Aerodynamics On Skylines

[fr0st]

I haven't seen a proper aerodynamics discussion on SAU so I'm going to start one

I did search for any discussion on it but nothing turned up.

Has anyone done any major aerodynamics work on any cars and logged the results?

I managed to pick up a copy of "Race Car Aerodynamics: Designing for Speed" which I'm yet to read but the basic improvements I'm thinking about would involve a splitter, partial under tray and a diffuser. Evo's seem to have good results with roof placed vortex generators which is probably worth experimenting with aswell.

Lastly, and probably least important, does modifying the aerodynamics exclude you from certain racing classes?

My car is just for fun, I'm just curious about the rules relating to aero.

Thanks all

[siddr20]

I guess the only improvements i see are wings and diffusers for downforce.

But i see this as a wank/rice factor than anything else..You wont even notice anything.. I feel anyways!! for normal street driving that is..

I think nissan did a study on the 34, before it released its gtr: on what wing to use and im sure they did a vast study on difusers.

Diffusers are great to minimise turbelance(sp?), and i guess it would cool the diff as well.. So will be worthwhile upgrades if you ever need it!!

However, im sure professional track car drivers would have thought of aerodynamics, but lets face it.. Skylines arent like F1s and arent state of the art!!

Also comes down to money in the end.. Most of us couldnt afford to put it in a wind tunnel and test it out hahah..

Actually would be cool if someone has actually done a air-velocity test on a skyline..

However, with most huge bodykits ppl have, its gonna increase the drag.. LESS drag=GOOD!! lol

another point i should note is that, less resistance in front the wheels will aid to improve less drag.. I dont think we can do this in the skylines lol..

For example look at the f1s.. They got nothing in front of the wheels.. less drag!!

Anyways i wanna know as well if anyones done a study on this.. esp on skylines..

Edited May 25, 2007 by siddr20

[irokin]

another point i should note is that, less resistance in front the wheels will aid to improve less drag.. I dont think we can do this in the skylines lol..

For example look at the f1s.. They got nothing in front of the wheels.. less drag!!

Actually I think you'll find uncovered wheels create a substantial amount of drag. If you have a look at light aircraft with non-retractable gear you'll notice often they have wheel pants. This is to minimise drag and usually results in an increase in cruising airspeed and decrease fuel consumption.

http://www.experimentalairplane.com/canopy/wheel-pants.jpg

[Duncan]

well this could be interesting....we do have smoe freedoms with the sports sedan we are building (rear wing and front splitter). Production or Improved Production rules don't allow any aero, and none of them allow undercar diffusers/flat floors.

But to start with aero over the car, it would be interesting for someone to do some wool tuft testing on them one day

With the evo vortex generators I'm pretty sure they wont be any use on a skyline coupe. They are to pull the airflow back onto the rear window to stop turbulance - but the skylines have a much flatter rear window and probably dont have the same problem.

would be interested to see if any of those ricey front wing extensions make any difference

[sbmotorsport]

I haven't seen a proper aerodynamics discussion on SAU so I'm going to start one

I did search for any discussion on it but nothing turned up.

Has anyone done any major aerodynamics work on any cars and logged the results?

Firstly i am no aerodynamisist, but from some of the testin i've been apart of at work on the supercars (holdens/fords), areo has alot to do with high speed handling and max top speed. Cleanin up the aero on our cars have seen end of straight speeds increase in excess of 6kph!! The basically with aero ur tryin to minimise drag and gain downforce without gainin drag, also u need to try achive a aero balance (theres no point havin the 3 storey multi element rear wing without improvin the front aero.. the car would have unbelivable amouts of high speed understeer).. All the basic rules apply for most cars: keepin the air attached as much as possible, both above n below the car.. and havin the right chassis setup to transmit the aero force as best as possible to the tyres..

just my $0.02

[fr0st]

I've been doing a fair bit of reading on this since I started the thread and the idea of an undertray and diffuser is probably the most effective, but its a lot of effort.

Your reducing the drag under the car by smoothing out the flow whilst causing the air to flow faster (less turbulent flows faster). When air flows faster the pressure drops lower than the pressure on the top of the car and generates down force. This PDF probably does a better job than me at explaining - http://www.tfd.chalmers.se/%7Elelo/rvad/re...2_underbody.pdf

Another one I'm looking at trying is an air dam and splitter. The PDF touches on the air dam but not the splitter. The air dam just prevents more air going under the car to reduce the pressure even more. The splitter is a horizontal plate at the bottom of the air dam that extends forward a few inches. When the air hits the front of the car it creates a huge high pressure zone, combined with the low pressure of the air going under the splitter/air dam you can generate a fair bit of down force at the front. Pretty much when you have a high pressure on the top and low pressure on the bottom you generate down force, and the more surface area you stick in between them the more force you get.

RE: Vortex Generators. This is the Mitsubishi paper on them for the evo - http://www.mitsubishi-motors.com/corporate...2004/16E_03.pdf

Although Skylines don't have the same rear windshield angle, there is still a fair bit of separation between the car body and the majority of the flow above the car. The real gains come when you use vortex generators to direct more air towards a spoiler/wing.

Feel free to shoot down anything I've said... I'm still learning

[NISMO]

Maybe not as relevant, but a point to note.

I was looking under my V35 the other day and the first thing that stood out is how smooth and hidden everything is.

Compared to my 33, where you can lie underneath and look up straigh through to the bonnet, the V35 has like an undertray which runs through it.

It also has a little lip at the front of the undertray with like a clear plastic flap on it.

For a standard V35 Coupe it seems alot more throught has been put into aero compared to previous models.

Happy to take some pics once it comes back from complaince.

[al_zhiemer]

my GTR 33 has an under tray and i have removed both it and the foil of the rear wing, although around town i didn't notice any real significant difference, out on the highway was another story. the vehicles high speed stability had gon totally out the window, befor at 160 km/h the car felt comfortable on the road and didn't want to dart all over the road, it became more like a dodgey falcon wagon with stuffed shocks.

as of yet i haven't experimented with the placement of the rear foil angel, it is something that i do mean to get around to one day.

also of note is the benifits of smoothing out your under-carage is the gain in fuel economy, the slippery your car is through the wind, the less effort taken to propel it.

and with todays prices and my heavy right foot, i need all the help i can get lol

[noone]

Kinda relevant i guess I think nissan have done a fairly good job with the stock rear wing on the 32gtr as at highway speeds and above i(we used to have unlimited speeds in the NT) if you line it up with the demister lines in the rearview you can very noticably see it drop as you increase speed and rise back up as you slow back down, try it u might be surprised. and no I dont think its due too weight transfer as you accelerate or from standing on the brakes to stop even if you slowly evenly accelerate its quite noticeable surprised me a little

[topstage]

if you have lots of money and wanted to do serious aero, we are the guys, we built and developed race cars and lots of functioning cf parts including undertrays.

[r33_racer]

thats wasnt really helpful to the topic mate, thats more like a free plug for your business. Probably could have been justified if you contributed with some of your experience or knowledge on the matter and then hinted to topstage as a third party of which can supply such aerodynamic parts.

Not being rude mate, just letting you know because you could get a warning about busting the rules, unless your a site sponsored business.

If your interested in aero, there are quite a few books around on the technology used in F1 which is definetely the most advanced you can probably get for ground effects race cars.

[sav man]

In Targa we adjuested the rear wing on our R33 (from 3rd most downforce to 2nd most downforce), we couldn't belive the diference it made, the back stopped dancing under heavy breaking, and it stopped wanting to drift round sweepers.

Our car also has a flat carbon tray under the front (N1), and is ment to have a carbon diffuser on the back, but apparenty there often flogged on import, and Nismo want $4000+ for a new one, i'd be interested to see what extra difernce the rear diffuser did.

Edited June 7, 2007 by sav man

[342Four]

here is some interesting vortex generators called air tabs

http://www.airtab.com/

same principle as the EVO vortex generators, but they look smaller

this guy has done some experimenting with them on his mini cooper and is going to use them on his aerial atom

http://www.dpcars.net/ (click the mini cooper picture on the left hand side, page 6 right towards the bottom - dated 2/7/07 and also click the aerial atom picture - 6th pic on the left - page 4 last entry before 03/15/07 date)

so far from what ive read from this guy, its kept the dust off the back of his cooper!! the atom would be interesting when its up and running, as it is track only and high speed

ive also seen in the fabrication section a guy in the US made a fairing of sorts to go from the top entry of his front bar, to the top of his FMIC to reduce turbulence between the bar and the FMIC and increase airflow over his FMIC

anyway read away: http://www.skylinesaustralia.com/forums/in...howtopic=156651

it could reduce drag a fraction, plus 'cleans' up the air and keeps it straight all through the front of the car...

[LBR33]

I at the moment am having a new 400r bar made with a built in front under tray that goes from the bar to about the sump i will report on how it affects the car when i get it.

[scathing]

I was looking under my V35 the other day and the first thing that stood out is how smooth and hidden everything is.

Compared to my 33, where you can lie underneath and look up straigh through to the bonnet, the V35 has like an undertray which runs through it.

It also has a little lip at the front of the undertray with like a clear plastic flap on it.

Yeah, the 350Z is like that too. There's an undertray under the engine, and the rest of the undercarriage is designed to be as flat and smooth as possible.

The Track model (with a little under spoiler at the bottom of the front bar and a small diffusers in the rear tyre wells, plus that little "hump" boot spoiler) has a drag coefficient of 0.29, which is pretty low. I think the V35, without the flared guards, has a similar (if not better) drag coefficient.

It does it with zero lift as well. No downforce, but no lift either. Makes the car reasonably stable at high speed, but without the extra drag that most downforce-generating aero causes. In BMI's 350Z Shock video, near 180km/hr they found the car slightly less quick into a constant radius, banked, turn than an R34 GT-R but the nose was a lot more responsive than the GT-R's when in a slalom.

The new Porsche Boxster has an underbody tray that runs for about 2/3 of the length of the car from the nose.

[t01-100]

We've tried front and rear undertrays on a GTSt track car, the front on a couple of attemps certainly had good effect, but it needs to run atleast to the start of the gearbox to really work. The second time we ran a leading edge of about 3" overhang out the front under a GTR lip, it was constructed from marine ply. The first was all mounted inside the lip and was a zinc sheet shaped to suit.

For the rear we basically looked at the R34 V-Spec unit but made it longer and lower with the rear being higher than the forward section. It was also constructed of marine ply and it had four veins running straight. We didn't really gather any data on the rear tray as the car got cleaned up from behind by another car first day out... the longer front lip was removed in a gravel trap at the next meeting when the car went as close to rolling as physics allow... so we gave up!

We didn't see any overheating problems with what we trailed, but if too much was enclosed without consideration for extracting air I would expect this to become a problem.

I'll try and find some photos... looked trick and got plenty of attention from the punters, so who cares if it worked or not!

[benm]

Was getting my work van serviced today and noticed he had some custom made undertrays sitting up against the wall. Found out that my other mechanic next door makes them himself for both of their datsun rally cars to prevent rocks flying up and going through the floor pan, they are very light but strong enough to last 4yrs without any holes.

He makes them out of a woven fiberglass material here are some pics:

[mahum]

Want to restart this old post. A lot has changed since 2007.

Want to know what ppl have done with proven results.

[timmy_89]

I'm also curious as I am wanting to rig up a front splitter and possibly a rear diffuser for my R34 GTT.

[GeeDog]

Old topic, but thought I'd continue this rather than creating a new thread.

We have an R33 GTST, setup as a dedicated track car - BC ER coilovers, Whiteline swaybars, some adjustable suspension arms, 245 & 275 R88r's, 8 port front brakes, 320 or so RWKW from RB25/30 on E85, 2 way diff, etc.

We've recently started working on aero improvements, and have built a removable front end with a plywood splitter (has to be removable to get on & off the transporter). Rear is currently an aftermarket fibreglass GTR style wing - don't know who made it as it was on the car when we bought it. The blade is now stuffed - started with a split along the trailing side, which we glued & taped. After a stint at The Bend yesterday, the leading edge is now also split - son reckons he could see the centre of the blade (in the mirror) almost touching the bootlid near the end of the straight. Top speed reached was around 240kph, and lap times in the 2:16's (according to Harry's) on a very cold, drying track, so it is a fairly serious setup.

The new front splitter has also created an imbalance between front & rear, so its time to upgrade the rear wing.

We had a go at 3D printing wing sections, that we planned to assemble using aluminium tubes, but had too much trouble with warping. Have given that idea away for now.

We don't just want to replace the existing blade - we are after a wider wing, with decent endplates, that sits higher than the GTR wing. Ideally we'd like to keep within Time Attack Clubsprint rules, so not outside the body of the car in any plane.

We can buy a China Ebay wing, but the impression is that they are more for show than go. Shipped cost is around $900 - $1000, which is too much for something that may not actually work. Most of them aren't wide enough anyway.

I know we can buy a Topstage wing, but cost is $2650, plus freight, and I don't think that includes uprights. I have no doubt these are a good product, but a bit beyond the budget at the moment.

I've seen the Bee-R style wings on Ebay, but I have no idea if they are functional or not, and what the quality is like.

Does anyone know of any in-between options available in Oz? Has anyone used an Ebay wing, and have any thoughts to share? Any other sellers in Australia other than Topstage? Any input is appreciated. We are in SA, so a local supplier would be good.