vortex generators

[HyperTek]

lets talk about em.


anyone throw some on? just curious if there was any differences made. Dont give a fawk about how they look, this is all for aero tuning not puttin silly shit on ur car.
Seem to be a better benefit over roof spoilers with no background besides the typical "it looks tight"

Mitsubishi documentation on the effects
http://www.mitsubishi-motors.com/cor...004/16E_03.pdf

http://www.manufacturersdepot.com/SPD/vortekz-universal-vortex-generators-black-10-pack-vortekz-vortex-generators-are-universal-to-fit-virtually-all-cars--trucks--vans--suv's--rv's-etc-----800000A6-1180622063.jsp

[awesomenick]

I saw a tractor trailer with a ton of these airtab things on it the other day.

http://www.airtab.com/

They must do something cool if they spent the money to buy them. But I haven't personally tried it.

[BBSilvia]

haha i actually was thinking of putting it on my car...but decided not to, but my buddy put one on his subie looks nice but horrible fitment so dont buy knock off or super cheap!

[blownmotor]

They do work but it has to be placed at an optimal area with the correct size and design. And we need a wind tunnel to see where our seperation point is on all of our different model S platforms

[Def]

Originally Posted by blownmotor

They do work but it has to be placed at an optimal area with the correct size and design. And we need a wind tunnel to see where our seperation point is on all of our different model S platforms

It's easy to tell where the separation point is on your car - just drive in misting rain and check where it stops streaming on the roof.


I rock some delta-shaped vortex generators like the Mitsubishi article investigated. If you actually read the research on VG's, you'll see they are pretty insensitive to placement as long as you're in the general ballpark. I get less dust on the hatch for sure, so they must be doing something.

[derek_s13]

dstar put these on his car. first 240 i've seen with em. matches the style he went for this time around i guess.

EDIT: yeah here:




get him in this thread, ask him and shit.

[HyperTek]

http://pmsc.on.ca/bulletin/2005/JulAug%202005.pdf

they expect it must be improving the effectiveness of the rear spoiler

[ryguy]

I just helped my buddy put one on his Lancer. I didnt notice any difference, but who the hell knows, that Mitsubishi report was pretty scientifically conclusive. Plus, girls think random bits of plastic on your car are sexy.

[JRas]

Originally Posted by ryguy

I just helped my buddy put one on his Lancer. I didnt notice any difference, but who the hell knows, that Mitsubishi report was pretty scientifically conclusive. Plus, girls think random bits of plastic on your car are sexy.

because he wanted to look like an EVO

[sldbyuramg]

Originally Posted by JRas

because he wanted to look like an EVO

+1 lancers are gay as shit especially when people try to make them look like evos.

vortex generators are great if they are used in conjunction with the correct wing height for the targeted speed.

what im trying to say is that an evo mr vortex generators are optimal between "AROUND" 50mph to 80mph. between those speeds it supposedly adds 10 to 15 lbs more of downforce than without one. if you just buy one off EBAY for a 240sx it will help but it may only help at 100mph to 150mph... if you have no wing or if your wing is too high it may only work at very low speeds.
basically if you cant get your car into wind tunnel to find the optimal settings it may be for LOOKS only. and there may be a huge difference between hatch and coupe setups.

it will help with downforce, just at what speed may be a wild guess for our cars until someone does some real testing

[initial_drifter]

http://zilvia.net/f/showthread.php?t=175795

it's about roof wings but it changes to VG's

good read

[S14SwimShark105]

roof wings don't do anything but mess up the airflow, it creates a suction action causing air to rush up the back window.

Don't know if this has been posted yet but everyone should read this, it's a really good review on the vortex generators. http://www.autospeed.com/A_3058/cms/article.html

[g6civcx]

Aero "tuning" is not about piecing together individual parts. Airflow interacts with the whole car so the car as a whole must be tested, ideally in a wind tunnel, to understand the full effect of a particular aero mod.

For example, learn from my teacher's mistake. He designed a very effective wing shape with full wind tunnel testing data. Then he installed it on the car and it didn't work so well. Downforce was nonexistent and drag went up significantly. His mistake was designing the wing without the car. The wing-to-body interaction is more important than the actual wing itself. What he found was that there was turbulence at the base of the wing, which stalled the air from ever making the wing effective.

Moral of the story: design all aero parts with the actual car to be applied on.

While the VG may be good for an Evo with a boxy frontal and side profile, S and Z cars, and especially fastbacks, have a more teardrop shape. It's not clear from Mitsu's white paper what the effect would be on our cars. Mitsu specifically limits their discussion to a sedan with a trunk. See at least page 11 column 1 paragraph 3, and throughout.

I say the best way to test the theory is to build a model and make your own wind tunnel with a big fan and a smoke machine Or if you're a computer genius you can run a simulation.

If you want your wing to truly be effective, the rear wing needs to be higher than the roofline! This is because airflow will not drop down at the rear windshield enough to make the wing work, regardless if you have VG or not. This is worsen as speed increases. To counter this, you need a large rear wing sticking up above the roofline to be in the line of airflow.

Otherwise I wouldn't waste money on aero stuff unless you really want the parts for asthetic value.

[HyperTek]

thats why we discussin it... theres side effects to everything.. I say could be looked at.

I threw a roof spoiler on my old S13... along with a kouki wing . pretty sure that made both the items useless lol

theres alot of stuff that would affect the overal aerodynamics, pop up headlights in up position, wheels sticking out, exhaust pipes sticking out over the rear bumper etc..

Im curious if there was any homework done in the design of vented fenders.

[suaknee]

I've always wondered about these too.

[GSXRJJordan]

^^^ Vented fenders, probably not. Besides, they're for engine/brake ventilation, not downforce (air rushing past the fenders pulls hot air from that area out).

What g6 said about the "car as a whole" is absolutely true though, you can't test individual parts effectively.

[HyperTek]

high speed tunin nukka!
im still buildin my deck spoiler

[sldbyuramg]

im all about high speed tuning... i did a high speed trip from Alpine in san diego to Phoenix in 4 hrs well 4 hrs and 2 min. with a 10 min stop in yuma for gas. i was on my top speed limiter for 2 hours total and the longest run was 45 min consecutive. i had my Valentine 1 for safe travel... EVO8 with MBC set to 20lbs boost K&N drop in filter, turbo back exhaust, and tanabe lowering springs

[S13_marine]

If you have no wing, VG's aren't going to do anything. The purpose of a vortex generator is to disrupt airflow, or create turbulance, but in a specific air stream in order to use that air to create a desired effect on another surface. Aircraft use them mainly to disrupt air movment over the wings, creating more air surface to hit the ailerons etc... So, in short, unless you have a rear spoiler or wing, it not gonna do anything but look EVO-ish. But with the right sized vortex generators and an ajustable wing, you'd have a pretty effective way to create more downforce in the rear.

[Def]

Originally Posted by S13_marine

If you have no wing, VG's aren't going to do anything. The purpose of a vortex generator is to disrupt airflow, or create turbulance, but in a specific air stream in order to use that air to create a desired effect on another surface. Aircraft use them mainly to disrupt air movment over the wings, creating more air surface to hit the ailerons etc... So, in short, unless you have a rear spoiler or wing, it not gonna do anything but look EVO-ish. But with the right sized vortex generators and an ajustable wing, you'd have a pretty effective way to create more downforce in the rear.

Vortex generators create a streamwise vortex that energizes the flow to reattach it to a surface. In the case of an aircraft, it's trying to get the flow reattached on the wing at higher angles of attack such that the control surfaces are actually acting in airflow. They typically use dual delta wing shapes with a set ~15 deg angle of attack to the incoming streamline.


As far as your wing needing to be above the roofline - totally false. The flow is not separated from the roofline back when looking at a velocity plot. Yes, a wing 2" off the decklid will not work well, that's common sense and a simple tuft test could tell you that. Once you get about 12" off the deck you're probably going to be in "mostly" clean flow, and above 14" on our cars it's probably going to be almost completely linear and horizontal flow.


You do not need a wind tunnel to do aero work. In fact, some simple tools like a manometer/inches of water pressure gauge, some wool tufts plus tape and a little knowledge will go a LONG way towards helping out aero on your car. I'm betting most people who say you absolutely must have a wind tunnel to do any aero work on a car have never even stepped foot inside a wind tunnel, or have an idea of what really goes on inside one. I use 'em all the time, and I'm saying large general changes are easy to make without analyzing things within a gnat's ass. It's called back of the envelope engineering, and it's more common than you think, and the GOOD engineers can make absolutely amazing observations with some observations and a few simple calculations about what needs to happen(in some cases).

[g6civcx]

Let's look at what I said:

Originally Posted by g6civcx

If you want your wing to truly be effective, the rear wing needs to be higher than the roofline! This is because airflow will not drop down at the rear windshield enough to make the wing work, regardless if you have VG or not. This is worsen as speed increases. To counter this, you need a large rear wing sticking up above the roofline to be in the line of airflow.

Merriam-Webster defines "truly" as "in a proper or suitable manner".

You said:

Originally Posted by Def

As far as your wing needing to be above the roofline - totally false. The flow is not separated from the roofline back when looking at a velocity plot. Yes, a wing 2" off the decklid will not work well, that's common sense and a simple tuft test could tell you that. Once you get about 12" off the deck you're probably going to be in "mostly" clean flow, and above 14" on our cars it's probably going to be almost completely linear and horizontal flow.

Question: is the roofline higher than 14"? If no, then my statement is false. If yes, then my statement is true.

You do not need a wing that high, but a) would a wing that high work, and b) would a wing that high work better than a 14" high wing?

You don't need $200 to buy a $100 item, but would going to the store with $200 to buy the $100 item be "in a proper or suitable manner"?

Based on your asserted experience, you should know that in order for an airfoil to achieve the desired effect at lower air speeds, the wing needs to have a larger angle of attack and larger size = picnic table wing. You can probably explain that better than I can.

I said:

Originally Posted by g6civcx

I say the best way to test the theory is to build a model and make your own wind tunnel with a big fan and a smoke machine Or if you're a computer genius you can run a simulation.

You said:

Originally Posted by Def

You do not need a wind tunnel to do aero work.

Merriam-Webster defines "best" as "excelling all others".

Question: is the wind tunnel, even a mini one, the "best" way to measure aero data? If no, then my statement is wrong. If yes, then my statement is right.

Originally Posted by Def

In fact, some simple tools like a manometer/inches of water pressure gauge, some wool tufts plus tape and a little knowledge will go a LONG way towards helping out aero on your car.

I do not disagree at all about what you said. I specifically said that you can also do a computer simulation. This means that I said that there are other ways to do aero testing other than using a wind tunnel. My experience is in computer simulation so I bring that in. Anyone else with more mechanical experience can bring their experience to the table.

Originally Posted by Def

I'm betting most people who say you absolutely must have a wind tunnel to do any aero work on a car have never even stepped foot inside a wind tunnel, or have an idea of what really goes on inside one. I use 'em all the time, and I'm saying large general changes are easy to make without analyzing things within a gnat's ass. It's called back of the envelope engineering, and it's more common than you think, and the GOOD engineers can make absolutely amazing observations with some observations and a few simple calculations about what needs to happen(in some cases).

As far as I know, nobody in this thread suggested that you "absolutely must have" a wind tunnel to do aero work.


I don't mind getting slammed when I deserve it, but please at least have the decency to address what I'm actually saying, not what you think I said. For someone with your asserted knowledge, you should be helping instead of slamming other "engineers".

Are there any professionally certified engineers around here? Yes, there are a few.

Engineers are supposed to be free thinkers and not be constrained by conventional wisdom. Most discoveries are made by accident when people play around and experiment with stuff. Yes, you have to understand the basic fundamentals, but as far as engineering design goes, your mind should be free to play with the full range of natural phenomena around you. Even our Founding Fathers acknowledged this when they set up our legal system. Our patent laws reads "Patentability shall not be negatived by the manner in which the invention was made". My favourite inventor is Thomas Jefferson, and he promoted this concept.



Back to topic, please.

It's futile to discuss this further without trying to figure out what you want to do.

What speeds will you be using the vehicle for? Short or long roadcourse? Do you want to reduce drag or do you want high downforce? Some combo of both?

[Def]

Originally Posted by g6civcx

Question: is the roofline higher than 14"? If no, then my statement is false. If yes, then my statement is true.

You do not need a wing that high, but a) would a wing that high work, and b) would a wing that high work better than a 14" high wing?

The boundary layer on your trunk area is not anywhere near 14" thick. You can have an airfoil be below your roofline, but still in completely horizontal flow. It heavily depends on geometry of course, but the air doesn't just flow straight off your roof. VGs just try to influence this flow a bit to reduce overall drag, and you can also get the side benefit of getting a greater lift from your wing by increasing pressure if it's not in completely developed flow.

Based on your asserted experience, you should know that in order for an airfoil to achieve the desired effect at lower air speeds, the wing needs to have a larger angle of attack and larger size = picnic table wing. You can probably explain that better than I can.

Yes, you need a big airfoil to do much below about 60-70 mph. Angle of attack can produce more downforce up until the airfoil stalls(flow separates), which can be influenced by airspeed to varying degres.

Merriam-Webster defines "best" as "excelling all others".

Question: is the wind tunnel, even a mini one, the "best" way to measure aero data? If no, then my statement is wrong. If yes, then my statement is right.

I would say no, because what is the purpose of a homebuilt wind tunnel other than to just "see" flow. Even if you did particle imaging velocimetry to some degree and could see the separation points and flow vectors you're not getting the majority of the story by knowing how efficiency your airfoil is from a lift/drag standpoint. Full scale testing is better and cheaper in this case since you can just take your car out on the road and see what is ACTUALLY happening on your ACTUAL car.

I do not disagree at all about what you said. I specifically said that you can also do a computer simulation. This means that I said that there are other ways to do aero testing other than using a wind tunnel. My experience is in computer simulation so I bring that in. Anyone else with more mechanical experience can bring their experience to the table.



As far as I know, nobody in this thread suggested that you "absolutely must have" a wind tunnel to do aero work.

No one has mentioned you definitely need a wind tunnel, although your post did go a little on the side of excess analysis for doing some minor work to a 20 year old chassis, but that's fine, it was likely useful for some people who didn't even think about actually testing anything.

I don't mind getting slammed when I deserve it, but please at least have the decency to address what I'm actually saying, not what you think I said. For someone with your asserted knowledge, you should be helping instead of slamming other "engineers".

I never slammed you, I just made a general comment about the common idea that some seem to have of needing to do exhaustive amounts of testing to improve aero efficiency when you can get most of the way there with just a few hours of easy work and a little knowledge which is readily available. It's like saying you can't tune a car without a full OEM engine stand and instrumentation lab that would cost well over a million dollars. It's not feasible, and a dyno plus a little consumer grade data collection does a reasonably good job. I guess I just think the approach to aero should be the same way for our cars.

It was never my intention to make my post seem hostile, so sorry you took it that way, but I do think my suggestions are a bit more grounded than lots of the testing suggestions that have been thrown out thus far.


As for CFD - from personal experience I really don't like consumer grade CFD stuff, especially for something as complex as an intricate 3D surface interacting with a 3D airfoil. Even the $$$ CFD packages run on our big computing cluster is not that accurate when you get into more complex stuff. It'll typically work out kinda close when you plug actual test data in there, but rarely does the model converge on something resembling reality for more than a very narrow window if the CFD guys are lucky.

[CKAMC]

I myself am looking into getting a set of sards vg's for my s14.. much more functional than a roof spoiler. Might get a APR spoiler later on to help with its function

I am still trying to find out how to best place these without having to rent out a wind tunnel.

here is quite a few placed on a RD.... rather extreme FD


but buy the looks of the wing height in the sards image... doesn't look like it needs to sit up there that high *the actual wing*



sards are a bit bigger than the oem evo or the chargespeed one's being sold right now.

[Def]

Those SARD VGs aren't going to make much of a vortex being almost parallel with the flow for most of the middle of the roof. They need to have some angle of attack to the incoming air to make a good vortex. That said, those things are ginormous to the point of HURTING things more than helping. You're going to add way more drag with something sticking up 4-6x the boundary layer thickness than a proper VG that's about 1.5-2x the BL thickness. So you might reattach flow on the rear window well, but sticking that much crap out into the flow doesn't come without penalties(drag). Plus there is a clear point of diminishing returns once you get about 2x the BL thickness as far as generating a more "useful" vortex.

[HyperTek]

im curious if the japanese companies do actual wind tunnel testing? i recall back when sleepy eye controllers where designed to be air ducts lol

[Kougeki]

Unless you're actually going like 70+ MPH, i don't think these make a difference, the Chrysler Crossfire's wing goes up once it hits 60 MPH.
If you're on the freeway constantly, it probably can't hurt.
If you're sliding... why put one on? ?

[CKAMC]

Originally Posted by Kougeki

Unless you're actually going like 70+ MPH, i don't think these make a difference, the Chrysler Crossfire's wing goes up once it hits 60 MPH.
If you're on the freeway constantly, it probably can't hurt.
If you're sliding... why put one on? ?

not everyone here is into drifting.....

yeah I know there are a few of us... try and keep us in mind

[Kougeki]

Originally Posted by CKAMC

not everyone here is into drifting.....

yeah I know there are a few of us... try and keep us in mind

No, i know not everybody's into drifting.
But that's why i said that IF you're on the freeway or doing high speeds all the time, it can't hurt.

[HyperTek]

might be good for.. well.. incase you stall in mid air... i kid i kid

[NI_YON_Zenki]

Nice Rhyme Tek.


OOH, 757 Baby! Jumbo Flow. High Up in the sky Crushin' folks Belly Below!

lol. but, yeah, Nice rhyme Tek.