The Aero thread

[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.

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

Will try and get a photo uploaded, there doesn't seem to be an option on this forum, they are actually just cheap Ebay special vortex generators! Genuinely amazed they actually did anything, guess they are just simple to make.

[Snelbaard]

I always liked these diffusers, made by Rcyntype of Spyderchat. If not functional, it does look the business.

[m1tch]

I always liked these diffusers, made by Rcyntype of Spyderchat. If not functional, it does look the business.

I agree that they do look good, however to be of any use they would need to be fairly large and extend out the back of the car. I am currently just looking for smaller functional aero parts that work ok on a road car.

[Petrus]

I agree that they do look good, however to be of any use they would need to be fairly large and extend out the back of the car. I am currently just looking for smaller functional aero parts that work ok on a road car.

A short one works just like the vortex thingamies and any such diffuser helps reducing rear lift and turbulence however little.

[m1tch]

I agree that they do look good, however to be of any use they would need to be fairly large and extend out the back of the car. I am currently just looking for smaller functional aero parts that work ok on a road car.

A short one works just like the vortex thingamies and any such diffuser helps reducing rear lift and turbulence however little.

I will be looking into options, but for improvements I will be looking mainly at fitting a basic front splitter/rubber lip initially and concentrate on sorting out a flat floor with the under bracing.

Will try and get a photo added, not sure if the below works from the Facebook group:

[m1tch]

Hmm trying Imgur:

[Petrus]

Thank you Mitch; appreciate the effort.

The ´diffuser´ I have has akin fins; less (5) but longer and higher, euh... lower. Still not fitted it because of faffing with the exhaust system.

[Petrus]

Almost half a year later....

Am awed by the positive effects of the aero mods.
The additional weight is about as much as the cost; very little. The effect however is disproportionate. Just think Mongos.

I now have, in chronological order; the bonnet vents, a lip behind the engine deck,  a lip under the front bumper skirt, rear ´splitter´ and a large wing.

The bonnet vents lower the pressure under the bonnet, reducing front lift.

With the front more stable, the rear felt less to. Note ´felt´ as it is relative; ofcourse it was as before.
Now the rear ís a bit of a weak aspect as the round bum gives a lot of turbulence. It does not make the car stable persé but does give a lot of impression of instabilty because it the movement is félt.
The small rubber lip made a noticeable difference. It even was felt in less turbulence over the windscreen with the top down. Not a lot but real.

So back to the front again as the simple rubber rear lip made a notable effect. Thus a simple rubber front lip fitted and yes it reduces flow under the car, reducing front lift further.

When I fit the decat downpip, deleted the nappy too and fitted the splitterlikethingamy. I did not notice anything but it shoúld decrease rear lift, even if not enough to feel.

Now the biggy. The rear wing.
I fitted it relativey far forward to minimise a lever effect and also vertically matched the trailing edges of the lip and wing.
The effect is AWESOME. From 60 km/h the car starts to feel more planted at the rear. At illegal speeds through highway curves it feels like a longer, heavier car. At illegal speed passing a large lorry with in strong side wind from the lorry side, the car remains róck stable.
No wind noise.
Oddly enough no noticeable effect in buffeting the cabin with the roof down untill véry much illegal speeds when it is a lot less.

All in all the front reduction of lift is like adding an arrow head whereas the rear wing is like adding the feathers.
I knéw the effects would be worthwhile but I am still positively surprised.

[tom256]

Aero simulation:


https://www.youtube.com/watch?v=vB1iAnpuHR4

[Petrus]

Thanks for sharing Tom.

[tom256]

Check this:
It the same guy from MR2 aero video:

https://www.youtube.com/watch?v=rDN9LGtOF74

https://www.youtube.com/watch?v=tlG0QMhfD24

[m1tch]

Aero simulation:


https://www.youtube.com/watch?v=vB1iAnpuHR4

Thanks for that, I knew there was a separation bubble back there

[Petrus]

Thanks for that, I knew there was a separation bubble back there

The lip helps, the wing even more and adds negative lift, the lip with the wing makes the latter more efficient.

[shnazzle]

Thanks for that, I knew there was a separation bubble back there

The lip helps, the wing even more and adds negative lift, the lip with the wing makes the latter more efficient.

Seem to be seeing this a lot more on the track cars. 

Usually it was either a wing or a spoiler. Now it's both to some degree. 

One post said that a guy added the spoiler lip to allow for a less steep angle on the wing to decrease drag from the wing.
Quite clever I guess. Whether it works I don't know.

[Petrus]

One post said that a guy added the spoiler lip to allow for a less steep angle on the wing to decrease drag from the wing.
Quite clever I guess. Whether it works I don't know.

I do.
Have explained it here earlier.
The crux:
The wing is an inverted airfoil: Speed differential causes pressure difference; faster under than above = force down.
The lip improved the flow between wing and deck = higher speed under wing = larger difference = more force down.

[shnazzle]

No I get how each works separately

Makes sense logically but how it actually looks in a windtunnel... Won't know until someone puts it in a windtunnel.

90% of the "mods" we do on this forum are scientifically unfounded anyway If anything it looks cool

[m1tch]

No I get how each works separately

Makes sense logically but how it actually looks in a windtunnel... Won't know until someone puts it in a windtunnel.

90% of the "mods" we do on this forum are scientifically unfounded anyway If anything it looks cool

I did a tuft test on mine, so technically in an outdoor wind tunnel

[Petrus]

No I get how each works separately

I just explained, or tried too, how it works in conjuction. And there áre flow tests on the internet, albeit at scale. These are why I went for it.

A very mice bonus it that it deminishes buffetting over 120/130 km/h with the hood down. You notice that when you accelerate at that speed léss air falls into the cabine behind the windscreen. Cool!

[FredyCro]

Almost half a year later....

Am awed by the positive effects of the aero mods.
The additional weight is about as much as the cost; very little. The effect however is disproportionate. Just think Mongos.

I now have, in chronological order; the bonnet vents, a lip behind the engine deck,  a lip under the front bumper skirt, rear ´splitter´ and a large wing.

The bonnet vents lower the pressure under the bonnet, reducing front lift.

With the front more stable, the rear felt less to. Note ´felt´ as it is relative; ofcourse it was as before.
Now the rear ís a bit of a weak aspect as the round bum gives a lot of turbulence. It does not make the car stable persé but does give a lot of impression of instabilty because it the movement is félt.
The small rubber lip made a noticeable difference. It even was felt in less turbulence over the windscreen with the top down. Not a lot but real.

So back to the front again as the simple rubber rear lip made a notable effect. Thus a simple rubber front lip fitted and yes it reduces flow under the car, reducing front lift further.

When I fit the decat downpip, deleted the nappy too and fitted the splitterlikethingamy. I did not notice anything but it shoúld decrease rear lift, even if not enough to feel.

Now the biggy. The rear wing.
I fitted it relativey far forward to minimise a lever effect and also vertically matched the trailing edges of the lip and wing.
The effect is AWESOME. From 60 km/h the car starts to feel more planted at the rear. At illegal speeds through highway curves it feels like a longer, heavier car. At illegal speed passing a large lorry with in strong side wind from the lorry side, the car remains róck stable.
No wind noise.
Oddly enough no noticeable effect in buffeting the cabin with the roof down untill véry much illegal speeds when it is a lot less.

All in all the front reduction of lift is like adding an arrow head whereas the rear wing is like adding the feathers.
I knéw the effects would be worthwhile but I am still positively surprised.

Wow great work!

Is there a build topic on this forum, I would love to see in pictures what exactly was done? This would help me in my build too very much.

[Ardent]

Search for the belle thread by petrus.

[Gaz2405]

Interesting thread this, for the time being I'm going to go with:

Front splitter, vented bonnet and Rear wing with duck tail still on. Also got large rear bumper cut.

Flat bottom is next on the cards, but going to coincide it with rear diffuser and re worked exhaust.