Spoiler alert

[Petrus]

Any of you have a silly large wing mounted of the back?

It simply keeps bugging me. Any first hand experience would be most welcome.

Thanks.

[Snelbaard]

just a Luxuryparts duck tail

[Topdownman]

SpyderLee on youtube did a video on fitting one to his car.

[Petrus]

SpyderLee on youtube did a video on fitting one to his car.

Thanks, yes, but no feedback on the effect though.

The ducktail, Boris, doés have a marked effect in reducing sensitivity to sidewind. It is almost the same, and not surprisingly, as on the Audi TT where Audi released it as an upgrade upon complaints of owners.

I have a small Kamm/Gurney type rubber lip on the back and despite being such a little thing is has noticeable effect.
Hence my quest for first hand feedback on the bl@@dy big wing.

[Petrus]

Back then Lee had what I would honestly call the best looking Spyder I've ever seen.

´Best looking´ is subject to taste.
He sure made it look spectacular and coherent which is not an easy feat to combine.

The wing of that stage is the one I wánt. 3D PU foam = light!

[Petrus]

You mean you want Lee's wing (early or current) or the one from the silver car?

The one Lee had on the photo.

[Petrus]

Too bad it can't be homologated, at least not here.

That is no issue for me.
Just take out the bolts through the two deck mountings and you are ready to go. As long as you stay within the car´s dimensions the plod is not going to stop you.

[Petrus]

Seems I´m stuck without feedback from the MR2 side.

The MX world has more info. The redux is that the 3D Voltex GT model and copies of such are rather effective in adding rear downforce from some 80 km/h without adding significant drag up to some 160-170 km/h.

Btw. the lighter the car the greater the effect of the aero mods. which stands to reason as at the same speed the aero forces ´weigh´ heavier respectively to the car´s mass: a 100 kg downforce has more effect on a 900 kilo car than on a 1200 kilo car.

Oh, I forgot to mention that several times in several aero threads; néver éver mount the wing with the supports behind the rear axle.  Chassis mounting is good but on the rear outriggers is a grave mistake; the downforce will create a momentum lífting the front. 

What´s not to love:

[Nvy]

Seems I´m stuck without feedback from the MR2 side.

The MX world has more info. The redux is that the 3D Voltex GT model and copies of such are rather effective in adding rear downforce from some 80 km/h without adding significant drag up to some 160-170 km/h.

Btw. the lighter the car the greater the effect of the aero mods. which stands to reason as at the same speed the aero forces ´weigh´ heavier respectively to the car´s mass: a 100 kg downforce has more effect on a 900 kilo car than on a 1200 kilo car.

Oh, I forgot to mention that several times in several aero threads; néver éver mount the wing with the supports behind the rear axle.  Chassis mounting is good but on the rear outriggers is a grave mistake; the downforce will create a momentum lífting the front. 

What´s not to love:

One of the proven wings that works is the Honda S2000 CR wing. We could check for specs and find something similar. Our backend is different but id imagine that it will still work.

[Petrus]

One of the proven wings that works is the Honda S2000 CR wing.

But for the ´half´side plates a very much akin design.

[105e]

I dont think mounting it far back would actually lift the front. I see the seesaw theory but in practice surely the suspension would just compress, which may give the impression that the nose is higher.

[Petrus]

I dont think mounting it far back would actually lift the front. I see the seesaw theory but in practice surely the suspension would just compress, which may give the impression that the nose is higher.

It is mathematics; leverage. You can even calculate it.* Furthermore wind tunnel testing confirms it. It´s very real and should be taken into account.

Compressing the rear creates another unwanted effect by tilting the floor of the car; lift under the whole vehicle. The inverse of having the nose a bit lower creating lower pressure.

Now, I will add a caveat to the ´never ever´: unless you fit an even bigger splitter/scoop at the front.

Aero is not complicated and real fun although you cán get it real wrong ;-)

* same as taking weight off behind the rear axle = ´adding´ (relatively) weight to the front.

[Snelbaard]

Front axle lift would be calculated like this:

FL = DF x RO / WB

Downforce = DF
Distance between rear axle and Rear wing = RO
Wheelbase = WB
Front axle lift = FL

So it would most of the time be negligible, and this assumes you have no rear suspension. Like 105e said, rear suspension compression would soak up most of that downforce anyway, so that only veeeery little gets 'seesawed' to the front axle.

In reality it is usually preferred to have the rear wing far back, as the distance from the wing to the rear axle multiplies its its force on it. It's a balancing act between that, rear suspension compliance and wheel base.

[Petrus]

Front axle lift would be calculated like this:

FL = DF x RO / WB

Downforce = DF
Distance between rear axle and Rear wing = RO
Wheelbase = WB
Front axle lift = FL

So it would most of the time be negligible, and this assumes you have no rear suspension. Like 105e said, rear suspension compression would soak up most of that downforce anyway, so that only veeeery little gets 'seesawed' to the front axle.

In reality it is usually preferred to have the rear wing far back, as the distance from the wing to the rear axle multiplies its its force on it. It's a balancing act between that, rear suspension compliance and wheel base.

Whoa, I never wrote not having the wing back. I wrote ´support´!! It´s where the force acts on the chassis what counts.

The effect is larger than you think.
The Spyder has a 245 cm. long wheelbase. Pushing the chassis down only 24,5 cm behind the rear axle thus lifts the front by 10%. That is not negligeble. It needs be counteracted by a larger downforce at the front. That will reestablish the balance but the price is a double unneccessary air resistance.

Same thing compressing the rear more than the front, taking the rear relatively up. As I wrote, that can create lift under the whole car.  Having rear supension makes it worse!

I will have a look on youtube. I remember a good illustration in a wind tunnel.

Found it:
https://www.youtube.com/watch?v=Pgpawejpi6o&t=359s

and for those doubting the huge effects of little aero changes; look at the wind thing behind the seats of even more clear mongos.
The ducktail needs no explanation; Audi came up with that on the TT and it saved lives!!!

[Snelbaard]

Of course I meant the Rear wing support location.

But let's be real here. I wrote 'most of the time' for a good reason. Most of the time you will not be going at such speeds that would make this effect problematic for our cars. Say you generate 50kgs of downforce, which I think is a generous estimate, you would theoretically cause a lift of 5 kg's on the front axle. Again, this is assuming the rear suspension is rigid, which it is not. Let's once again be generous and guess that 3 kg's of lift actually make it to the front axle. I wouldn't lose sleep over that.

The reverse rake this causes would indeed cause further aerodynamic lift, but I wouldn't be surprised if rear wings such as these would be accompanied by front dive planes to offset these effects.

I am aware that subtle changes can have pronounced consequences, but that does not make it true that every small change has such effects, especially at our relatively pedestrian speeds.

[Petrus]

In reality it is usually preferred to have the rear wing far back, as the distance from the wing to the rear axle multiplies its its force on it.

You need to rethink that ;-)

Again; the leverage needs be compensated by more downforce at the front. That is not júst downforce. It is also air resistance.
Any negative lift cause by leverage at the rear = loss in the form of unneccessary drag.

The reason to put the wings further back are aerodynamic. And yes, that is a trade off between efficiency gained and loss because of less ideal geometry.

Fórce wise, the ideal is to have the force directly on the rear axle. That is how the first wings were mounted btw.
Porsche even mounted the wings on the middle! of the 550 spyder.

[Snelbaard]

You need to rethink that ;-)

I don't think I do. It goes without saying this is only desirable if adequately counter balanced by front axle downforce.

But again we are talking here about race car dynamics. Let's not kid ourselves, our cars are not race cars (mostly) and a wing like this will be mostly ornamental, wherever you place it.

One of the main reasons the first wings in F1 were mounted over the axles by the way is that they transferred force directly to the suspension arms, bypassing the springs. This way, suspension charactaristics remained unaffected by aerodynamic load, and the car's attitude would remain constant. quite clever!

[Petrus]

Of course I meant the Rear wing support location.

But let's be real here. I wrote 'most of the time' for a good reason. Most of the time you will not be going at such speeds that would make this effect problematic for our cars. Say you generate 50kgs of downforce, which I think is a generous estimate, you would theoretically cause a lift of 5 kg's on the front axle. Again, this is assuming the rear suspension is rigid, which it is not. Let's once again be generous and guess that 3 kg's of lift actually make it to the front axle. I wouldn't lose sleep over that.

The reverse rake this causes would indeed cause further aerodynamic lift, but I wouldn't be surprised if rear wings such as these would be accompanied by front dive planes to offset these effects.

I am aware that subtle changes can have pronounced consequences, but that does not make it true that every small change has such effects, especially at our relatively pedestrian speeds.

Although you are rather low with the 50 kilos, let´s not go there and go with 50 kilos.

Support it ´on´ the rear axle and it is just that; 50 kilos extra downforce at the rear and in total.
Support it only 24.5 cm behind the axkle and it becomes 50 rear, -5 at the front, 45 netto.

Now the effect of even ´only´ 50 kilo is significant.
My car with driver is say 1000 kilo.
Those 50 kilo add 5% extra cornering and braking or in other words 5% extra safety margin at the same speeds. That at a 1% weight penalty = 4% nett positive.
Do you know hw much extra power you need to go 5% quicker on the straight bit? Now thát is léss safety...

I kinda like 5% (4) extra safety margin ;-)


The generalisation of aero oly being effected at high speeds is partly correct.
It gets more correct the heavier the car is.
The MR2 Spyder is a fairly líght car and from about 80 km/h the aero becomes a factor with enough force to have effect.
Again, that ´silly´ small ducktail on the back op an Audi TT  was added to stop mortal accidents and it wórked!! Go figure.


p.s. did you watch the youtube I linked.
If you did I have a nice one with/without on track on an MX.

[Petrus]

Positive oopsie.

Had the above illustrated big one in ebay watchlist and they lowered the price significantly with a make an offer option. So I made an offer and it was accepted automatically. Paid so it should shortly be flying thisaway. Oh my 

[SuperArt]

TTE turbo run with following configurations:

No spoiler
TTE boomerang only
TTE boomerang + GB ducktail
GB ducktail only


No appreciable difference.

Most noticeable difference to handling was in changing tyres from Bridgestones to Yokos to Toyos. Also changing switching between light wheels and heavy wheels. Maximising mechanical grip trumps any aero advantage gained from altering the body.

These cars are not about aerodynamics, you need to have changed many suspension components and perhaps souped up the power a little before aero is of any concern.

Our cars have a CoD of 0.353 which is worse than a lot of run of the mill big saloons and grocery getter hatches.

[shnazzle]

Could it be suspension-dependent?

I sold my TTE banana and found it a bit more unsettled at speed. 
I added a JDL ducktail and it changed next to nothing. Which leads me to believe the TTE banana does do something but the ducktail not so much

[Petrus]

The bad CoD is mainly because of the shape and a very strong argument in fávour of aero mods.
The shape is in effect an inverted wing! The air above needing to travel way further, thus faster than the air underneath.
The two worst bits are the short bubble cabin and the round bum. Additionally to adding a lot of travel, both create a lot of turbulence.

Secondly the Spyder is a relatively lightweight car which means that aero forces have relatively more weight.

Bottom line is that the bad shape of our Spyder makes it easy to achieve aero gains and secondly those gains have more effect becasue it is a light car.

The ducktail addresses the rounded bum. See Audi TT. It should increase stability at highway speeds and plus.
It creates a tear off ridge at the back reducing turbulence, with the effect resulting in less lift.
I have a way smaller lip and one notable effect is that the same amount of turbulence behind the windscreen when top down shifts 10-15 km/h upwards.
Ány lip at the back creating a tear off point is like the feathers of an arrow. Ok, a big fat heavy arrow and minute feathers, but in effect the same.

The banana sits rather close to the bubble, either hardtop or softtop. This is a low pressure area so the spoiler cannot do all thát much BUT it is also a high turbulence area and it would reduce this turbulence and reduce drag. A bit like the ducktail but less to the back.
Top down it should do a lot more to reduce turbulence.

I have added a small rubber ´dam´ under the front bumper. Splitter is a bit too much of a word for it but is does work in reducing the pressure under the car = reduce the lift effect of the inverted wing shape of the car.

I also vented the bonnet. This diverts air that would otherwise flow under the car to flow above it. Again counteracting the inverted wing effect.

The lip already mentioned. It adds a Kamm edge effect to the aerodynamically bad round bum.
The large wing was in the back of my mind when I choose this lip. It increases the efficiency of the big wing by increasing the air flow under the wing.

Then we get to the nappy. With the OEM catalist fitted, the nappy minimises turbulence and thus both drag and lift.
With no cat of a sinificantly smaller one, deleting the nappy creates a space under the rear* .
While this increases turbulence, it creates a low pressure area of greater importance, reducing lift at the rear.
Adding a diffuser would reduce the turbulence at the rear even more. The one I mounted is way too small but will still have sóme effect by creating mini vortices** and providing a tear off lip.

* a rear bumper delete at one time was an almost popular aero mod in budget racing.
I am sure there will be explanations of youtube.

** vortex generators at the back of the hard top will have a relatively large effect again because the shape is so bad and the car not a heavyweight.


The SBW is a different kettle of fish: It is a 145 by 21 = 3000 cm2 wing surface. That is a fairly large rc airplane and secondly it is more agressively shaped than rc wings because there is way more power to push them through the air..
Those 3000 cm2 mean that only 1 gramm of pressure difference multiplies already to 3 kilo!
You guys say you notice the balance change of the frunk emptied of spare/tools/wheel bucket and I totally agree. Now... at some 60 km/h the rear wing is pushing down with 30 kilos.

Have a look at https://www.youtube.com/watch?v=cUisEoS3VUg and keep in mind that the Spyder has worse aero and is lighter = more effect.

[Petrus]

A computer calculated model for the airflow over th Spyder ´bubble´:




It also illustrates that the amgle of attach of a rear wing needs be adjusted to the direction of the airflow, not the horizontal.

[Petrus]

[Petrus]

One of the ugliest wings ever, maybe even the car.

Nevertheless it has a Cw of 0.28 ánd included in this, the wing has a triple beneficial effect: It redúces drag while creating downforce and reducing the jaw moment.

You do put you finger on the why of the Spyder´s 0.35 (or .38 even, depending on the source): Looks.
Toyota´s aero engineers had a very stringent design brief;  avoid looks having aero induced íssues.
In a car like this, looks sell, Cw values do not.
Also, the thing is meant to be a mainstream runabout; a competitor to the MX, not Porsche competition so lift/downforce was limited to not being a safety issue.

We can see it too in the FL rubber strip under the front bumper. That is a basically invisible lift reducing mod.
Nóóó attention drawn to is and no mention whatsover that it would improve the PFL too. Nevertheless it does.

Btw. Í happen to think the Superbirds só cool. If I would have the chance/choice I´d drive it as daily wheels over any, ány, ÁNY other american muscle car from that era. With the roadrunner decal ofcourse :-)