Underbody Aerodynamics

[NitroDann]

Hey guys,

Has anybody here put any serious effort into improving underbody aero through splitters or diffusers?

Im currently working on a rear diffuser for my NA and trying to research this area but not much can be found.
Im trying to decrease lift and get a similar effect to a big GT wing without having to put a big GT wing on my car.

Ive found some basic information to work with but nothing MX5 specific.

A couple of things I need ideas with is how to actually measure what has been achieved conclusively. I figure average ride height at a set speed would tell me what i want to know and the 'yarn technique' (using visual telltales on the car such as yarn to visually see airflow)will help me see where im making mistakes.

Anyone?

Cheers,
Dann

[broady]

There's a huge thread on miata.net - I don't have a link handy but a quick search should find it.

[NitroDann]

I found a couple, thanks heaps.

No one on here experimenting?

Dann

[Hellmun]

Different race classes to the US. Production sports doesn't let you touch Aero and the majority of race cars are in 2F that are on here.

[NitroDann]

Sure makes sense.

I so hillclimb my car and as such Im allowed to do pretty well what i please with it.

[lightyear]

How high are your speeds? I wouldn't imagine on a tight hillclimb there will be much advantage of aero. Remembering it all weighs a fair amount so that will slow you down.

[bruce]

There would be little or no benefit for the street or hillclimbs as the speeds aren't high enough. The extra weight may negate any benefit.

[de Bounce]

There would be little or no benefit for the street or hillclimbs as the speeds aren't high enough. The extra weight may negate any benefit.

Looks like someone made his race car into one giant wing at the 2010 National Hillclimb Championship

[lightyear]

Yes, that is a purpose built featherweight car. I have seen that car in person and it looks like a 2year old built it, but it does the job bloody well. On an underpowered mx5 you won't get to his speeds. But give it a go, put a flat undertray, floor and rear diffuser on and let us know how it goes.

Look here-http://www.timeattackforums.com/forums/aero-dynamics/2918-lots-aero-parts-built-my-garage.html

[NitroDann]

150 isnt fast enough to be worth it during a hillclimb?

The car will be doing circuit days soon and i figure at 100 when I stick my hand out the window it is a lot of force, a big ass wing has to help to some degree.

Besides, how good does proper aero look as opposed to big gay bodykits?

Thanks,
Dann

[philz]

NA- 0.38

Not that great, the same as the new Subaru forester

fyi-
mazda rx7 fd3s 0.29
mazda 6 0.27
toyota prius- 0.26

[16bit]

you need to take frontal area into account with drag coeficient

[Scoota]

I haven't tried any experimentation myslef, but I found some good reading at the AutoSpeed website. There are heaps of cool mx-5 specifiec experiments on this site, and lots of general ones too.

[url]AutoSpeed.com[/url]

[mr2 spyder]

I read somewhere that aerodynamics start to come into play at 80kmh. I am looking at setting my car up for hillclimb and normaly wouldnt make much difference but for the long Bulledelah or Mt Buller races it would be a smart move.

[NitroDann]

Soon Ill take my mould to a boat builder and have some diffusers made and tested for NA's. I just don't have the equipment or skill to mould diffusers to an acceptable finish or strength.

Trust me when I tell you that Bulladehla hillclimb is an uphill drag race with only a touch of the brakes in anything but a 500hp commodore running pushbike tyres. The Wooton Way (The road its held on) has some incredible sections but the hillclimb section is not one of them, it was originally used when fast cars didnt turn corners so back then it was exciting, not in any mx5 ressembling a weekend warrior under 250rwhp.
Aero would not be needed there.

Dann