provided, note what the car was - fwd, likely with a 70/30 F/R weight split. not exactly something you want to try and make turns in. the spoilers AND wing really really add rearward downforce, but the combo mitigates drag, whatever drag is produced by the spoiler is taken care of by the wing, and the resulting drag I am sure is less.

Notes:

[1]: Completely unrelated, but proper injestion of the medium thru which a vehicle moves is important in one sport: jet boat racing. the suction provided by the pump pickup actually holds the watercraft down at the speeds they travel. hit a bump and break suction and the result is usually a spectacular 'blow over'. just thought id mention it

[2]: Consider drag racing, top fuel rails. those giant wings dont do much say 0-60 (which occurs in hundredths of a second) but greatly aid in the meat of the traction from 60-120, however at this point (about 1 second into the race) the wing becomes a liability, it produces way more than the needed downforce and hence a tremendous amount of drag. racers for decades (since 200mph became childs play) have wanted movable wings to trim the attack angle. nevermind that they would have to move with the speed of the control surfaces of an F15 given the sub 4-second pass.... Give them the movable wing and one has to wonder if the resulting forces would be able to be survived by humans....

[3]: (unannotated) due to cars like IRL being basically one large inverted airfoil (when I say inverted I mean with respect to airplane wings, the goal of an airplane is to go up, typically this is undesired in a race car) the entire race could be run on an upside down track. It would take no special spills on the part of the driver, but would make pit stops way more challenging if not outright entertaining.