Rear Wings on FF cars

[Aquarelle]

This question is aimed half at real life and half at GT5.

I often see FF cars such as Integras, 90s Sprinter Trueno's etc with really large wings, even in the pro scene.

I thought at first "They're just trying to show off 'cause wings are meant to be cool', how could rear down force help a front wheel drive car?"

I brushed it off for a long time but it's suddenly started getting to me again, I'm still learning so I could very well be wrong.

So, my question is. Is equipping a rear wing on a FF car helpful, or detrimental to its performance and how does it effect the control of the car through the corners?

 

[Kitten]

i always wondered this to...

i see like honda civic with huge wings... i just dont understand

 

[Tornado]

Lowers aerodynamic lift on the rear of the car (which is just as much of a problem on FF cars as it is on any other car), increasing stability at speed. Depending on the design, they may also decrease drag.


At least on ones that actually have function rather than just being aesthetic.

 

[daan]

I'm not sure of the answer, but I will point out that you're using the words "wing" and "spoiler" interchangeably when they are, and do, two different things.

Spoilers are often confused with wings, and the terms are frequently (yet incorrectly) used interchangeably. Spoilers increase grip by reducing the lift created by a car's shape, and also reduce drag by eliminating the induced drag associated with that lift. Wings increase grip by producing downforce, at the expense of additional induced drag.

I believe that an FF can benefit from a spoiler but not necessarily a wing.

 

[Aquarelle]

Lowers aerodynamic lift on the rear of the car (which is just as much of a problem on FF cars as it is on any other car)

Really? I suppose the problem is I'm not well versed in different drive trains.. I've spent all my time driving FR cars, but now I'm suddenly branching into MR and FF and it's a very strange new world. I wasn't expecting rear downforce to be as important for an FF since I thought it would be taking weight off the driven wheels and thus reducing traction..

I'm not sure of the answer, but I will point out that you're using the words "wing" and "spoiler" interchangeably when they are, and do, two different things.



I believe that an FF can benefit from a spoiler but not necessarily a wing.

Wow, I honestly had no idea! Thanks so much for this. I really do love learning new things and frankly I'm ashamed of myself to have been doing this for so many years..

Now I suppose I need to learn the different designs so I can actually figure out what kind these FF cars are using

EDIT: After some research, I've concluded the term I intended was "wing"

 

[daan]

I think that if the air can go underneath, then it's a wing. If it is just a lip that the air cannot go under, it's a spoiler. It's probably a lot more technical than that, but that's the basic explanation as I understand it.

 

[Aquarelle]

I think that if the air can go underneath, then it's a wing. If it is just a lip that the air cannot go under, it's a spoiler.

Yeah, that seems to be the unanimous verdict and I've edited my OP accordingly, thanks for pointing that out to me rather than letting it slide.

 

[Argon]

Go fast enough around a corner and every car will get to the limit of the "mechanical" grip across all wheels regardless of which are actually driving the car. It's true that an FF car would be more prone to front slip first because the fronts have to deal with power delivery too but regardless, all wheels will lose grip at some point and so aerodynamics (wings or spoilers) are just as useful on an FF car as it is on any other drive configuration.

 

[Famine]

So, my question is. Is equipping a rear wing on a FF car helpful, or detrimental to its performance

The answer to both is "Yes, depending on other factors".

 

[Tornado]

Really? I suppose the problem is I'm not well versed in different drive trains.. I've spent all my time driving FR cars, but now I'm suddenly branching into MR and FF and it's a very strange new world. I wasn't expecting rear downforce to be as important for an FF since I thought it would be taking weight off the driven wheels and thus reducing traction..

Well, first, it's not downforce in the sense you seem to be using it. It's rare for a car to produce positive downforce, and aerodynamic devices are generally designed to decrease lift more than anything else.


More important, though, is that stability at speed can be a problem regardless of the drivetrain of the car, and the balancing act is important. Too much of downforce on the front (or lift on the rear) can cause very nasty oversteer because the rear tires are unloaded, which only gets worse at speed (See: The Audi TT disaster, or the problems police departments were having with the Dodge Intrepid pursuit vehicles). Too much downforce on the rear (or lift on the front) can cause the car's steering to stop functioning properly, which also gets worse at speed. The rear tires on an FF car have a huge part in their handling capabilities, just like on any other car.







You know those videos where idiots put lunch trays under the rear wheels of their Honda Civics and drift them? A car with sufficiently high rear aerodynamic lift would do something like that at high speeds, so something to reduce lift (which is generally higher in the rear anyway) to a more balanced distribution F/R is beneficial; with the side benefit of lowering aerodynamic drag and everything inherent therein.

 

[Johnnypenso]

This question is aimed half at real life and half at GT5.

I often see FF cars such as Integras, 90s Sprinter Trueno's etc with really large wings, even in the pro scene.

I thought at first "They're just trying to show off 'cause wings are meant to be cool', how could rear down force help a front wheel drive car?"

I brushed it off for a long time but it's suddenly started getting to me again, I'm still learning so I could very well be wrong.

So, my question is. Is equipping a rear wing on a FF car helpful, or detrimental to its performance and how does it effect the control of the car through the corners?

I have tuned many cars in GT5 and have never come across a situation, nor do I know of any tuners that have, where tuning is limited in some way, that adding any wing to any FF and just about any other car for that matter, is beneficial. By tuning limited I mean PP limited, where you have a target to hit and adding downforce and trading off HP or weight to do it are your choices. Obviously if you can just add anything to the car you want this doesn't apply, but if you have to make a choice, even on FR's and MR's wings are not necessary and just slow the car down, because you can always tune in the stabliity into the rear of the car and not give up the HP you'd have to, to get the downforce.

 

[Aquarelle]

snip

I had always thought having the wing at the rear would speed up the front slip process, that's why it seemed fundamentally stupid to me for the longest time. I honestly wouldn't have guessed it would be just as important

The answer to both is "Yes, depending on other factors".

Would that be dependent on the conditions this figurative FF car is driving in, or limited to the car it's self? I do apologise I'm truly a novice to this drivetrain so I'm likely coming across as very dim

snip

Ohh I see, so it's more about reducing the loss of grip and weight at the front than 'increasing' it?

Even then I honestly didn't think of straight line instability, merely because all I was thinking about how it was pulling weight away from the front tires and reducing the traction for the driven wheels, that's why it was so fundamentally wrong in my head.

This just proves how far I have to go in my studies and I can't thank you enough for teaching me this. It's been baffling me for so long and I was just never in a group or community where I could ask it and not be stared at with a blank expression

snip

A really useful tip, I'll keep that in mind for when I eventually learn how to tune without google, advice like this is invaluable to me, thank you

Side note - Sorry for snipping your posts, just didn't want to make things too cluttered with so many quotes

 

[Famine]

Would that be dependent on the conditions this figurative FF car is driving in, or limited to the car it's self? I do apologise I'm truly a novice to this drivetrain so I'm likely coming across as very dim

The factors are... numerous.

Generally speaking, adding a wing or spoiler to anything is detrimental to the performance in terms of straight line speed - you're putting something in the air flow that changes the shape of the air around it causing drag and changing the drag coefficient. It has to carry the forces it creates, either spoiling the airflow or directing it for specific directional force and this increases the amount of power required to push it through the air at any given speed.

However, by changing the airflow and drag characteristics, you may affect the grip at high speeds, better enabling the car to transmit its power to the road and allowing it to go faster for the same power than without the wing. You may even reduce drag, with a certain design of spoiler.

A significant wing on the back of a FWD car may move the centre of gravity towards the back of the car and reduce the loading on the front tyres at speed - but at a 65:35 weight split, the car's got more load on the drive wheels than any FR car has...

And straight line speed is only one factor of performance. Wings affect braking (for similar reasons) and, most of all, cornering - spoilers too, just not so much.


So really it depends on the car and situation - and it may both hurt one aspect of performance while helping another (or help both, or hurt both).

 

[Aquarelle]

The factors are... numerous.

Generally speaking, adding a wing or spoiler to anything is detrimental to the performance in terms of straight line speed - you're putting something in the air flow that changes the shape of the air around it causing drag and changing the drag coefficient. It has to carry the forces it creates, either spoiling the airflow or directing it for specific directional force and this increases the amount of power required to push it through the air at any given speed.

However, by changing the airflow and drag characteristics, you may affect the grip at high speeds, better enabling the car to transmit its power to the road and allowing it to go faster for the same power than without the wing. You may even reduce drag, with a certain design of spoiler.

A significant wing on the back of a FWD car may move the centre of gravity towards the back of the car and reduce the loading on the front tyres at speed - but at a 65:35 weight split, the car's got more load on the drive wheels than any FR car has...

And straight line speed is only one factor of performance. Wings affect braking (for similar reasons) and, most of all, cornering - spoilers too, just not so much.


So really it depends on the car and situation - and it may both hurt one aspect of performance while helping another (or help both, or hurt both).

Thank you very much for elaborating, I'm sure you're very busy and it does mean a lot to me.

I'm really starting to understand all of this a lot more, amazing how years of confusion can be cleared up in 1 page..
It would seem my brain was over exaggerating the weight transfer to the exclusion of all other factors.

I think the most important part is the fact I've learnt so much more about how weight transfer and how aerodynamics effect a car, the things everyone has taught me in such a tiny window of time has improved my understanding of the physics of racing invaluably. Thank you ever so much!

 

[MrWednesday]

I think that if the air can go underneath, then it's a wing. If it is just a lip that the air cannot go under, it's a spoiler.

I don't think this is true. I believe some spoilers are shaped to direct air into the hole in back of a car, and this can only be done by allowing air to flow underneath the spoiler.

The distinction that I would make is thus:
* If it is an airfoil that generates lift by its shape, it's a wing.
* If it is not an airfoil and generates its effects by altering the direction of airflow, it's a spoiler.

 

[Exorcet]

Spoilers are often confused with wings, and the terms are frequently (yet incorrectly) used interchangeably. Spoilers increase grip by reducing the lift created by a car's shape, and also reduce drag by eliminating the induced drag associated with that lift. Wings increase grip by producing downforce, at the expense of additional induced drag.

This explanation is a bit off. Induced drag doesn't just come with wings, and "decreasing lift" is "increasing downforce" there is no practical different between the two.

High downforce (NASCAR or older sports cars) spoilers are very draggy, which is why they gave way to wings. Drag reducing spoilers (something you see on a hatchback) are different in that they're designed to promote flow separation to reduce suction around a corner or to create steady flow separation rather than chaotic and undteady flow which is bad for drag, lift, and stability. They will lower drag compared to no spoiler at all, but they will also probably produce induced drag in some form as that is the result of a pressure difference between two surfaces oriented roughly parallel to the flow.

I think that if the air can go underneath, then it's a wing. If it is just a lip that the air cannot go under, it's a spoiler.

Basically yes. A wing is a 3D extension of an airfoil. A spoiler is more of a protrusion.

*generates lift by its shape, it's a wing.
*generates its effects by altering the direction of airflow, it's a spoiler.

A wing does both. You don't get lift without momentum exchange, and that requires changing flow direction.

 

[generationlost]

Wings produce negative lift, or downforce for more stability at high speeds at the cost of more drag and a lower top end speed. A wing works based on Bernoulli's Principle. A wing on a car is pretty much an airfoil mounted upside down so that instead of producing lift (like on an airplane) it produces downforce (or negative lift). IIRC, a Spoiler is often designed to alter the airflow around the car to reduce drag and may or may not produce downforce.

Edit: Of course, there are "decklid" or "duckbill" spoilers, which are often flared lips integrated into the body at the back of the car. These can produce downforce depending on how they are designed. I know that the 2013 SRT Viper's duckbill-style spoiler produces downforce. However, these are often less effective at producing downforce than a properly designed wing.

 

[McClarenDesign]

Wings and spoilers can reduce drag on a car depending on how the interact with the pressures surrounding their area of influence. For instance, a low mounted wind can still relieve pressures under the car, thus reducing drag.

It's made even more complicated by the fact that air doesn't always behave like we think it should, and there are a multitude of reasons for it. One need only look at the Coander exhaust that was all the rage in F1. If you want expert answers, find an aerodynamicist.

For GT5, it's not likely that they'd model air as complicated as it actually is, so test for yourself and see what you come up with.

 

[niky]

Wings produce negative lift, or downforce for more stability at high speeds at the cost of more drag and a lower top end speed. A wing works based on Bernoulli's Principle. A wing on a car is pretty much an airfoil mounted upside down so that instead of producing lift (like on an airplane) it produces downforce (or negative lift). IIRC, a Spoiler is often designed to alter the airflow around the car to reduce drag and may or may not produce downforce.

Edit: Of course, there are "decklid" or "duckbill" spoilers, which are often flared lips integrated into the body at the back of the car. These can produce downforce depending on how they are designed. I know that the 2013 SRT Viper's duckbill-style spoiler produces downforce. However, these are often less effective at producing downforce than a properly designed wing.

Bernoulli be damned, a wing doesn't produce downforce because of air speed or pressure differential. Otherwise the humped shape of the car would practically guarantee flight.

Instead, wings and spoilers generate downforce by pushing air flow up, which generates the simple Newtonian reaction of pushing the car down.

Even a completely flat wing works as long as the angle of attack is correct. Some wings just happen to be curved to collect more air at the expense of a massive increase in drag. That angle of attack is why racing cars sometimes do spectacular flips when the front wheels go up, as the aero hits the right angle of attack to launch the car into the air.

Turn a car upside down and I can guarantee you the reverse airfoli shape would generate more lift than downforce.

 

[ChrisH]

... I often see FF cars such as Integras, 90s Sprinter Trueno's etc ...

Surprised no one caught this.

Just FYI, Sprinter Truenos are FR

 

[Tornado]

Surprised no one caught this.

Just FYI, Sprinter Truenos are FR

No one caught it because the Sprinter Truenos from the 1990s (as he indicated he was talking about) were, in fact, FWD.

 

[Exorcet]

Bernoulli be damned, a wing doesn't produce downforce because of air speed or pressure differential. Otherwise the humped shape of the car would practically guarantee flight.

Bernoulli applies to anything outside the boundary layer, including wings. Most cars produce lift because of their shape.

Some wings just happen to be curved to collect more air at the expense of a massive increase in drag.

Curvature reduces drag by limiting stagnation, delaying turbulent transition, and promoting attached flow. Extreme drag comes from high angle of attack because it induces flow separation and high induced drag.

There is also camber, which what I think you're actually taking about. The camber line shows the overall curvature of the airfoil, and it's true to an extent that camber leads to more drag, but it's not monotonic. Camber is better than no camber for drag and lift, and tricks like reversing camber at the trailing edge typically makes things even better. Severe camber typically goes hand in hand with high lift coefficients which can lead to drag, but it's not really until you get to high AoA that drag starts to get crazy high.

Turn a car upside down and I can guarantee you the reverse airfoli shape would generate more lift than downforce

An upside down car would be spectacular in many aerodynamic respects, but then you compromise the driver compartment, the chassis, and the low cg.

You may remember this post from the Deltawing thread

https://www.gtplanet.net/forum/showthread.php?p=6615541#post6615541

It's no coincidence the car looks like an upside down airfoil in the center.

 

[BongRipz]

Cars do generate lift and without proper aero to create downforce they do this @ high speed: https://www.youtube.com/watch?v=_o_0MBn9Lf4

 

[Aquarelle]

That video was.... humbling.. to say the least..
Not that I had any intention of doing 180 down a motorway but.. wow..

 

[Skygrasper550]

Surprised no one caught this.

Just FYI, Sprinter Truenos are FR

the Sprinter and Corolla cars from the 80's, yeah sure they are FR. But after that, all Sprinter/Corolla models Toyota made (starting from the 90's) are FWD. 👍

The E80 Corolla (the ever-famous AE86 being one of those) was the last generation Toyota Corolla to become RWD. After that, the E90 Corolla and all generations after that have been made with FWD as their standard layout.

back on-topic...


So, let me get this straight, a "spoiler" enhances airflow around a car but doesn't necessarily produce downforce. But a "rear wing" will always produce downforce, and drag to come along with that. That is what I've always thought of. Am I right?

 

[ChrisH]

the Sprinter and Corolla cars from the 80's, yeah sure they are FR. But after that, all Sprinter/Corolla models Toyota made (starting from the 90's) are FWD. 👍

Ah, I skipped over the year part, because the 90's Sprinters were nothing to write home about

 

[Skygrasper550]

Ah, I skipped over the year part, because the 90's Sprinters were nothing to write home about

which is why Toyota developed the FT-86.

 

[Exorcet]

So, let me get this straight, a "spoiler" enhances airflow around a car but doesn't necessarily produce downforce. But a "rear wing" will always produce downforce, and drag to come along with that. That is what I've always thought of. Am I right?

I was going to show images, but the internet doesn't know what a spoiler is. Type in wing, and you get wings. Type in spoiler... and you get wings.

The two originated in aviation. A wing is, well a wing. A spoiler on a plane is a device that reduces (or spoils) lift to make landing easier.

The ones that open upwards are spoilers. They can serve a similar purpose on cars, creating high pressure on upper surfaces to generate downforce. However, they can have another use, which is controlled flow separation. Separation is when the air stop following the contours of the surface and leaves the body.



The colored slices in these images are velocity. The blue regions behind the cars are wakes, which is areas where the flow has separated. The blue car has a low drag quasi steady wake. The red car has a high drag unsteady wake (mostly from the diffuser). Spoilers allow you to separate the flow at angles where it is steady and low drag.

What makes a spoiler a spoiler is that it's integrated into the car body, so it can only have smooth attached flow on one side (usually the upper/front surface). Air cannot travel smoothly along the bottom and rejoin the air on the top because there is no way for it to reach the bottom without separating.

A wing on the other hand is an airfoil (2D closed shape) extruded in the third dimension that forms a body that has attached flow on all surfaces.

http://en.wikipedia.org/wiki/Airfoil

Don't try to figure out what's what by what they do to car performance, look in terms of their impact on the surrounding flow (especially the wake behind them, if any) and their 2D profile. A wing has an airfoil as a 2D profile. Cut a car with a wing down the center, and you'll see the airfoil sitting by itself (F1 car).

Cut a car with a spoiler down the center, and you won't be able to get the car and spoiler as separate entities. The spoiler will still be attached to the car (NASCAR).

 

[Johnnypenso]

Bernoulli be damned, a wing doesn't produce downforce because of air speed or pressure differential. Otherwise the humped shape of the car would practically guarantee flight.

Next time I'm on my way to Mexico I'm going to look out the window at 35,000 feet and pray that Bernoulli is not damned...lol...

 

[GrUBbY]

If I'm not mistaken, the spoilers on the tops of airplane wings are "brakes". Flaps that pop up to disrupt airflow and increase drag slowing down the mass. Fighter jets have similar ones usually toward the rear of the plane. This also helps their stability.

Something that helps me understand this better is 2 examples. Top fuel dragsters have a wing. Until they get past a few hundred feet and actually generate speed, they don't do a whole lot in terms of downforce. Once they hit that sweet spot and the clutch hits full lock, the downforce can be measured in tons. Which brings me to my other example. F1 cars also have wings. Now the rear wing may be for downforce, forgive my ignorance if it's not, but if IIRC the front wing doesn't. It creates a vacuum under the car by manipulating the airflow. The last F1 race I watched on TV (India), David Hobbs made the statement if an F1 car can maintain speed it is theoretically possible to drive on the ceiling. Please correct me if I'm wrong because I'm intrigued by the concept as well and seek pertinent, viable and correct information to better educate myself.