Body and under body mods for a Track Spec Hatch

[fivebob]

there is no use having a front dam and splitter if the air can fill the low pressure void from coming in from the sides.

That's a very confident claim about a subject so complex as airflow and pressure differentials. Have you got any proof to back it up?

[gtpornstar]

Thanks for the responses guys, certainly a lot of info there.

Barry - Rear is fixed unfortunately so either i should look at making some custom shiz up or start bending that bar

Yeah am thinking about getting that sussed, btw you txt the wrong number earlier Will pm ya for the calipers your talking about.

hmm spring rates, yeah i should really check what standard teins are for this car.

I have removed the front engine under cover, thinking of making the front splitter and covering it all up again. then also thinking i need to let some
air up the back of the bonnet to relieve some pressure in the engine bay and also get more air flowing over the car than under.
Also thinking i need to look more closely on what air i am letting through the front bumper, before anyone says yeah shams you need
to fix that shocking bumper .... i know i am working on a little lip to put onto a replacement bumper.

Oh and btw Brent 2qik atleast has a factory rear spoiler

Rear difussers, theres things that just seem to channel air and some dig deep into the air stream, whereas others seem to try force air to the middle of the car.
What achieves what ?
here is an example of what i am talking about. -

http://i135.photobucket.com/albums/q135 ... 850335.jpg

http://www.pennon.com/products/diffuser ... P03_4T.jpg


I think looking at single seaters and f1 cars will probably not help and most likely confuse everything when it comes to a rear wing as the rear of a hatchback
has air doing some funky stuff


fxgt - hey bud your the 3sgte that was at the gtr day right ?
that rear spoiler, i think from what i have read is to reduce drag you really want to get a spoiler with a bow that allows are to travel faster over the top of the spoiler
or significantly more than the bottom in order to create a vacuum/pull. I think you will find that the rear spoiler you have will give you better downforce in the rear
but also will give you a lot of drag.
I dig your front splitter though as thats what i am looking to do except i may go back a little more (maybe in a second section) to close of the engine bay.
A front splitter that protrudes out will create an air dam/ grabbing air and forcing it to go straight through the bumper or over the car. This is what i think gived you the front
downforce.

cat007 - yup agreed, which is why i am not just jumping into it, i want to try gather some info.

Mr Revhead - yup there is but not specifically on the rear of a hatch back which is probably where most of my dilema is, what to try first in terms of a wing.
eg i would have thought there was more info or atleast pictures of wing designs for the mini coopers.

Molex - yeah i hear you and a lot of the under tray works seems to come into play there, yup will hit you up sometime to come have a yarn.

Malcolm - yup exactly my point. Good to know about the side skirts because i didnt really want to mess much with that, maybe just a diflector for the rear wheels.
I am not sure i will get far reading a book haha i will probably loose it after the 10th page Dont get me wrong i dont mind doing testing etc to see what works
and spend the time doing so, just cant really see myself reading much

btw is there a wind tunnel that belongs to the university of auckland ?

Thanks a lot guys, appreciate all the input. Some of the responses i have above i am only making assumptions so if im wrong dont jump down my throat

[gtpornstar]

I started typing this but realised i hadnt sent it and in the meantime Frost had responded so appogies for the double up.

Frost - not sure about the comment about why open wheelers dont need side skirts but production cars do?

Does the low pressure under the car make the car act like a wing in itself ? creating a downforce ?
Yes somewhere i read not to go over 7-9 degrees elevation
Diflection on suspension parts, something like the front of a ship to get air flowing fast around it ?

'more downforce then any foilwing will' You mean directing air away from the beam ?

[cat007]

If you happen to make a completely flat splitter, undertray and then diffuser - just make sure you leave room above the diffuser for the air that's passed between the undertray and the bottom of the car, following the gearbox tunnel etc, to get out.

Like the F430 for example:

[fxgt race]

No my car wasn't at the gtr day, I'm only a 1600. The rear spoiler was bigger and was to much drag so this is the smaller one, it is made out of .9mm ali and bends down at high speed. In our racing rules our front splitter is not aloud to go past the front axles. I do alot of testing and this set up is working for me.

[frost]

there is no use having a front dam and splitter if the air can fill the low pressure void from coming in from the sides.

That's a very confident claim about a subject so complex as airflow and pressure differentials. Have you got any proof to back it up?

no i dont have proof, pure speculation and remembering from back when i was interested in doing some undertray and diffuser. all was for a ae86 liftback. i dont know his car but i hope everything i type is taken as general basics and theory.

the point of having the dam is to limit the air from going under car and limiting stagnation causing drag. if there is not skirting then from the front wheels back would lose its low pressure and let air "hang" off undercarriage protrusions.
so if there is a side "hole" for the pressure to equalize.
the front would sag and the back would lift.

[gtpornstar]

fxgt race - oh ok must have been someone else, this is feb 1st at taupo track 1 im talking about just in case you didnt know who the organiser was


frost - For the sides can i just use a sheet like what looks to be done on the yellow civic on the first page ?
Also at some point there must be more of a restriction of the dam in front than it is helping in terms of limiting air underneath ? Meaning if it is not assisted up and over the car that is.

[fivebob]

the point of having the dam is to limit the air from going under car and limiting stagnation causing drag.

That sentence doesn't make sense to me, surely the air dam causes a stagnation point to form in front of it, or are you referring to something else?

if there is not skirting then from the front wheels back would lose its low pressure and let air "hang" off undercarriage protrusions.
so if there is a side "hole" for the pressure to equalize.
the front would sag and the back would lift.

I've had an interest in aerodynamics for the best part of 40 years, studied vehicle aerodynamics for the last 20 or so, and have a fairly good library on the subject, even I wouldn't be so bold as to make statements like that.

When it comes to how air behaves you shouldn't make assumptions on how you think it will behave, that just leads to false ideas about what will happen. Which very often is the opposite of what actually does occur.

Aerodynamics is less about theorising what will happen, and more about observing what does happen then building theories to fit the results.

[frost]

my wording of the sentences is probably not the best way to put forth what i want to say.

yes that is how i understand the effect of the dam, causing stagnation in front and leaving the only path for it to go is over and to the sides. and some to enter the radiator entrance of cause.

from what i remember the drag created is only parcel/momentary ??
the overall reduction of drag by stagnation under car would out weigh the drag created by the front airdam, i am to believe.

these where theory's and models i was reading and about to implement but never got the time or space to do so. however i do intend to pick up where i left off and do some

one thing i notice is that newer cars have very small inlets for radiator air flow. some times just a slither of gap(FLA). and also a very integrated and sealed engine bay undertray design, leaving me to think that low pressure creation in some key areas would help cooling more effective. i am liken to the idea of too much air flow is not always best. i cant remember what thats called.

[fivebob]

one thing i notice is that newer cars have very small inlets for radiator air flow. some times just a slither of gap(FLA). and also a very integrated and sealed engine bay undertray design, leaving me to think that low pressure creation in some key areas would help cooling more effective. i am liken to the idea of too much air flow is not always best. i cant remember what thats called.

That's not so much about increasing cooling system efficiency as it is about reducing cooling system drag. Some racing aircraft have gone so far down the line of drag reduction as to create cooling system thrust.

I would suggest you find a copy of Aerodynamics Of Road Vehicles or Road Vehicle Aerodynamic Design and study them before you get too far down the track of forming your own (erroneous) theories

[frost]

cooling system thrust sounds very interesting

i actually orded the second edition introduction by r h barnard and a book by Joseph Katz but have not seen them in over 4 years, maybe i should find them and refresh myself.

[RH9]

You guys havent been under any late model Jap or German cars like a BMW 335 twin turbo, M3, R35 GTR, 911 turbo??

I can tell you first hand that they ALL have flat underbodys thanks to clever floor pan layout and undertrays.........massive fuel efficiency improvements due to LESS drag and more downforce/suction.

Leave it to the experts (ie the manufacturers) and then just copy their R&D

[frost]

yes i have good access to Ferrari 599, porch gt3, 99 nsx, rx8 evoX my bmw 7 series. r35 gtr, Lamborghini gallardo, some Maserati thing im not sure about,
even the Suzuki areo has a pretty good underbody design,

[cat007]

Dare I suggest that a prius probably has a flat underbody as well. Keeping with the rest of the cars streamlined nature

cheers

hunt

(hunt and associates do not condon the use of prius' in any circumstance. In the unlikely event that the prius is used as a benchmark, hunt and associates remain impartial)

[gtpornstar]

Leave it to the experts (ie the manufacturers) and then just copy their R&D

Hey ANdy, fancy meeting you here. I suppose its for the aristo

Ok from the reading ive been doing i think i am somewhat sussed for the front and under body but just need to think about what i am dong for a rear wing.
Was leaning towards something like this - Just need to check how easy it is to get into the rear