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Keyboard 'worrier'
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Ok if your serious about aero mods, then get reading, loads of stuff on clubroadster and miataturbo sites about all this. I'll tell you how I understand it all.
For a start it wouldn't generate downforce, it would reduce lift and increases drag.
Spoilers work best to improve airflow under the car in conjunction with rear diffusers and flat undertrays, which need Sideskirts and front splitters/airdams. A spoiler is a peice in a large puzzle, and with regard to effecting lap times in such a way that you would notice would be fairly hard to measure in a controlled way.
I'm happy to be proven wrong but I doubt that's any hard data from any tracks, but saying that I do know hardtops are proven to reduce lap times round the nurburgring due reducing drag.
Much better off getting a front splitter or airdam as they are proven to improve lap times on track.
You can't expect to just stick on a spoiler and marvel at how its transformed the car, the standard car has so many areas to improve from the big wing mirrors to the parachute like rear bumper, but every change effects how the airflow is to the next part, for example, people who have lightened their bonnets by cutting off the strengthening under them have seen how much the bonnet is being flexed by the poor airflow thru the engine bay and so high under bonnet pressures, so some vents and that improves that, then sealing the sides of the radiator to improve airflow thru that, radiator slam panel for example.

Its a very deep subject aero that's for sure, and unless things are proven in a wind tunnel you can't be really sure how its truly effecting anything.
 

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The common consensus is they are purely for looks due to the hideous flow characteristics caused by the hardtop/soft top. They *should* be functional if you can get the flow to stay attached down the rear screen, proven successfully by sticking vortex generators to hardtops or getting a 'fast back' hardtop.
 

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Spinning around
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Discussion Starter · #4 ·
I realise I could be opening a whole can of aero worms here but I am just exploring ways of reducing lap times without touching the engine.

I do have a front splitter and the parachute rear bumper will be dealt with next week.

Thanks for the comments though - I will be doing some reading up I think!
 

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I realise I could be opening a whole can of aero worms here but I am just exploring ways of reducing lap times without touching the engine.

I do have a front splitter and the parachute rear bumper will be dealt with next week.

Thanks for the comments though - I will be doing some reading up I think!
Go on a diet....
 

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Unsurprisingly I've looked into a lot... here's what I've found:

A rear spoiler absolutely can create downforce, it can also reduce lift or drag... it all depends where its placed, at what angle and how high it is, and whether you have a soft top (and whether it is up or down) or a hard top.

First lets start with the top. Soft tops are not great as they are not a smooth shape and mess up the airflow over the car. With a soft top up, or down, you'll need the spoiler to be approx 10 inches high or more to be in clean air. Thats not to say it can't have an effect if its lower down, but it will be hugely reduced. That only counts for the centre of the car though, the air will still be smoother towards the sides of the car so if a spoiler goes to the edge of the car it will have an effect whether high up or low down.
With a hard top the airflow is a bit smoother, so the spoiler won't have to be so high, or go so wide to have an effect.

From what I can gather, the ducktails like mine that are low at the sides and high in the centre only will have a minimal effect on downforce, they do however seem to help overall stability at speed. Ideally if its a ducktail you want then for the maximum effect you'd want it to be styled more like the YSCC one... although not as steep an angle, and ideally a bit taller as well. The bit of the ducktail that will be doing the work is the bit towards the edge, and it will only be a small amount of work.

As to speeds, you won't notice much if anything at any legal speeds, its more 80+ that they have an effect.... above 100mph the effects are a bit more noticeable, but how often do you get there, even on track?

Bear in mind that compared to a BGW, they don't do much at all to be honest, but I can very easily notice the difference when I use a plain bootlid on my car at motorway speeds. By way of comparison, a well placed BGW such as the one on the Garage Hundred One car has been measured to produce 110kg of downforce at (I think) 70mph.

Russell.
 

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Thanks Russell, I thought you would have looked into this!

How does the analysis change if you have no hardtop and no softtop?

I agree speeds in excess of 100mph are infrequent but I would say 80mph+ is fairly common.
Thats the worst option of them all, the air flow can be a real mess as it is forced quickly up over the windscreen, then stalls as it goes into the cabin and then tries to find a way out. In reality its how most of us run most of the time though. Ideally you have a toneau cover with a small hole for you... although a Roll Bar can make that nigh on impossible.

Russell.
 

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regardless of function, I just think they look sweeeeeeeeeeeeeeeeeet
 

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Strip the crap out of it! Reducing weight is just the ticket for track use. A good geo set up will probably reduce track times the most per £.
 

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i think it is worth considering aero, but just don't go overboard on it. I'd concentrate on removing drag more than anything, so a flat undertray as much as possible, and making sure the rear bumper isn't a parachute!

After that, aiding stability is a good idea... so some sort of front lip spoiler, and some sort of rear spoiler. Whether it makes a big difference or not is hard to say, but my car is 100% stable at 125mph and I think at least some of that has to be down to the spoilers.

Russell.
 

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The Small One!
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Wouldn't it make more sense to concentrate on adding downforce (or rather reducing lift) considering a '5 is all about handling and not power?

Reducing drag is cool and everything, but when the car is going to top out at 130mph anyway isn't it better to be able to go around those corners a tad faster instead

Grip > Top Speed in a 5 IMO
 

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Look up the basics of aerodynamics, based on an aerofoil section, the more lift you have the greater the drag, reduce the drag reduce the lift, so rather than try to add downforce with wings first improve the basic shape of the car thru the air by letting any air that gets underneath get out as quickly as possible. Reducing the amount getting under there in the first place with a splitter or air dam, then you have things like reducing the turbulence and changing the separation point with rear diffusers which in turn help out rear spoilers. Its a big can o' worms when you start digging but if you try and not get bogged down there's areas to improve without having to worry too much.
 

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The Small One!
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Look up the basics of aerodynamics, based on an aerofoil section, the more lift you have the greater the drag, reduce the drag reduce the lift, so rather than try to add downforce with wings first improve the basic shape of the car thru the air by letting any air that gets underneath get out as quickly as possible. Reducing the amount getting under there in the first place with a splitter or air dam, then you have things like reducing the turbulence and changing the separation point with rear diffusers which in turn help out rear spoilers. Its a big can o' worms when you start digging but if you try and not get bogged down there's areas to improve without having to worry too much.
Agreed, a nice set up with a splitter/under tray/diffuser will give such a change to the way the car handles - that's the first step ill be looking to go when I find the time!
 

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PANDAfactory
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My ducktail is fitted for function > form. I'm under no illusion that it offers any aero benefit though. My choice in fitting it was to reduce weight. Mine's a single skin and allowed the lock, hinge etc to be gutted too. Had I the option of a lightweight boot without the ducktail I'd have chosen that instead.
 

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I realise I could be opening a whole can of aero worms here but I am just exploring ways of reducing lap times without touching the engine.

I do have a front splitter and the parachute rear bumper will be dealt with next week.

Thanks for the comments though - I will be doing some reading up I think!
Go on a diet....

[/quote]

Word...Unless you are dealing with high speeds, weight loss will show the biggest gains overall. The ducktail trunk is not a big downforce creator but it is a lift killer. And that means that it increases stability and predictability at speed.
In my lightweight, FWD, hatchback, the biggest single advantage I have over newer, faster and more expensive machines is the light weight. Find a way to lose some fat.
In a Miata, losing the obvious stuff like a spare tire, jack etc is easy, but the learning curve goes up steeply from there. Changing material is the most effective way to lose weight. And CarbonFiber is the material I'd recommend.
 

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