The Aero thread

[m1tch]

Hi all,

Just wanted to start an aero thread to try and pull together everyone's findings on what aero actually works - both on road and on track.

Just having a quick read up about front splitters,ideally they should be about twice as long as the ride height of the car to be effective.

I am also looking at the rear aero on the car, due to the angle from the rear window of the hard top, hardly any air is really hitting the engine lid, meaning that any spoilers on the rear aren't really very effective.

Currently I have no aero on the car, I am only wanting to add functional aero else it just adds weight, currently havn't really found anything that I would add to the car. The car is rear bias to adding more downforce onto the rear with a large spoiler wouldn't make sense.

[jvanzyl]

@lgriffiths is the one you want to talk to... it's his job for Williams!

[StuC]

You cannot view this attachment.


Was all excited for a moment there.

[Petrus]

Hi all,

Just wanted to start an aero thread to try and pull together everyone's findings on what aero actually works - both on road and on track.

Just having a quick read up about front splitters,ideally they should be about twice as long as the ride height of the car to be effective.

I am also looking at the rear aero on the car, due to the angle from the rear window of the hard top, hardly any air is really hitting the engine lid, meaning that any spoilers on the rear aren't really very effective.

Currently I have no aero on the car, I am only wanting to add functional aero else it just adds weight, currently havn't really found anything that I would add to the car. The car is rear bias to adding more downforce onto the rear with a large spoiler wouldn't make sense.

I opened several threads on the topic. Scientific material included.
The two rubber strips I decided on are light enough to be neglegible, are beer money and they both wórk.
You can find an example of the OEM front wubbah on how-to.
It reduces front lift.
The rear one is a mini version of the duck tail.
It works as a Kamm tail; providing a tear off edge, reducing turbulence considerably.

A rear wing does NOT make rear bias worse apart from the 6 or so kilo it weighs. A lighter abttery gains you twice that...
The downforce is not mass! It is weightless.
As such that force adds way more traction than centrifugal force = makes the car léss prone to loose traction at the rear at speed.
The crux is whether you need the extra traction. Even the bog standard 1ZZ has enough poke to push the car into the speed realm where the wing pushes down with force.
If I would be doing track days I would fit a wing in combo with the Kamm edge. The two make eachother more effective.
On mý use on the road it is overkill, only effective a few rides. Would still lóve to fit one as it totally fits with the fun theme of the car, but have too much headwind from the girls.
Thus still going for the other aero thing; headrest fairings. Those too reduce turbulence; see how effective the flip up thingamy is. Or the Mongos. Performance wise only marginally though unless you plan go top set speed records. In that case Mongos too and a cover over the empty passenger side so only a headrest fairing behind the driver :-)

Lastly there is the windscreen delete. In combo with a passenger side cover and a small scree in front of the driver it reduces the Cw ánd frontal area! And ... think of the WEIGHT!!!



Here an extreme Miata based version:

[m1tch]

Looking at the SuperGT GT300 MR-S cars, it seems that, apart from a widebody, they usually have smallish front dive planes, cut front wings, partly cut rear bumpers with a rear diffuser that doesn't extend and a a wing at hardtop height.

Example is the Apexi/ARTA car:

http://www.superstreetonline.com/features/toyota-mr2-spyder-arta-apexi-mrs-autobacs-racing/

Looking slightly closer at the car it seems that the rear of the hardtop has been modified to run at a slightly shallower angle.

[Petrus]

Those highly modded track racing cars are very limited as examples because the have hardly any wheel travel and no lift if not under pressure.

Also the wheel wells are vented.

The hard top shap is also about flow out of the cabin and the engine bay.

Just about the only aspects worthwhile are the combo of deck lid and wing which is 3D.

As I wrote, there are several threads with links. Do look those up.

All in all I´d say:
- try the two rubber strips
- vent the bonnet
- possibly a cheap 3D wing p.e. ebay 401489650528  ( I am STÍLL contemplating one....)

[thetyrant]

Unless you have a lot of extra power dont bother, plenty of grip with these cars if running good tyres and suspension so no need to slow it down on the straights with extra downforce it doesnt need

[m1tch]

Unless you have a lot of extra power dont bother, plenty of grip with these cars if running good tyres and suspension so no need to slow it down on the straights with extra downforce it doesnt need

Power output at full boost when everything is dialled in would be at around 400bhp, currently running stock NA at the moment but am looking at aero options I can add when the time comes.

[thetyrant]

Ah ok didnt know your were running that sort of power!, even so i would spend on tyres and suspension before aero!

[Petrus]

Ah ok didnt know your were running that sort of power!, even so i would spend on tyres and suspension before aero!

Point is that ´spend´ on aero is hardly existant (100 quid for 3D wing ánd the wubbahs) and the result is húge. Just stick a hand out of the window at 50 or 60 mph.
Concerning slowing down the effect is not horrible because most of the downforce comes from reduction in turbulence; in other words; you swap the parachute behind the tub/top pulling back for a wing on the heck pushing down.
If you would have the windscreen off, thén it would be very different because there would be no parachute behind the tub(top .
Even with standard output I would run a rear wing on track. I´d have in on the street if the virtual turbulence would not be so great.

[m1tch]

Ah ok didnt know your were running that sort of power!, even so i would spend on tyres and suspension before aero!

I won't really be running full power on the road, only at the drag strip, I am running a set of Silverstone Performance alloys so 7.5x17 up front and 8x17 on the rear - will look to run decent Yoko tyres (its why I had to bump up to 17s). Currently running Meister R coilovers at the moment and will be planning to run additional braces.

Will look to also run a flat floor (have seen some braces with additional metal to cover the underside, don't want to add anything that doesn't really do much. Saying that the car won't be above 70mph on the road so hardly any aero is going to work at that speed unless its massive.

@Petrus how do you mean about the 2 rubber strips? Do you mean running 2 rubber strips down the sides of the car like some of the F1 cars from the 80s?

[m1tch]

Ah ok didnt know your were running that sort of power!, even so i would spend on tyres and suspension before aero!

Point is that ´spend´ on aero is hardly existant (100 quid for 3D wing ánd the wubbahs) and the result is húge. Just stick a hand out of the window at 50 or 60 mph.
Concerning slowing down the effect is not horrible because most of the downforce comes from reduction in turbulence; in other words; you swap the parachute behind the tub/top pulling back for a wing on the heck pushing down.
Even with standard output I would run a rear wing on track. I´d have in on the street if the virtual turbulence would not be so great.

I am going to look at a few wing choices, was thinking to run a boot/engine lip spoiler if the airflow is running that low, perhaps some vortex generators on the back of the hard top to help flow. Ideally I would chassis mount the rear wing however the back edge of the engine lid and chassis are fairly solid and doesn't really bend.

[Petrus]

I am going to look at a few wing choices, was thinking to run a boot/engine lip spoiler if the airflow is running that low, perhaps some vortex generators on the back of the hard top to help flow. Ideally I would chassis mount the rear wing however the back edge of the engine lid and chassis are fairly solid and doesn't really bend.

Have a look at theebay one I listed.
Chassis mount is not really worth it on the MR2 Spyder:
The reason to mount it on the chassis is so the forces act on an as low possible point. The deck of the MR is already fairly low; about halfway the hight difference of say a BMW 3 series.

[Petrus]

@Petrus how do you mean about the 2 rubber strips? Do you mean running 2 rubber strips down the sides of the car like some of the F1 cars from the 80s?

The one under the front bumper and the Kamm lip.

[m1tch]

@Petrus how do you mean about the 2 rubber strips? Do you mean running 2 rubber strips down the sides of the car like some of the F1 cars from the 80s?

The one under the front bumper and the Kamm lip.

Ah I have some rubber strip for under the front bumper, Kamm lip being the same but for the rear?

[Petrus]

Ah I have some rubber strip for under the front bumper, Kamm lip being the same but for the rear?

Same rubber, different shape. See Belle´s thread. Put close up fotos of the profiles up.

[silversprint]

I have used a big wing, vented hood, splitter and diffuser.

The most noticeable was the big rear wing. Even without a hardtop or any other aero mods a proper rear wing is going to be noticeable at speeds about 60mph.

The next noticeable aero mod on my car was the vented hood.

I think because you can't lower the spyder enough without screwing up the suspension geometry the splitter and diffuser are hard to make work correctly. Also a proper diffuser would need to stickout at least 12inches past the rear bumper.

[m1tch]

Ah I have some rubber strip for under the front bumper, Kamm lip being the same but for the rear?

Same rubber, different shape. See Belle´s thread. Put close up fotos of the profiles up.

Just looked up the Kammback, our cars's don't have a flat rear so I think what you are trying to get at is fitting a boot lip spoiler on the rear boot lip? Basically a Gurney flap but without the larger spoiler attached to it.

[m1tch]

I have used a big wing, vented hood, splitter and diffuser.

The most noticeable was the big rear wing. Even without a hardtop or any other aero mods a proper rear wing is going to be noticeable at speeds about 60mph.

The next noticeable aero mod on my car was the vented hood.

I think because you can't lower the spyder enough without screwing up the suspension geometry the splitter and diffuser are hard to make work correctly. Also a proper diffuser would need to stickout at least 12inches past the rear bumper.

This is one of the photos I found when looking up MR2/MR-S aero online, basically go big or go home, I can't really run a rear diffuser big enough to make much difference for road speeds and still be able to park!

Might look at a large rear wing, will initially start with a few bits like a rear lip boot spoiler, front chin splitter and maybe vortex generators on just above the rear window. Might also look at a few of those hard top spoilers as well, would mean the downforce is being added right at the centre of the car.

[Petrus]

Just looked up the Kammback, our cars's don't have a flat rear so I think what you are trying to get at is fitting a boot lip spoiler on the rear boot lip? Basically a Gurney flap but without the larger spoiler attached to it.

Becaose the Spyder has a rounded rear, there is no break off pint for the air flow which already is rather turbulent because of the softtop/hardtop shape.

The Kamm rear designed to have the air separate with the minimum of turbulence, wake.
Putting a lip just behind the deck lid provides that; the separation ledge. The TTE ducktail is designed to do this and was offered as a cure for sensetivity to side winds and it works which is proof of the pudding.

The Gurney flap is something else entirely; slight hámpers the flow/separation and as such ´fills´ the wing area, resulting in slightly more pressure = more downforce.

As was observed, venting the bonnet is effective too: It deminishes pressure under the bonnet, improves flow through the rad. and lowers lift under the front. It noticably improves stability from about 60 mph.

Concerning the rear wing, the ´bubble´shape gives an odd flow pattern which in extrema is exactly where the ´3D´ wing shape was deigned for.
Lastly, the Kamm lip makes a rear wing surprisingly more effective because the flow under the wing is markedly better, less turbulent and as such the wake/drag is a lót less. By improving the air flow behind the top/car, the downforce comes at almost no price in air resistance.

Again; do read the threads I opened on this.

[m1tch]

I found the below Youtube video last night which shows flow over various car models, I have a 1:24 scale roadster model I will be building soon so will look to see if I can replicate the same sort of thing with our cars (the model also come with a hard top and soft top).

Looking at the Mk1 shape in the video with the angular front causing flow separation I am guessing that the Mk2 and Mk3 should have good flow until the back of the car, and as our cars aren't notch back the flow behind should be ok although there might be a detached flow bubble behind the rear of the hard top.

I will post up any finding of the tuft testing I am planning this weekend and will update the thread further once I have built up the 1:24 scale model as well.

[JB21]

Think I'm going to purchase both this rear lip and 3D wing for mine. Just need to find a front splitter of some kind.

I also need to source the OE undertrays as mine had neither fitted.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F401489650528


https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F273060739283

[m1tch]

Right, I have now managed to do some tuft testing on my car on the road, at 60mph there is a flow separation bubble across the whole of the rear - this is something I noticed when driving when the car was wet where everything apart from the very edge of the rear window was still wet.

I then fitted some individual vortex generators, 3" long, 1" from the edge of the window, couldn't fit all of them due to the contour on the hard top, however running 3 on each side and 2 in the centre I found that it did make a marked improved to the flow over the hard top.

I found that only the centre was showing flow separation, where I had the 3 vortex generators fitted on the sides I found that the flow was now stable down the back of the hard top. I am always sceptical of anything which is why I am testing everything before and after, only fitting aero that actually does something and this does seem to make quite a large difference.

This now means that there is more flow going down the back of the hard top meaning that there is now more flow going across the engine lid meaning that a boot lip splitter would now have some effect.

Silversprint - worth looking into fitting some to the rear of your hard top, was amazed at how much different the flow was, might make your rear wing more effective.

[JB21]

Right, I have now managed to do some tuft testing on my car on the road, at 60mph there is a flow separation bubble across the whole of the rear - this is something I noticed when driving when the car was wet where everything apart from the very edge of the rear window was still wet.

I then fitted some individual vortex generators, 3" long, 1" from the edge of the window, couldn't fit all of them due to the contour on the hard top, however running 3 on each side and 2 in the centre I found that it did make a marked improved to the flow over the hard top.

I found that only the centre was showing flow separation, where I had the 3 vortex generators fitted on the sides I found that the flow was now stable down the back of the hard top. I am always sceptical of anything which is why I am testing everything before and after, only fitting aero that actually does something and this does seem to make quite a large difference.

This now means that there is more flow going down the back of the hard top meaning that there is now more flow going across the engine lid meaning that a boot lip splitter would now have some effect.

Silversprint - worth looking into fitting some to the rear of your hard top, was amazed at how much different the flow was, might make your rear wing more effective.

Got a link to the vortex generators and pictures of where you fitted them?

[Petrus]

This now means that there is more flow going down the back of the hard top meaning that there is now more flow going across the engine lid meaning that a boot lip splitter would now have some effect.

The boot lip works anyhow as it provides a break off edge wheter the flow is somewhat lamnal or less to. Yes, it will be more effective with laminar flow.
A wing will have a considerable positive effect on the turbulence behind the top. Yes, vortex gens will still have a positive effect.
Sadly the little fins are limited to hardtop only. They do illustrate how effective aero mods are on the MR2 Spyder.