Rear Wings

[Joey D]

One thing to consider with the cost of a rear wing/spoiler is paint. The two spoilers I got for my car were cheap but it's $300 to get them painted, although I have metallic paint which bumped the price up.

 

[Aquarelle]

One thing to consider with the cost of a rear wing/spoiler is paint. The two spoilers I got for my car were cheap but it's $300 to get them painted, although I have metallic paint which bumped the price up.

Ouch.. although I would presume they come pre-prepared for painting? or do you need to prepare the surface yourself?

I've got quite a bit of experience with painting and my friend has an air gun I can use as long as I have the paint, there's a store near me that will mix up any paint code so it shouldn't be a problem.

Out of interest, is it difficult to paint the carbon fiber wings?

 

[Joey D]

Yup both of mine came primered but being from China they were exactly stellar. The paint shop has a bit of work to do on them. I'm sure if you buy non Chinese knock off stuff they'll be better prepped. In the end though I'm still paying less than a non painted spoiler from Ford so it's all good.

 

[Aquarelle]

Yup both of mine came primered but being from China they were exactly stellar. The paint shop has a bit of work to do on them. I'm sure if you buy non Chinese knock off stuff they'll be better prepped. In the end though I'm still paying less than a non painted spoiler from Ford so it's all good.

Fair enough 👍 I prefer using the real thing personally, paying the extra for better quality just makes sense in my mind. Plus I want to support the Japanese domestic market and the tuners associated with it, so I'll buy genuine products for that reason as well. But that's beside the point obviously I don't think any worse of you for what you do with your money, that would just be absurd.

 

[Exorcet]

Kia ora guys.

I don't often stroll down here but I have a question that I'm not sure how to word for google

It revolves around Wings (Though I'd imagine you figured that out from the title) or more specifically, the struts attaching the wing to the car.

My question is simple, I'm looking at getting a wing and I want to know which is seen as the superior 'style', centred struts or having them as close to the edge of the boot/trunk as possible.

I'm probably going to answer my own question here but I would think that having centred struts would make the edges of the wings flex more (Which I would imagine is a bad thing since it would cause instability) but I'm still learning about aerodynamics and the science behind it unfortunately.

It basically doesn't matter structurally. The bending moment on the wing is handled by the spar. A good wing will be strong enough to be rock steady.

Most force is generated at the center of the wing. On the other hand tip vortex produce the majority of drag and endplates help combat tip vortex formation.

Your car has enough power that additional downforce would help?

Pretty much every car does.

A wing or aerodynamics has nothing to do with power.

How effective it is for your car will depend on power, in an indirect way.

A rear spoiler only gets it max. downforce at around 160-180 kmh. (it gets a bit before those speeds, but nothing world changing, though it can be felt)

I'm not following. There is no "max downforce". There is no minimum speed for downforce either. You can feel it at any speed, depending on how much you're generating.

But like the others said, putting the money first in the suspension might be the better idea

Skimming the thread, I'd probably go with this. If your car is having trouble at road speed, look at the suspension and tires first.

 

[Aquarelle]

It basically doesn't matter structurally. The bending moment on the wing is handled by the spar. A good wing will be strong enough to be rock steady.

Wow I really didn't expect them to be that strong! though that's made of carbon fiber from the looks so perhaps it's not that surprising. Cheers though for answering the initial question, I was still rather curious about that 👍

Guess it was simply aesthetics after all

Skimming the thread, I'd probably go with this. If your car is having trouble at road speed, look at the suspension and tires first.

It's not so bad at 'road speeds'. It's not scary when I'm going down a road at the speed limit the signs leading up to the corner suggest to take it at.

The problem comes up when I'm exceeding a safe and steady cornering speed (In a safe and controlled manner and environment)

 

[Eunos_Cosmo]

Safe and controlled manner and environment and the public road cannot be mentioned in the same sentence. Spirited driving is one thing, endangering other people is another. Keep it safe. I have a feeling your driving, more than anything else, is contributing to the unsteady feeling of your car.

Lift off/weight transfer oversteer is extremely dangerous, especially in a short wheelbase, mid-engined car like an MR2. Hell my brother managed to spin off the road (catastrophic oversteer) in a front engined, front wheel drive Integra because of weight transfer. You are clearly driving above either your car's ability or your ability, or both if you are "exceeding a safe and steady cornering speed" as you yourself state. And doing so with worn out suspension is just insanely stupid.

 

[Aquarelle]

Safe and controlled manner and environment and the public road cannot be mentioned in the same sentence. Spirited driving is one thing, endangering other people is another. Keep it safe.

I made no mention of exceeding the speed limit on public roads or endangering others o.O

New Zealand may be primative compared to Japan, America or Europe but we do have race tracks

Edit: responding to addition to post.

Lift off/weight transfer oversteer is extremely dangerous, especially in a short wheelbase, mid-engined car like an MR2. Hell my brother managed to spin off the road (catastrophic oversteer) in a front engined, front wheel drive Integra because of weight transfer. You are clearly driving above either your car's ability or your ability, or both if you are "exceeding a safe and steady cornering speed" as you yourself state. And doing so with worn out suspension is just insanely stupid.

We really haven't met under the best circumstances everything I say is making you think worse and worse of me.

No I understand weight transfer, not to be big headed but my driving ability is really quite good. It's only in this car that I've ever been scared in high speed corners.

By "Safe and steady cornering speed' I'm meaning going around a corner at 65-80, like how the signs on the side of the road suggest you should. Sort of like how you'd imagine an older person to drive.

If I were to go around a circuit in a manner I'd deem safe for if it were a real road; It would be fine. However when pushing it it feels dangerous, that's why I was thinking downforce would be the solution.

 

[avens]

is it true that in new zealand you can import any car without any restriction or permission required? Usual ones are used cars, years passed from manufactured, right hand drive, regulations in general (safety, emissions, etc.)

 

[Aquarelle]

is it true that in new zealand you can import any car without any restriction or permission required? Usual ones are used cars, years passed from manufactured, right hand drive, regulations in general (safety, emissions, etc.)

That's correct, you can register pretty well anything over here, even a car you've built in your shed with questionable technique.. There's no restriction on tuning that I know of also. As long as all its components are in safe working order you'll pass your registration.

My step father apparently has a mustang that he got shipped over here, didn't even convert it from left hand drive and it's perfectly legal. Unfortunately I haven't spoken to him in years so I can't weasel my way into the drivers seat.

 

[Ibonibo]

I'm not following. There is no "max downforce". There is no minimum speed for downforce either. You can feel it at any speed, depending on how much you're generating.

Yes it's speed dependant, or rather wind dependant. Why do you think automatic spoilers stay hidden at low speeds? Because it's useless. Or even unhelpful as it increases fuel consumption, due to a higher CV, without generating downforce.

The more wind the spoiler gets the more downforce you get. The rule of thumb is around 180kmh or 100 mph where it hits it's stride. But that depends clearly on the setup of the spoiler.

I very much doubt you can feel a spoiler at 5 mph

Your last sentence pretty much states that (more or less) : "depending on how much you're generating", which depends on the wind, aka speed

It's a reversed plane wing, and planes don't fly without wind, speed or air (which ever you prefer)

 

[Ridox2JZGTE]

UrieHusky, any chance you ever been doing track days at Taupo Race track ? If you bring your SW20 MR2 to the track, you should at least upgrades the suspension first, I don't think that the rear spoiler would do much at less than 100 km/h around medium or low speed corners. But it will help stability above 160km/h on the straight or high speed corners.

A better tires ( lower profile and more tread width ), strut braces, better spring and damper, some extra rigidity at the front and rear suspension bushing and joints would make the car more stable than a spoiler could do at such speed. Whiteline sold great 3 point sway bars for SW20, cheaper upgrades. Also be sure to have the car properly aligned, toe and camber are important for an MR

 

[Aquarelle]

UrieHusky, any chance you ever been doing track days at Taupo Race track ? If you bring your SW20 MR2 to the track, you should at least upgrades the suspension first, I don't think that the rear spoiler would do much at less than 100 km/h around medium or low speed corners. But it will help stability above 160km/h on the straight or high speed corners.

A better tires ( lower profile and more tread width ), strut braces, better spring and damper, some extra rigidity at the front and rear suspension bushing and joints would make the car more stable than a spoiler could do at such speed. Whiteline sold great 3 point sway bars for SW20, cheaper upgrades. Also be sure to have the car properly aligned, toe and camber are important for an MR

Nah I'm nowhere near Taupo I've only been there once on a road trip with a friend.

I've been dying to upgrade the suspension so that I can set up the handling how I want it, unfortunately money hasn't been allowing it. Moving into an apartment complex is chewing my money because parking is 55 a week.

Pretty much everything you've listed are things I want to do, it's just a case of when I can do it and what to do first. The alignment hasn't been done since I got it and the paperwork doesn't list anything outside of when it got serviced.. I think I might run down and get that done today as well actually, it never occurred to me because of everything else on my mind.

 

[Exorcet]

Yes it's speed dependant, or rather wind dependant. Why do you think automatic spoilers stay hidden at low speeds? Because it's useless. Or even unhelpful as it increases fuel consumption, due to a higher CV, without generating downforce.

Moveable spoilers are mostly gimmick/fuel economy. Some of the more recent ones on high end cars seems to be more useful though.

Yes, lift goes with velocity squared - which is why I did not understand your statement "A rear spoiler only gets it max. downforce at around 160-180 kmh." Because the downforce is going to keep growing as the speed goes up, barring some pretty extreme extremes for a road car.

The more wind the spoiler gets the more downforce you get. The rule of thumb is around 180kmh or 100 mph where it hits it's stride. But that depends clearly on the setup of the spoiler.

The rule of thumb is L = .5*rho*cl*V*V*A

rho being air density, V being speed, A being wing size, and cl being lift coefficient (how good the wing is at generating force)

With enough cl you can generate enough downforce to drive a car upside down in a tunnel at 30 mph. That's unlikely though. More likely is that you can design a wing for low speed applications and get useable downforce at 30 mph. Useable downforce would depend on the car's power (to fight drag), weight, and the wing performance.

30-60 mph wing

I very much doubt you can feel a spoiler at 5 mph

You can, but it needs to be designed for it. This is rare though.

Your last sentence pretty much states that (more or less) : "depending on how much you're generating", which depends on the wind, aka speed

Or the CL.

It's a reversed plane wing, and planes don't fly without wind, speed or air (which ever you prefer)

I agree, but that speed can be extremely low.

I didn't mean to turn this into an argument, just correcting something small. Your statements are somewhat correct (there isn't really a max downforce) for average road cars with limited aero. But not in the general case.

If I were to go around a circuit in a manner I'd deem safe for if it were a real road; It would be fine. However when pushing it it feels dangerous, that's why I was thinking downforce would be the solution.

Well for a track wing be careful about a few things. The spoiler Luminis posted for example looks like it might be stalled by the roof the car. You probably want a fairly high wing.

 

[Aquarelle]

Well for a track wing be careful about a few things. The spoiler Luminis posted for example looks like it might be stalled by the roof the car. You probably want a fairly high wing.

The area behind the rear window is a low pressure zone similar to a ute (Pickup, flatbed, whatever your regional equivalent I'm sure you can figure it out) however that low pressure zone dies out before the area where the wing is located, so that spoiler would still (assuming my understanding of aerodynamics and airflow is correct) be effective.

(I've tried to find some wind tunnel footage or diagrams displaying the air flow to show you but I can only find them for older generations of the MR2)

 

[Exorcet]

Alright, I wasn't sure if that was the case or not because the angle looks so low.

About images, I might try to run this in CFD later out of curiosity.

 

[Keef]

Urie, I understand where you're coming from and the strength question is a good one. I've never seen this tested but I have to assume original products are quite strong. Japanese time attack cars especially use them to generate 500+ pounds of downforce at speed. The key is to mount the struts far enough apart to help spread the load across the wing spar so neither center-mounted or edge-mounted struts are the best idea. As you can see on the Viper picture, it looks like the struts are set about 1/4-width in from each edge, with about 1/2 width in between the the two. It makes sense.

As for realistic fun and performance improvements, there's a lot more to be gained from a decent tire and suspension setup. Tires, especially, should be the first step if you want large grip gains at all speeds. Unless you're routinely cornering at 100+ mph then a typical low-camber aftermarket wing will not have a large effect on stability. It will have an effect, yes, but in my opinion not enough to justify the price when you could have a sweet set of barely-legal summer tires for the same money and feel the difference at 25 mph.

A car like the SW20 already has a decently stable aerodynamic profile, like my RX7 which you can click on in my signature. My car goes straight as an arrow at 130 mph, and while I've never ran on a large track I can expect fairly good stability thought 80-100 mph sweepers. I have a few friends who race Spec E30 and their cars are totally stable on R-compound tires despite being shaped like bricks.

 

[Aquarelle]

Alright, I wasn't sure if that was the case or not because the angle looks so low.

About images, I might try to run this in CFD later out of curiosity.

I'd love for you to get back to me with the results

Urie, I understand where you're coming from and the strength question is a good one. I've never seen this tested but I have to assume original products are quite strong. Japanese time attack cars especially use them to generate 500+ pounds of downforce at speed. The key is to mount the struts far enough apart to help spread the load across the wing spar so neither center-mounted or edge-mounted struts are the best idea. As you can see on the Viper picture, it looks like the struts are set about 1/4-width in from each edge, with about 1/2 width in between the the two. It makes sense.

As for realistic fun and performance improvements, there's a lot more to be gained from a decent tire and suspension setup. Tires, especially, should be the first step if you want large grip gains at all speeds. Unless you're routinely cornering at 100+ mph then a typical low-camber aftermarket wing will not have a large effect on stability. It will have an effect, yes, but in my opinion not enough to justify the price when you could have a sweet set of barely-legal summer tires for the same money and feel the difference at 25 mph.

A car like the SW20 already has a decently stable aerodynamic profile, like my RX7 which you can click on in my signature. My car goes straight as an arrow at 130 mph, and while I've never ran on a large track I can expect fairly good stability thought 80-100 mph sweepers. I have a few friends who race Spec E30 and their cars are totally stable on R-compound tires despite being shaped like bricks.

(So freaking envious of your FC, they're incredibly expensive here but I plan on getting one (or an FD) when I move to Japan)


I really appreciate your insight, I'll look into other methods of solving the problem outside of aerodynamics.

I came into this question uneducated on the subject and have left with a wealth of knowledge on the subject that I can't thank you all enough for.

You've all contributed to my growth as a mechanic, a tuner and a driver and for that there are no words (or silly emoticons) for my gratitude.

 

[Luminis]

The area behind the rear window is a low pressure zone similar to a ute (Pickup, flatbed, whatever your regional equivalent I'm sure you can figure it out) however that low pressure zone dies out before the area where the wing is located, so that spoiler would still (assuming my understanding of aerodynamics and airflow is correct) be effective.

Posts rear wing based on personal aesthetic preference

http://[domain blocked due to malware]/images/160x/1031.jpg

isn't completely non-functional.

 

[Aquarelle]

Posts rear wing based on personal aesthetic preference

http://[domain blocked due to malware]/images/160x/1031.jpg

isn't completely non-functional.

Shocking and yet true (Again, assuming my understanding or aerodynamics and airflow is correct)

 

[Zenith]

As for realistic fun and performance improvements, there's a lot more to be gained from a decent tire and suspension setup. Tires, especially, should be the first step if you want large grip gains at all speeds. Unless you're routinely cornering at 100+ mph then a typical low-camber aftermarket wing will not have a large effect on stability. It will have an effect, yes, but in my opinion not enough to justify the price when you could have a sweet set of barely-legal summer tires for the same money and feel the difference at 25 mph

This. An wing will need to be tall enough to raise out of the turbulent air flow behind the cockpit in order to be really effective and the car in question could benefit far more from spending that money somewhere else.

 

[Exorcet]

I'd love for you to get back to me with the results

Sure, but keep in mind this will not be super accurate. I don't have a full model of the car, and I can only use my personal resources for this so I'm limited in terms of hardware/software. It's more for fun than anything else.

Here is the model I made.

from this

 

[wrapture]

Another MR2 owner

I would stick with stock, unless you could get one with the same style but a little taller.

 

[Monatsende]

This threads evolves...

Does anybody own a wind tunnel to make practical experiments?

 

[Aquarelle]

Sure, but keep in mind this will not be super accurate. I don't have a full model of the car, and I can only use my personal resources for this so I'm limited in terms of hardware/software. It's more for fun than anything else.

Looks good! 👍

Another MR2 owner

I would stick with stock, unless you could get one with the same style but a little taller.

We can be girly hair dressers together!

That's the plan, I didn't realise there were aftermarket spoilers that resembled the stock spoiler while offering more downforce. I mainly see the ones on struts either in black/carbon fiber or painted to match the body colour.

This threads evolves...

Does anybody own a wind tunnel to make practical experiments?

It was given a 1up

I wonder.. I live near the university in my city but I don't remember if it's AUT that has a wind tunnel or Otago..

 

[Exorcet]

Just remember that a Wind Tunnel has its own problems when trying to generate correct numbers. Namely blockage and properly simulating the effects of moving ground.

You can also try to use a scale model in a water tunnel if you make the scale such that the Reynold's number is the same. This will let you use a much smaller model. It also provides a nice way of simulating a moving road. If you place two identical models on each other wheels, the plane of symmetry between then becomes a very good place holder for moving ground plane.

CFD says that you would need a high mounted wing. The stock spoiler may not be completely ineffective, but it's in the wake of the rear window and not able to generate much force.

However, while the flow results look reasonable, forces were not. I was getting about 200-250 lbf of drag at 100 mph which is about 25%-50% higher than it should be. I'll have to look into why the CFD is giving me that number.

 

[Famine]

Just for reference, this:

is a spoiler, not a wing. Wings can be (and usually are) both, but spoilers are just spoilers. And that's just a spoiler.

 

[Exorcet]

I usually go by whether or not the majority of the part is isolated or connected to the car when you take 2D slices oriented length wise along the car. A wing would be a 3D extension of an airfoil with its own stagnation points while a spoiler would be an extension of the car.

Since there's air all around the part on the rear of the MR2, I'd say it could be wing. I've never really seen a solid definition separating one from the other (except for aircraft).

 

[1stlsx]

EXORCET- Does the gap under the spoiler not make a difference?

 

[Exorcet]

EXORCET- Does the gap under the spoiler not make a difference?

In terms of how I classify it? Or in terms of performance?

The answer is yes. The gap underneath is why I'd say you could call the one pictured above a wing. It also allows for pressure recovery on the rear/underside surfaces which reduces drag.