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#1 Robstar

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Posted 25 January 2008 - 12:03 AM

Recently I had a bit of an idea and thought I'd just run it by you guys, see if there is someone who already thought of it or just found it wouldn't do much in a realistic driving world.

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Vortex generators are found on the back of Mitsubishi Evo's. They improve the flow down the rear window, getting more air to the wing/lip. Would this borderline 'Ricey' mod help the poor aerodynamics of a 240/260's rear? Do they even work in the first place? I'm still reading up more and more about this as I posted this thread, so if I find something that proves that shark fins on a car do jack all, then I'll just leave it at that.

  1. Vortex generators on cars can achieve measurable, scientifically proven improvements in car aerodynamics – reducing both lift and drag. The Lancer Evo is probably the shape of things to come – expect vortex generators (of whatever design) to be used on new cars, especially to improve the flow around corners towards the rear of the body.

  2. Commercially available (and cheap) vortex generators like AirTabs can achieve a provable change in car aerodynamic behavior. Even a single vortex generator will alter local flow behavior, something to keep in mind when considering airflow into bonnet scoops and at specific problem areas.

  3. Positive gains can be achieved only by practical experimentation. That’s the downside – the upside is that the vortex generators are easy to temporarily stick into place with masking tape, and just as easily removed if they are not achieving the desired results. They’re also cheap enough that buying ten or so for experimentation is a good investment.

  4. The use of vortex generators under cars has zero visual impact and looks to have excellent potential for reducing lift without increasing drag.

[Stolen information from Autospeed.com]

Give your opinions and even better, facts if anyone is a aerodynamics engineer.

#2 zr240

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Posted 25 January 2008 - 08:01 AM

I have wondered about those vortex gens on the roof of a 240. As most people say there is seperation on the rear hatch which causes areo issues.

Interested to see what peolpe rekon

Ash

#3 Robstar

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Posted 25 January 2008 - 08:58 AM

From what I've read in the past.. well nine hours, I've come to the conclusion that theoretically, they will help! Also if placing VG's on the top of your roof isn't your cup of tea, you can place six or eight VG's along the bottom of the tail end and it'll help with aerodynamic stability instead of just improving air flow if they were above your rear window. (Keeping in mind this is all at around 60km/h and upwards..)

But I'm mostly curious in to some real life testing on how this would effect the infamous fume smell in some z cars, obviously the lip spoiler helps, but I think with the VG's, it could further rectify that specific problem.

Also a good way to find out how the air flows on the back of the rear window for our 240/60z's would be to make a dot like grid along the back window, of short strings of wool and some masking tape to tape them to the window, the flow down the back end while driving in a straight line would show just how the air moves along the car.

Either that or a wind tunnel and last time I checked, they aren't exactly sold at Target! Hahahaha.

#4 V8Datto

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Posted 25 January 2008 - 10:20 AM

HybridZ have a huge forum section for Z's and windtunnel's.

Make's for an interesting read,

I've always wanted to know if the rear wing people put on there Z's makes a difference or if it's just there for show?

#5 620Z

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Posted 25 January 2008 - 10:41 AM

Some rear wings make a huge difference especially when you are on the edge racing around the track. Obviously size and design count for much of it's effectiveness.

#6 Robstar

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Posted 25 January 2008 - 10:42 AM

Well I think that's the best place to read on about it from now on, I should have looked there first! They've done some real testing as well.

http://forums.hybrid...ad.php?t=126574

#7 PZG302

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Posted 25 January 2008 - 12:43 PM

On my racing Z I have a MKII front spoiler and the Nissan Bob tail, as the rules stated at the time the rear spoiler had to be a genuine item. Previous I ran a RX7 series I birdbath.

Aside from making the 240 look really tough, well im opinion any way, the bird bath made a huge difference to the aero of the car. After a track session the amount of dirt, rubber, oil and other assorted grime on the rear of the car was incredible. The big wing produced a huge low pressure area behind it and literally sucked the back of the car down.

Turn 1 at Eastern creek could be driven on full throttle with out lifting. When we put the bob tail on, we found now where the same amount of down force, or drag. First time through turn 1 I tried it flat and nearly speared off down the drag strip as the rear end tried to overtake the front.

The front spoiler makes a huge difference no matter what rear spoiler is fitted. My first Z, an ex rally 260 didn't have one and at about 140km'h you could feel the front lifting badly, with the MKII spoiler no problems at all with the front wanting to fly.

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#8 Hunter

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Posted 13 May 2008 - 12:32 AM

http://cgi.ebay.com....1QQcmdZViewItem

Check out the above link. It has diagrams of the angles and a pic of them installed on a 300ZX

http://www.vortekz.com/ Cheap too roughly $45.00 inc postage

#9 Dingo Dave

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Posted 01 July 2008 - 08:56 PM

I must say i have considered it. I may try to contact my friends who is an airospace engineer in the racing scene and see what he says.

#10 Hunter

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Posted 02 July 2008 - 06:12 AM

angelus

Post his info here we would be interested in what he has to say

#11 Scando

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Posted 02 July 2008 - 01:44 PM

I've always wanted to know if the rear wing people put on there Z's makes a difference or if it's just there for show?


I'm running the little Nissan bobtail wing too.  When I put it on the car it went about half a second quicker but I also put noltec bushes through the car at the same time so I think that was what made it quicker.  The only place I can feel the effect of the wing is through the sweeper on the back straight at Symmons Plains.  Speed is normally 210-220 km/h through there and I can feel the back really stuck to the track and it just gives a slight push in the front.  There aren't any other corners on our two tracks in Tassie that are really fast enough to feel the effect.

#12 Dingo Dave

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Posted 13 August 2008 - 10:48 PM

Ok here we go people. I asked the question. Does VG work. I have seen them on evos and wondered.
response: yeah, vortex generators work but you've got to be careful - they can easily make thing worse rather than better.
me:So I figure they disrupt the air flow to make it run with the body of the car.
response: More or less correct on VG function, on something like the evo they help the air stay attached as it goes down the back screen. Similar principle to the dimples on a golf ball actually.
me: I saw an evo the other day with a lot of cosmetic stuff all over it and just thought most of that would be slowing it down and making it harder to cut through the air.
response: Your certainly right about many of the cosmetic kits you see though - I have actually seen a few with the wing section the wrong way up so that it'd actually be producing lift...

So there you go. I didnt realize they did the same thing as a golf ball. So the motto of the story is to check first and then add. I also asked what they use more a computer or a wind tunnel. he said it takes a lot of computer power to generate the same thing as a wind tunnel they are good but the wind tunnel is always the last way of testing. to build a model and then subject it to the wind tunnel with special scales that measure the roll and force is the best way.
hope this is usfull.

#13 ol_skl_jp

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Posted 14 August 2008 - 12:13 PM

Thats exactly right Angelus, the VG's create turbulence which allows the air to stick to the body of the car. If using a wing creates greater downforce, and makes it more streamline. A program we use to simulate this is flowlab.

I really dont think these are necessary for the old z's becuase of the roof goes to the bbot gradually (not like a sedan where there is a steep plunge) this allows the air to stick to the body of the car.

#14 nat0_240_chevZ

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Posted 14 August 2008 - 01:00 PM

untill it hits the end of the hatch, then large amounts of turbulence, also causes you nast exhaust smell!!! ie suck the ex gas straight back towards the back of the car.
the trailing edge/shape of a body through a liquid is the most important, not the leading edge.

if you look at solar cars for example, note the large slightly changing radius on their leading edge, and the very sharp trailing edges @ the rear, promoting laminer flow after the air/liquid has been re-directed around the shape of the moving object, the solar car our tafe ran in the race to darwin had a fair few hours in a wind tunnel to prove its aero design in which it did very! well.

nat0

#15 Dingo Dave

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Posted 05 September 2008 - 07:09 AM

Yeah we spent ages in a wind tunnel doeing the spirit of canberra. spent more time in a wind tunnel doing a hydrofoil. then in a liquid bath to make sure the foils were going to do what we needed them to do. It looked mad on the water too.




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