Vented bonnet & rear spoiler

[Petrus]

Got some more things to complete before I take on more but informing oneself is like the primer and prep. of a spray job.

Over the yeras I have added ´bonnet vent/scoop´ to several cars. Always to lower underhood temp. Sometime by scooping air ín, sometimes by a vent in a low pressure area to get it oút.

In the case of the MR it is different. Although it may aid air flow through the rads. my first priority is try get less lift.
What have you lot done and with what effect?

A rear spoiler... well, it will not be of much use for extra traction up here on the mountain roads and on the highway mainly be a drag costing fuel and adding a bit of directional stabilty.
The TTE and other small ones hugging the rear deck are harmless but I don´t like them.
So that leaves the big ones. So ugly they get their own charm. Almost. It does add a bit bad ass, literally, to the rather sweet looking SW30.
Again, what have you done and how did it pan out?

[shnazzle]

Not seen anybody do anything to the bonnet for down force. Cannards and splitters yes. And flat floor.

Rear wings; I felt that the TTE " banana" that sits nearer the rear window actually did something. But the ducktails like myself and Helen have are just for decoration. Granted I think they look mighty good.

Big wings that stick out over the top of the roof is the way forward for the track boys. But not so acceptable for road use. I get enough ridicule on the roads from white van men as it is. Especially when I'm blasting ABBA for some reason.

[Petrus]

The bonnet vents shoúld imo relief the pressure build up underneath the front. With the standard set up all air scooped up is forced to leave under the car where there already is a high pressure area.
Small vents will not do a lót but even 20-30 kilos less lift is about as much as one can hope for with a splitter that does not look like a cake scoop.
I was calculating the effect of a neat looking splitter and concluded that cutting a hole would be more effective than adding a meter and a half of plastic. A vent would give just that extra bit of cooling too I thínk.

Yes, a rear wing would draw loks but I don´t care about those. You should see how much attention the vines with flowers and butterfies in pink/lavender on mountain love´s car get. She also has pink/purple LEDs under the sidesteps making the underside glow in the dark!! I would need to fit flame throwers under the rear wing to get that level of attention 
I would be looking at a wing below the roof line though. Wing proper inverted wing profile. Even horizontal it should provide downforce and enough drag to give the car a stabelising tail.
Btw. does your periodic inspection frown on it or??

[shnazzle]

The bonnet vents shoúld imo relief the pressure build up underneath the front. With the standard set up all air scooped up is forced to leave under the car where there already is a high pressure area.
Small vents will not do a lót but even 20-30 kilos less lift is about as much as one can hope for with a splitter that does not look like a cake scoop.
I was calculating the effect of a neat looking splitter and concluded that cutting a hole would be more effective than adding a meter and a half of plastic. A vent would give just that extra bit of cooling too I thínk.

Yes, a rear wing would draw loks but I don´t care about those. You should see how much attention the vines with flowers and butterfies in pink/lavender on mountain love´s car get. She also has pink/purple LEDs under the sidesteps making the underside glow in the dark!! I would need to fit flame throwers under the rear wing to get that level of attention 
I would be looking at a wing below the roof line though. Wing proper inverted wing profile. Even horizontal it should provide downforce and enough drag to give the car a stabelising tail.
Btw. does your periodic inspection frown on it or??

I was thinking that actually and I vaguely remembered @leethesparky (might not have been) having another spoiler to put on for MOT time.
Someone did anyway. But might not be the case

[Topdownman]

I have bonnet vents (with under bonnet plastic removed to allow the air to flow). My thinking was that it would increase flow past my radiator, reduce high speed lift and look pretty cool.

I also have a engine cover spoiler which looks pretty cool.

I couldnt honestly say I have been able to spot any difference as I didnt do a sample drive, fit the parts and redo the same drive in order to try to gauge the success or otherwise. I have no reason to think the vents arent doing what I expected though.

(They do both look pretty cool though, fact!).

[Petrus]

I have bonnet vents (with under bonnet plastic removed to allow the air to flow). My thinking was that it would increase flow past my radiator, reduce high speed lift and look pretty cool.

I also have a engine cover spoiler which looks pretty cool.

I couldnt honestly say I have been able to spot any difference as I didnt do a sample drive, fit the parts and redo the same drive in order to try to gauge the success or otherwise. I have no reason to think the vents arent doing what I expected though.

(They do both look pretty cool though, fact!).

Thank you very much for sharing.
Indeed the vanity plastic needs be removed as does the spare trunk.

Please show us how cool it looks!

[Nvy]

I have seen one of rogue cars have vents out of the hood. Also lee has one. After seeing a video the other day, im not sure that a wing would help us due to the car form. It has to be either rly high or rly wide or both to do anything.

[Petrus]

It has to be either rly high or rly wide or both to do anything.

Like;



This the Chaparral 2-E; basically the original which started it all.

[Petrus]

They were also the first to put the radiators in the side pods and use ducted vents in the bonnet to reduce lift/create downforce.
Ditto the ´canards´.

[Topdownman]

Thank you very much for sharing.
Indeed the vanity plastic needs be removed as does the spare trunk.

Please show us how cool it looks!

I didnt take my froot out, I need that space for storage!



There are some more pictures on my readers ride below.

[Petrus]

Thank you!

You opted for the ´Jaguar´type.
I would like slightly more flow. Not larger holes in the bonnet but more open inserts.

Ditto the rear spoiler. Your´s is probably one of the few if not only one that gives a better Ce by having less drag. I would like to spoil it all a bit more 
I will humbly bow to SpyderLee though; not going thát wild. Not thát high, nor wide and only lid mounted instead of properly low on the chassis. Caparral did it one better still though; axle mounted. Nobody goes thát extreme in F1 even!
Right, back to reality.
I will do the hood vents as allthough only tiny bits, it ís chucking metal 
Would lóve a big wing but... 6 kilos    Will need to think a bit more about that.

[Petrus]

Just put a tape measure over the rear spoiled of my son´s 340; 124 cm.

As such 110 cm. does not seem a lot on the wider MR 

[Nvy]

@Petrus Keep us updated, id like to do a wing too but have another idea. Once i clear my ideas up i will share them with you as it seems that you are a tinkerer and on my end once the design is done i can have these made for not so much cash. That would benefit all of us on this board of course not only me and you

[Petrus]

Sounds interesting Nvy. I am curious indeed.

Yesterday picked up the ´neon´ lights for under the side steps of mountain love´s car.

Will order bonnet vents in a moment.

So I have the camber bolts, the neon lights and the hood vents on the ´to do´ list.
The lightweight wheels are on it too but that is nothing much; just buy and pass the tyre shop. I would to have that sorted end of March.
Thus wing time will be here before spring time 

[Petrus]

For those who want a bit of fact based info:

https://scholarcommons.scu.edu/cgi/viewcontent.cgi?article=1000&context=mech_mstr

A quantified perspective is that 2 square feet of inverted wing spoiler suffiently raised above the deck, moderately angled to give a negative coëfficient of only 1, gives a 300 pound downforce at 42 mph aready.

The wing illustrated above is a bit smaller and would have that just under 50.

Angling it less would, solely because of the wing shape, stíll give a noticeable increase in down force at surprisingly low speeds ánd reduce drag up to legal highway speeds.

Obviously, a wider and/or broader wing would give more result still.

The neat thing with the MR2 is that it being light means that a moderate wing has a large % effect. I mean 15% extra downforce (without any centrifugal penalty) at the rear in a 50 mph corner is not to sneeze at.

[Petrus]

This illustration shows how a rear wing creates downforce while reducing drag





Meanwhile I will try a universal lip to create the effect studied by Wunibald Kamm. By providing a break of point the drag is significantly reduced.
The rounded rear of the MR2 is particularly suited for such a lip just like the Audi TT and that was indeed fitted with one off factory.
On the MR2 an added advantage is that it improves extraction of air from the engine compartment.






and lastly there is the Gurney flap which greatly increases a wing´s effectiveness. I will try explain it more when/if I go for a wing onto which wíll bolt one.

[shnazzle]

This illustration shows how a rear wing creates downforce while reducing drag





Meanwhile I will try a universal lip to create the effect studied by Wunibald Kamm. By providing a break of point the drag is significantly reduced.
The rounded rear of the MR2 is particularly suited for such a lip just like the Audi TT and that was indeed fitted with one off factory.
On the MR2 an added advantage is that it improves extraction of air from the engine compartment.






and lastly there is the Gurney flap which greatly increases a wing´s effectiveness. I will try explain it more when/if I go for a wing onto which wíll bolt one.

That's quite interesting actually. My ducktail spoiler is very similar to the TT spoiler and that was put on after the mk1 to reduce instability. So, it must do something!

[Petrus]

That's quite interesting actually. My ducktail spoiler is very similar to the TT spoiler and that was put on after the mk1 to reduce instability. So, it must do something!

Good point; although it redúces drag it incréases stability. You can really see it as the tail feathers of an arrow.
Have a look with you fingers on ´Kamm tail´ and you can find an explanation of the change in wake. Although there is more wake, it is more laminar as opposed to the turbulance caused by a lack of break off ridge.

The Kamm thingamies are not to be confused with the Gurney flaps. The latter is a ridge at the tail edge at the pressure side of a wing and it´s eddect is to keel the wing more ´filled´ and at the same time add a wake which in effect auments the wing effect.

Combining the three; Kamm tail ridge, inverted wing with Gurney flap, is aerodynamically very efficient/effective:






One word of caution:
You are aware that modifications can have effect on the balance of the car; on over- and or understeer.
Just venting the front, decreasing lift, will shift the balance to less understeer.
Just adding more downforce at the rear will shift the balance to less oversteer.

A Kamm thingamy has no effect on downforce so no effect on balance.

[Ozzy]

Anyone know what those arches are in the picture above? Or are they just some custom one offs?

[Petrus]

Not a clue but did find a neat wing with proper adjusting struts:

[105e]

Would love to fit a rear big wing like that, perhaps not quite so big,  but wouldnt dare be seen driving it unless i also fitted a big v8 with 500 bhp..

[Petrus]

but wouldnt dare be seen driving it unless i also fitted a big v8 with 500 bhp..

You are missing the point of lightness plus traction entírely; it is all about córnering speed.

The point of the aero gadgets on an MR is to create downforce on a light car. This results in more grip without any weight penalty.

Now you find yourself a V8 engined car, I will fit aero stuff and then we do a touge run here in the mountains 

[105e]

No i am not talking about beating anyone in a race,  i just like those spoilers, for the look, but unless i had something to back it up, as in big bhp i would feel a bit stupid..

[Petrus]

but unless i had something to back it up, as in big bhp i would feel a bit stupid..

You stíll miss the point.
The things you need to back it up are nót horses but cornering skills/balls.

Have look at the Spirit MR-S beating the BMW M3 E92 V8.  Yes, V8 and tuned a bit so most likely those 500 hp.ç

A long time ago I had an lp record album with winged balls on the front cover  :notworthy: Think it was the Allman bros.

Edit:  yessss it was https://feedtim.files.wordpress.com/2012/10/p10108071.jpg

[105e]

I am not missing any point, i am not interested in making my car lighter/more aerodynamic or racing, (although i would like a quicker 0 to 100 time) but i think driving down the road, not a race track, with a wing like that on the back in a standard mr2 would make me look like a right wally.. and i will say no more as i am getting away from the point..