FWD spoilers

[KnifeEdge_2K1]

Ferrari 360 creates downforce mostly using ground effects, the downforce created by the fastback design and lipped rear spoiler is miniscule compared to the rear diffuser

check out the 360 Challenge Stradale from the back

there is a "multi layered" rear difuser, so cool

[RacingManiac]

spoilers on the road usually dont create downforce, cuz actual downforce comes hand in hand with drag

things like the spoilers on the lancer evolution and subaru impreza are designed to "clean up the airflow" as some of you have pointed out, sometimes actually LOWERING drag while lower the lift coefficient

just as in racing the most thing to do to increase downforce while increasing drag minimally is use ground effects, basically a front spoiler to make air go around the car instead of under it, and a rear diffuser to make the air "expand again" creating suction to the road

lowering the car also helps this for obvious reasons

A Spoiler will some times lowers drag by allowing the flow to reattached. But on a Evo or STi, that is an actual air foil, a wing. A diffuser does not generate downforce, but rather the throat of the under body section, a diffuser allows the flow to decelerate and rejoins the normal flow thus not to add more drag and allows for the entire underbody works more effectively.

Its not that hard to make a wing that works, but the problem being how well it works. But I think in general they do. The fact that a car's shape in general creates positive lift, any thing to break off the flow will kill some of that lift, but adding drag in process.

Interesting thing about that though, on the new Evo MR or whatever, with its vortex generator on the roof, which actually creates turbulent flow, which(according to my fluid class last week, on the subject of vortex generator, which has been around for a long time) can actually stays attach for longer length along the body's boundary layer and thus reduce drag.....and in Evo's case, reduce the drag that will probably be caused by the big rear wing, and since the flow will be better attached, allows it to work better too....

[RacingManiac]

BTW, I think 360 CS's rear is not actually "multi-layered", although I am not entirely sure. As the new one actually goes over(or "under") the old tunnel. As the ride height are lowered, your diffuser ceiling is supposed to lower too to compensate.

[KnifeEdge_2K1]

A Spoiler will some times lowers drag by allowing the flow to reattached. But on a Evo or STi, that is an actual air foil, a wing. A diffuser does not generate downforce, but rather the throat of the under body section, a diffuser allows the flow to decelerate and rejoins the normal flow thus not to add more drag and allows for the entire underbody works more effectively.

Its not that hard to make a wing that works, but the problem being how well it works. But I think in general they do. The fact that a car's shape in general creates positive lift, any thing to break off the flow will kill some of that lift, but adding drag in process.

Interesting thing about that though, on the new Evo MR or whatever, with its vortex generator on the roof, which actually creates turbulent flow, which(according to my fluid class last week, on the subject of vortex generator, which has been around for a long time) can actually stays attach for longer length along the body's boundary layer and thus reduce drag.....and in Evo's case, reduce the drag that will probably be caused by the big rear wing, and since the flow will be better attached, allows it to work better too....

hmm i thought rear diffuser creates downforce since the air will need to expand which means lower pressure

[F1_Master]

Matra, maybe you could answer this.

On the Escudo Pikes Peak car (from GT3), why does it have such a large spoiler. I don't think its FWD. Or is it?

I mean, that spoiler is HUGE!

[KnifeEdge_2K1]

err nm i just brushed up on my physics

downforce is created by the venturi tunnels

diffuser just decreases drag by melding the airflow

[Coventrysucks]

On the Escudo Pikes Peak car (from GT3), why does it have such a large spoiler. I don't think its FWD. Or is it?

It is 4wd, but with 900 - 1,000bhp, trying to go up a largely gravel and dirt roads to the top of a 4300m (14,000ft) mountain.

So it needs lots of downforce to get as much grip on the loose surface as possible.

As you go up the mountain, the air pressure decreases. This leads to a drop off in power, and aerodynamic efficiency. A small wing which would suffice at lower altitude is rendered ineffectual. So the simple solution is an absolutely huge wing.

It is the same reason why you can't get choppered to the top of Mount Everest - the rotor blades can't generate enough lift in the thin atmosphere.

[RacingManiac]

the proper diffuser design, along with the rake of the floor, is also important as it will determine the location of center of pressure which is crucial in determining the aerodynamic balance between front and rear axle...

[Alastor]

the proper diffuser design, along with the rake of the floor, is also important as it will determine the location of center of pressure which is crucial in determining the aerodynamic balance between front and rear axle...

Suspension design is also important for not only controlling the ride height to maintain the ground effect but also for controlling pitch to minimize dynamic changes in location of the center of pressure.

hmm i thought rear diffuser creates downforce since the air will need to expand which means lower pressure

For most race car aerodynamics the flow is consider incompressible (no change in density) and so Bernoulli’s equation is applicable. As a result the increase in cross-sectional area at the diffuser causes a decrease in flow velocity and increase in flow pressure.

Interesting thing about that though, on the new Evo MR or whatever, with its vortex generator on the roof, which actually creates turbulent flow, which(according to my fluid class last week, on the subject of vortex generator, which has been around for a long time) can actually stays attach for longer length along the body's boundary layer and thus reduce drag.....and in Evo's case, reduce the drag that will probably be caused by the big rear wing, and since the flow will be better attached, allows it to work better too....

Useful vortex energy usually comes in two forms. The first as you mentioned involves delaying separation. In this method a vortex is used to mix the high-speed air flow with the less energetic turbulent air flow, and originated from aircraft airfoil design. A picture of a vehicle application can be found here:

http://forums.evolutionm.net/showthread.php?t=107303

The second method involves larger vortices that are usually generated on the side of the vehicle. The larger vortices draw flow into a section of the wake that would otherwise be separated flow. For example the link below shows the separation area “A” has been reduced by using vortex “C” to direct slipstream “D”.

http://img73.exs.cx/img73/3581/flow.jpg

Another interesting application of vortices is use for controlling spanwise flow across an airfoil. A slot is introduced into the leading edge of the airfoil and at larger angles of attack a high pressure vortex is created. This vortex acts as a transparent wall to prevent spanwise flow as would a fence. I don’t know of any automotive application but it is interesting nonetheless.

[KnifeEdge_2K1]

i'm not sure if this is correct but i think the 360 Modena or Challenge Stradale (cant remember) and the Porsche CGT use side mirror induced vortexes to direct airflow into the side intakes

[F1_Master]

Wow. There's so much going on with these cars at high speeds. I had no idea they made the side mirrors that way too.