240RS Maxi Aero Development

[driftstyre]

With the last track day of the year in a few weeks, the 240RS Maxi is recieving a bit of downforce to test out before next season. I was offered this used S14 Voltex wing for very very cheap and couldn't afford to let it pass (rent will have to wait). The rear diffuser will be made out of aluminum and the front splitter/air dam is thin birch wood sandwiched in carbon/kevlar. The undercarrige will be worked on this winter along with the straight cut dogbox.

http://www.dentsport.com/gallery/d/5539-2/DSCF2970.jpg
http://www.dentsport.com/gallery/d/5532-2/DSCF2967.jpg
http://www.dentsport.com/gallery/d/5536-2/DSCF2969.jpg

[yokotas13]

that shits sexy
end of story

[wootwoot]

I want to be your friend.

[d*star180]

Looks fucking awesome.

[Nachtmensch]

hotness. front shots?

[TipStylez]

Ever had someone try to put grocerys in the trunk, but end up finding a big hole? haha

Looks nice.

[Maximamike]

In the new shop, eh? Car looks great as usual! BTW, come down to F1 now we're running the bank as I type this.:)

[Igor]

that thing looks killer man, ya front shots would be cool, that shop looks nice to.

[ThatGuy]

If you want more pics and info on the car, just look at his other threads. :duh:
http://www.zilvia.net/f/showthread.php?t=95256
http://www.zilvia.net/f/showthread.php?t=107866
http://www.zilvia.net/f/showthread.php?t=110032

etc. etc. etc.

Or even better, click the links in his Signature to check out his shop.
http://www.dentsport.com/gallery/v/dsg/projects/bill240_001/

[SoSideways]

Can't wait to see the rear diffuser and the under carriage completed!

The front splitter is gonna be sexy too. Where are you getting the carbon/kevlar material to sandwich the birchwood from?

[punxva]

owwww i want to see the new front splitter :)

[A Spec Products]

Voltex is some expensive ass shit.

Glad to see you got a discount.

Its coming along very nicely.

[irritatedmax]

you are a baller...end of story. i have never seen someone put used goods to better use.

[corey240]

that s13 is awsome in person. i saw at gt live at vir. was wondering why there was no rear bumper.that thing was moving

[LB.Motoring]

Ever had someone try to put grocerys in the trunk, but end up finding a big hole? haha

Looks nice.


yah :hahano: becouse we all know this is the chassis to take to the grocery store?

such a grocery getter :duh:

lol, Looking good as usual Bill, damn that wing is so nice, /lick :keke:

keep it up!

[roorr0]

good luck with your project.

[driftstyre]

Mike,
Is the banking going to be in effect this weekend? Damn. I'll let Ramana know and we will head down. Though, that $100 can go towards the carbon to finish the diffuser/splitter. Dammit. How fast can the RM1s get up to with the full course?

I have one more event at Lime Rock which is a pretty high average speed course. I'm hoping I can make some changes through out the weekend to find some good settings (it will be the first event with sway bars and the dampening hasn't been touched yet). Supposedly MIT has a wind tunnel. Damn. If I could get a 1989 240 in a wind tunnel I would be famous.

[driftstyre]

Corey,
Did you or anyone you know take video of the Time Attack? I would love to find some exterior video of the car in action. Thanks.

[Dorifto89]

Bill...your car is hot sex in the third degree.

I wish I could come chill with you and the maxi. I'll bring my 125cc race kart and we can do hotlaps.

[corey240]

i mgiht have got a clip of the car doing a flyby. more or less the hole time i was there i was at the patriot course taping the timeattack and drifting. my wife was sick so we just stayed on the bleaches. i might have got some bits of it going by on the full course il check my video and see if i got anything. i might have cuz i wanted to get some. i really wanted to get some footage from the restraunt but it wasnt running when i was over there. it was so damn cold until sunday when the rain more or less stopped. il see if i got anything.

[driftstyre]

Thanks Dorifto. I wish you could hang with the Maxi as well. Its fun at the races when Nissan fans come over to check the car out. At a lot of the NHIS events there are a good deal of 280Z race cars, even an ex-Paul Newman car. The guys are all 50+ yr old Nissan finatics. They all seem to like the car but are not sure what its all about.

Corey, sorry about it not running. I missed 3 our of 4 of the SIM races and I really wanted to give people rides. One of the intercooler pipes popped off at 30 psi during the first sim race and I felt so bad for the kid who was in the car. Leaving the pits I took off through 2nd and 3rd gear (the kid was like "oh shit") and when it finally got traction at the top of third gear there was a giant bang and no power. I knew what it was immediately and limped back to the pits like a dog with a tail between its legs. I also underestimated how much fuel we would need and only brought 25 gallons. We used 35-40. And I ran out of money before the event even started. I wanted to make sure the car would last until the actual time attack so I could win some money and buy diesel for the way home.

The diesel for the trip was about $500, high coctane fuel was like 300. I think the truck (old mother hubbard) pulling 10,000 lbs gets better mileage than the Maxi:duh: actually they both suck.:faint:

[corey240]

this is all i got. the quality is bad for some reason, i dont know why cuz on the camera its perfect but its blurry and stuff when its on the comp. maybe you can edit it or somthing.

http://videos.streetfire.net/video/d4c357ac-620f-4e97-8434-986a0155bf0f.htm

[ThatGuy]

Damn! I want to see more exterior footage. Your car looked like it was flying Bill. Maybe it's the absence of a rear bumper that makes it look like an aircraft. Can't wait to see it with the spoiler and diffuser in place. MORE EXTERIOR FOOTAGE!

[Maximamike]

Mike,
Is the banking going to be in effect this weekend? Damn. I'll let Ramana know and we will head down. Though, that $100 can go towards the carbon to finish the diffuser/splitter. Dammit. How fast can the RM1s get up to with the full course?

I have one more event at Lime Rock which is a pretty high average speed course. I'm hoping I can make some changes through out the weekend to find some good settings (it will be the first event with sway bars and the dampening hasn't been touched yet). Supposedly MIT has a wind tunnel. Damn. If I could get a 1989 240 in a wind tunnel I would be famous.

I'm almost positive we will be using it this weekend as it went well this past weekend. Rotax's were going mid 70s down the back stretch so I'm sure the RM1's are a little higher. The ICC average speed was over 80 for a few Stars guys we had out there to give you an idea. I will find out for you and let you know for sure though.

When's the event at Lime Rock? Public? Last weekend at F1 for outdoor is next weekend so I should be free for a couple weeks.

[driftstyre]

Corey, That was sick. Damn. I've watched it like 10 times already. Thanks a lot for uploading it so fast.

Mike, the event at lime rock is on the 17/18th with COM and I think there is actually a drift event on the karting track as well. You should come out.

[DJPimpFlex]

The diesel for the trip was about $500, high coctane fuel was like 300. I think the truck (old mother hubbard) pulling 10,000 lbs gets better mileage than the Maxi actually they both suck.

TOTALLY feel you on that one. My van gets 8mpg on a good day towing.

[driftstyre]

"That Guy', the paint on your car is sick. It looks like a huey gunship or something. You need to mount a phalanx cannon on each side. What kind of wheels are those? Badass.

[corey240]

this is all the pics i got of your stuff cuz my camera battery died when i got over to your guys trucks. i was the one that told greg from nico where you guys were.
s14 engine bay...
http://i65.photobucket.com/albums/h225/corey240_photos/DCFC0239.jpg
s13...
http://i65.photobucket.com/albums/h225/corey240_photos/DCFC0238.jpg
sti...
http://i65.photobucket.com/albums/h225/corey240_photos/DCFC0237.jpg
by the way, the wing you had on the s13...did it have any beter functionality from being v shapped?

[ThatGuy]

Thanks Bill. The wheels are some cheezy knock-offs. Prime I believe. I got them for next to nothing, so they're good enough until I finish my 5-lug and install my Equips. The paint I did half jokingly. A dozen rattlecans of Krylon FTW! Hopefully by spring I'll be in a position where I can tear the car back down and put it all together the right way. :rawk:

[spdfreek0o]

What was used for the back glass on the s13?

[Full-Lock]

What was used for the back glass on the s13?

My -guess- would be plexiglass?

[corey240]

thatguy: were you in the drift event at gt live at vir? if not you have a double! il post up vid if its you.

[ThatGuy]

Definitely wasn't me. My car doesn't belong anywhere near a track right now. It would just be a big oily, smoking mess. :rofl: I wouldn't doubt I have a double. Krylon rattlecan's are CHEAP! If it doesn't have a Chargespeed hood with a POW/MIA emblem in the middle, it's not me. :bow:

[Walperstyle]

Very nice car. Purpose built. I'd do it like that if I coulf afford to race.

[CylonFrakker]

that car is the tits. I love the gusseted doors and the gutted under carriage. The meats that are on there and clean engine bay. that is what a track car should look like.

[SoSideways]

that car is the tits. I love the gusseted doors and the gutted under carriage. The meats that are on there and clean engine bay. that is what a track car should look like.

He ain't done yet man, wait till you see his carbon/kevlar front splitter and carbon (maybe C/K composite?) diffuser that's in the works right now put on the car :bigok:

[Maximamike]

Bill, full track with the bank will be used this weekend. Normal practice Saturday(9-1) and race Sunday. What kind of gas does the 240 use? Same stuff we have? I could probably give you a few gallons. VP 98 leaded.

[driftstyre]

Mike,
The 240 uses 109 Unleaded or better. I probably have enough gt plus here for the event this weekend. I think we filled the kart after the last race as well.

The molds for the rear diffuser pieces are complete and the completed part should be done by next week. I finally got around to putting some kind of bumper thing on there and it has more of a 240 silouette to it now. The diffuser should complete the rear end and eliminate my invisible parachute! Ducting for air exiting the radiator will be made this winter.
http://www.dentsport.com/gallery/d/5541-1/DSCF2996.JPG

http://www.dentsport.com/gallery/d/5543-1/DSCF2995.JPG

[ThatGuy]

This car never ceases to amaze me. Can't wait to see the diffusers. :rawk:

Keep up the good work Bill!

[DriftSpecial180]

Will you do S13 next?

[ThatGuy]

Will you do S13 next?

That is an S13. :duh: :loco:

[chmercer]

That is an S13. :duh: :loco:

correction. SYLAHLLLYLLLVBVIUAHHHHHH

[chmercer]

mr dentsport could you please explain what is going on with your fuel system

http://www.dentsport.com/gallery/d/2949-2/fuel_system.jpg

im very interested in proper fuel delivery setup but half of the time cars in USA are rigged up pretty poorly to where i doubt the saftey of the install, and all the nicley done japanese cars, well, cant get specs on thoes very well. im guessing the aluminum tank is surge, gold is pump, black is a filter, but i cant see too well

http://www.dentsport.com/gallery/d/2952-2/fuel_system2.jpg

on the actual installation of the cell, do you have any additional fire walls? it appears as though the bladder is inside the alum box you made. is that a legal mounting procedure? additionally are there any tie down straps or anything or is it just the lid holding it on.

LASTLY

do you fill it from inside the car or is there an external fill point that is not shown in the pictures. ive always been told that internal fill points can be a fire hazard from splashing fuel and such.

any insight you have on this (or additional pictures!) would be super great

[Ian]

There's an external fill point coming out of hte top of hte hatch area I believe


This car is pretty neat, I saw it at VIR




the green car in the VIR event was NOT That Guy...The cars look completely different.

[driftstyre]

The cell is an ATL FIA cell. The gold pump is a low pressure, hi flow feed pump for the surge tank and the blackish one is the high pressure pump from the surge tank to the fuel rail. There is a fram external fuel filter after the high pressure pump that you can't see. The whole lower part of the cell is mounted to the chassis and there are tie downs going through the shell, holding the cell down.

[CarloSR]

Bill, just awesome :bigok:

Got a question, what rad/cap/fans/ic/thermostat/coolant mixture are you running ? I don't push that kind of PSI but I live in the Caribbean and heat is a strong factor in a 100% humidity track.

Thanks,

Carlos.

[driftstyre]

I use water/water wetter, factory pump as well as a craig davies electric pump, 183 degree stat, stant cap, howe radiator core with custom end tanks and spal fans. Switching to straight water/water wetter will lower your temps a good amount. Dish soap and water is a good combo as well.

[chmercer]

dish soap?

mesage

[g6civcx]

Bill, I sent you a PM about the quarter glass. Please let me know what you think.

[inertiaticism]

dish soap?

mesage
From what I understand it lowers the surface tension of the water/coolant like WaterWetter does.

[ayuaddict]

crazy.

and one question, why fram?

from what i understand fram ANYTHING is complete shit, please correct me if i am wrong.

[driftstyre]

Fram racing products are great. The HP1 is the most widely used oil filter in racing. I cut mine open everytime I change it to check for contamination and the filter looks new. There's always little bits of fujibond in there:hsdance:

I know a ton of ALMS, Grand Am, World Challenge, WRC, European Rallycross etc. that use the exact same filter so its fine for me.

[SoSideways]

And where can you pick up an HP1 oil filter for the SR/KA/RB for us regular folks?

[driftstyre]

well, you need a filter relocation kit because it is only one thread pitch. The HP1 is Ford the HP4 is SBC. Pegasus, and other race hardware places stock Moroso/Mocal and Fluidyne relocation kits.

[SoSideways]

I see I see.

Thank you very much for the insight. Guess I'll have to stick with the K&N filter for awhile until I get the relocation kit.

[driftstyre]

I layed up two of the strakes for the diffuser last night. I used two layers of carbon but I might add another. I wish I had some insight as to how much side loading they will recieve. I guess I can't drive as sideways anymore. Or hopefully this will give me an excuse to keep it in line.
http://www.dentsport.com/gallery/d/5559-1/DSCF3003.JPG

[Quigs]

Here's the only glimpse of the car that I caught on film at VIR for GT Live. Sorry about the qaulity, my camera sucks.

http://s90.photobucket.com/albums/k270/quigs9808/?action=view&current=MPEG00542.flv

[driftstyre]

Damn, thanks a lot for posting that.

[Quigs]

No problem. That car is an amazing machine. Keep up the good work.

[Quigs]

thatguy: were you in the drift event at gt live at vir? if not you have a double! il post up vid if its you.

Is this the car you were referring to??
http://i90.photobucket.com/albums/k270/quigs9808/PHOT0077-1.jpg

[ayuaddict]

ahhh too bad you didnt follow this car with your camera rather than that civic.

[Quigs]

Haha yeah I know. I'm dissapointed I didnt have more film of the 240. I have to say, that Civic was suprisingly quick though...

[corey240]

Is this the car you were referring to??
http://i90.photobucket.com/albums/k270/quigs9808/PHOT0077-1.jpg
thats the one, iv been kicking my own ass for not getting as many pics as i had planed...i got some vid of it if anyone wants it, im loading up the tandems now on streetfire and yea man your filming in that spot where i wanted to go but damn it was cold, i brought shorts and short sleeve shirts considering that normaly that south its allways warm when i been there befor.

[Quigs]

^^^ Oh snap, yeah definately not a time for shorts/short sleeves. I was layered with long sleeve tees and hoodies and I was still freezing my ass off, so it must have been horrible for you. And I know I have more film somewhere, I just need to find it. Went spent a lot more time than I thought we would down by that part of the track. And I have some tandem vids too, so I'll post them up when I get some time.

[corey240]

your not that far away from me, im in keyser,wv. hopfuly next summer il be able to get in some events around the area since this year my car just didnt make it.

are you guys gona be racing at vir next year? (dentsport) i cant wait to see that thing done.

[sideview_180sx]

http://members.aol.com/bears4uall/car_0052.jpg

best pic I could find of an achievable fuel setup a lil over the top, but at least they don't have wiggin's clamps:naughty: .

what style are you going with on the diffuser??
http://www.mulsannescorner.com/Dome-JK4.jpg
or with tunnels and so forth
http://prototyp.org/construct/p35/images/20030714_P35-build1_0064.jpg
or the atypical j-land design
http://uras.co.jp/2006image/fd3s_gt/fd3s_gt_dfz.jpg

[driftstyre]

That green coupe is pretty badass. I love the wood rim wheel and the charred bumper.

I am making a diffuser more or less like the first one pictured. It isn't anywhere near that nice but it should work. This winter I will work on the bottom of the car and front splitter (which is halfway done).

I definitely would like to get a few events in at VIR (especially in the dry). I think once the car is developed a little more it could get close to a 2:05. A good gearbox, diff, aero and especially seat time should have close to 10 seconds in it on that long of a course. I'd like to break 1:15 at NHIS.

[Maximamike]

Hey Bill, I scored a video camera for that weekend at Limerock. What day are you going? I was planning on going down on the 18th because a friend of mine from F1 wants to check out the drift thing going on on the smaller infield track.

[driftstyre]

Mike,
I'll be there on friday and saturday.

Some progress pics. I need to make 3 more strakes/fins then some bonding and riveting. Its so goddamn cold in here it takes almost 2 days to cure with 60 minute hardener.

http://www.dentsport.com/gallery/d/5563-1/DSCF3011.JPG
http://www.dentsport.com/gallery/d/5565-1/DSCF3012.JPG
http://www.dentsport.com/gallery/d/5567-1/DSCF3014.JPG

[SoSideways]

OMG I need to change my shorts....

Bill, you're the man :bigok:

[ThatGuy]

Wow, Bill! Looks awesome, I can't wait to see it mounted! :rawk:

[Slidin240Wayz]

Are you going to the drift event? If you do, stop by the black zenki with Maroon hood and say hello.

Carlos

[driftstyre]

Some more progress pics. I will mount it up tomarrow night and take some pics then.

http://www.dentsport.com/gallery/d/5571-1/DSCF3030.JPG
http://www.dentsport.com/gallery/d/5573-1/DSCF3031.JPG
http://www.dentsport.com/gallery/d/5569-1/DSCF3029.JPG

[ThatGuy]

Is that the front splitter/undertray I spy in the background of the third pic? :rawk:

[motegineon]

what did u build the diffuser out of? then u just wrapped it in carbon material?

[SoSideways]

He said he was wrapping birch wood with carbon material for the front splitter, although it looks like he did that with the rear diffuser as well?

[driftstyre]

There are two layers of carbon on both the 5 strakes and the main flat piece. In between the two layers is this light, yet very stiff, dense cardboard type material I found at the depot. I was going to use this super light end grain wood but it seemed to warp a little bit once I cut it into pieces. I just lightened the cardboard material as much as possible and made cut out an X type shape for the main piece. I added a few little carbon pieces to the diffuser to stiffen certain areas up so it won't be mounted until tomarrow.
I worked on the exhaust tonight, gaining two more inches of clearance. I wanted to bring it up to the level at where the frame rail is so a flat bottom can be worked on this winter. There is also some serious scarring on the piping from VIR (cutting the up hill esses) and I guess some spectators said they saw white sparks coming from underneath the car! I made a bracket for the exhaust (see below) after finally finding a titanium 8x1.25 bolt from a broken zero2-R Ti Cusco lower shock mount. I also welded some sheet metal to the under side of the most vulnerable areas on the exhaust to give some extra cushion for when I cut (I love to cut corners Catalunya style!).
http://www.dentsport.com/gallery/d/5579-1/DSCF3043.JPG
http://www.dentsport.com/gallery/d/5581-1/DSCF3044.JPG
http://www.dentsport.com/gallery/d/5583-1/DSCF3045.JPG

[driftstyre]

http://www.dentsport.com/gallery/d/5585-1/DSCF3055.JPG

http://www.dentsport.com/gallery/d/5587-1/DSCF3047.JPG

http://www.dentsport.com/gallery/d/5589-1/DSCF3052.JPG

[Quigs]

^^^Wow that looks amazing already. Cant wait to see the finished project. Keep it up!! :rawk:

[Slidin240Wayz]

Very nice! Are you going to close the gap in in the rear section or leave it open?

Carlos

[driftstyre]

Carlos,
I will definitely close it this winter but I have a lot of little things to do before Lime Rock this weekend. It will be a much nicer rear end when the spring time arrives:coolugh:

[Bushido]

get some on track pics this weekend!

[Slidin240Wayz]

Are you going to run your car there?

Carlos

[ilia]

Where do you expect your center of pressure to be?

[driftstyre]

Carlos,
there is a COM time trial this friday and saturday on the main course. I'm going to leave the rain tires on for now and if it gets nice on saturday I will try to find a place to mount my dry tires. It looks like it might have light rain on friday:down:

ilia, do you mean at what speed? If so, I'm hoping about 30-40mph. I won't really have any way of telling without some means of testing. I wish I had more knowledge about aerodynamics as a lot can be gained but I'm a fabricator and spend most of my time thinking about that:confused:

[ilia]

The center of pressure is like an aerodynamic center of gravity. Because properly working aerodynamics will create a very real force on the chassis, that force can be measured (in lbs), and will have a center upon which it's acting. It's vitally important for that center of pressure to be in a good position on the car, especially relative to CG. As a very VERY general rule, it's usually ok to be just a touch behind the CG (implying a slightly rearward bias).

The real issue with aero, especially on sedan racing cars is the (relatively) soft spring rates of the cars. Any kind of dive or squat will either put the front wing or the underbody further into or out of ground effect, which will radically shift your center of pressure. That leads to all kinds of fun stuff like spinning into kitty litter at a buck ten when there's a wall 40 feet after that. You also have to consider interactions from any cars you may be trailing, as well as the effective slope of the downforce you're getting.

Let's say you're running a super efficient wing on the rear, and it adds 1lb of downforce for every 1mph. If your wing in the front adds just .5lbs of downforce for every 1mph, you'll be in a world of hurt very quickly, as you'll get progressively increasing understeer.

The other issue also has to do with sedan based road racing cars having very soft spring rates. An effective amount of downforce will compress a car's suspension by quite a bit. This results in your camber curves being optimized for one corner, but totally wrong for a higher speed one.

[Sky240PWR]

I really love what you've done with the car, I love seeing it in action. I think it's awsome you're doing what you wanted with it. I also wish I had more knowledge about aerodynamics, I'm working on a widebody 91 hatch, I'm no fabricator but I have alot of ideas. here's my car as it sits right now, and the second pic is a shitty photoshop I did, but you get the idea

http://i131.photobucket.com/albums/p302/sky240pwr/s1434b.jpg

the black under the car is supposed to be diffusers, the front bumper will be redesigned, the back bumper has a Ab-flug 300zx carbonfiber rear diffuser we fab to fit.
http://i131.photobucket.com/albums/p302/sky240pwr/IMG_2262.jpg

pic of bumper before diffuser
http://i131.photobucket.com/albums/p302/sky240pwr/IMG_2026.jpg

pic after diffuser, I wish it was alittle wider but it's too late for that, never mind that clay wing, I just wanted to get an idea of how it was going to look. the lights are R33.
http://i131.photobucket.com/albums/p302/sky240pwr/IMG_2257.jpg

I can't wait to see what you're doing with the rest of your project!...keep up the good work!

[ilia]

BTW, Bill, I would highly reccomend getting some nicer rivets for the diffuser. The improvement in detatched flow will be noticeable, and it's really not worth the effort to make a piece like yours and then have these big gnarly drag inducing rivets on it.

[ThatGuy]

Sky240, please keep that lump of of fiberglass and bondo out of a thread dedicated to a true track car. Your car cannot compete and should not be in this thread. If you want to show it off, put it in the picture thread. You car has nothing in common with Bill's work of art, other than the fact it used to be a fastback 240.

[Sky240PWR]

Sky240, please keep that lump of of fiberglass and bondo out of a thread dedicated to a true track car. Your car cannot compete and should not be in this thread. If you want to show it off, put it in the picture thread. You car has nothing in common with Bill's work of art, other than the fact it used to be a fastback 240.do you feel better? you going to get better sleep tonight?...whatever floats your boat captin! we had something in common, we are both building wide body 240 and wish we had more knowledge about aerodynamics, he just did his rear diffuser and so did I, my car may not be a track car like bills but I'm sure even he can connect the dots, and i wasn't saying our cars were alike, they're both built for very different reasons

Bill, if I offended you by posting in your thread and putting these pics up, then I'm sorry.

[McRussellPants]

I don't need to be know what squeezing 5lbs of pure salt, battery acid and tabasco into my eyes feels like by stumbling on to pics of your car.

Cliffnotes: Your shit sucks, delete the pics.

[driftstyre]

You didn't offend me at all. Though its not my style I can still appriciate the work that went into it.

[g6civcx]

Everybody, please keep in mind that aerodynamics cannot be fully appreciated without wind tunnel testing at least a scale model.

Your wing may be the perfect airfoil, but keep in mind that the most important area is how the wing is fitted to the body. This can create high pressure area directly where the wing mounts to the body, and renders your whole wing useless. Nobody really knows without testing, but the smoother your mounting points are the better off you're going to be. You may want to pay attention to how the wing interacts with the body and perhaps smooth out the interaction a little bit.

Same goes with your diffuser. The purpose of the diffuser is to smooth out turbulence by creating numerous slipstreams instead of a huge gush of air running into itself and creating vortices

Your center of pressure is like your center of mass, except it's affected by speed. Different airfoils have different lift/downforce and drag characteristics. As your car gains speed, the front and rear will gain/lose lift/downforce and drag at different rate. What you want to keep in mind is you're trying to control how much effect the air has on your car. You may want slight rear bias, like he said. You may want your pressure center to align with your center of mass. It depends on what you want.

The other thing you may want to keep in mind is that your wing and diffuser will also exert side forces on your car at mid to high speed corners. They act like parachute and drag the rear of the car. This is because the front profile of the car changes when you're turning. You're exposing more of the side profile when you turn.

Your diffuser may be great going 150mph down the main straight, but depending on how your rear end is set up, it may upset your balance at say 80-100 mph mid to high speed corners.


The thing that concerns me is the shape of your rear bumper. Before you had the diffuser on, it looks like air could come up underneath the car and give you some lift at the rear. You may also think about how your hollow bumper may act like a parachute as well.

[chmercer]

"Everybody, please keep in mind that aerodynamics cannot be fully appreciated without wind tunnel testing at least a scale model."

retarded statment

unless you are running like factory backed gt1 and up, your shit will never be wind tunnel tested ever. this includes like 95 percent of race cars. lap testing is plenty sufficient for aero tuning on a semi professional level.

[ilia]

That's absolutely NOT a retarded statement. Wind tunnel testing is KEY to proper aero development, for the reasons that guy and myself outlined. Thorough CFD analasys is a substitute, but a poor one.

Interaction between the wing and the rest of the car, pitch and roll sensitivity, and interaction between cars is difficult to predict and should be left to people who know how.

Like my last post insinuated, messing with aero is kinda best left to the proffessionals. Running random wings on random places is not safe, because god forbid, it might actually WORK, and then you've got all sorts of issues (that I outlined previously).

[Ian]

Aerodynamic Development and trying to improve lap times are 2 different things

[g6civcx]

Well said. I spent years learning about aerodynamics, and months with motorsports engineering team using the supercomputer and a distributed cluster of 200+ computers trying to smooth out some of the airfoil as part of my senior research. We were trying to simulate particle flow in the slipstream on their Legends car, but it seems like I could never get the data points granular enough to actually model anything worth while. All the extra computing power just ended up costing more overhead to manage.

It sounded more complicated than it was. It's just trying to calculate what happens when a ball bounces off the wing. Then having multiple and smaller balls bounce off the wing and hit each other. The smaller and more numerous the balls, the better the results.

They got better results with about 15 minutes of wind tunnel testing with a scale model. Go figure.

Plus a scale model is considerably cheaper to test than the $10,000 per hour full size wind tunnel.

Aerodynamic Development and trying to improve lap times are 2 different things

They are one and of the same, Ian. You're always trying to decrease drag and increase downforce. It's just that aero design is beyond the budget of most people.

I guess we just wanted Bill to be aware that speculation without scientific testing is useless, and may be dangerous if some components do indeed "work". He's free to take stock in anybody's post.

[byhi]

http://i131.photobucket.com/albums/p302/sky240pwr/s1434b.jpg


^^^ dudes, this kid goes on every fuckign forum fishing for complements on his jack-a-man lame-o guy-blow kit... which was the hotness in 98....

give it up man....
shits weak




Bill, your setup looks nice, more pics, thanks

[driftstyre]

I really appriciate all of this input. I know this isn't going to be nearly optimal for this chassis, my car in particular. At the least, I am hoping that it will be better than nothing, for a start.
I know CFD isn't as good as a wind tunnel but it is a lot cheaper than building an exact 1/8 scale model (though there is a wind tunnel down the street that could fit a 1/8 model in it)
What would be the most cost effective way to get my exact setup (once the bottom is flat and the front undertray are complete) into CFD?
I am also going to close up the rear end so it will minimise the parachute effect it is having now. Thanks again for taking the time to give feedback.

[ilia]

Bill,

Although modeling the car on good analisys software would be very challenging and time consuming, there are some basic things you can do to most definately improve things.

First, like I said before, as a rule, more wing=more spring. If you can figure out what kind of forces you're working with in lbs, you can run that much stiffer of a spring with maybe a bit of a higher ride height, so that when you car is at it's optimum operating speed, your ride height will be where it used to be before aero, which will leave your camber curves alone more or less, so if they've already been optimised with some kinematic analisys ahead of time, you won't lose all your hard work.

I would strongly suggest getting rid of those rivets and using a specialised streamlined fastner or rivet. They are not much more expensive and will really help the drag and detatched flow side of things. You don't really want non-laminar flow on a piece you expect to be making good, efficient downforce.

Simply put, a barn door sitting at an angle flying through the air will make downforce. It just won't be very efficient.

I'll post a few more things later, I've got to get back to work!

Also, please excuse my spelling, being foreign sucks sometimes. :)

[Sky240PWR]

You didn't offend me at all. Though its not my style I can still appriciate the work that went into it. thanks!....I'm not going to respond to the haters in your thread(about me), that would be rude.
sorry again.

[DriftSpecial180]

That is an S13. :duh: :loco:

Uhh oops, there was supposed to be "my" in there. ugh

"will you do MY S13 next?"