vortex generators

[Idahotom]

I've been using them for years, on airplanes. And in fact had some left over from my last installation, and too much time on my hands I guess, so I went ahead and vg'd the aft portion of the roof line on my '08 HB.

The spacing and angles are the same used in aero apps, it has been determined that putting them closer doesn't do any better, but adds more drag. Same with the paired angles, that's all been tested before. So it made it real easy to just use the supplied template and double side carpet tape to install. If I decide to make it permenant I'll glue them on with the same stuff supplied in the airplane kit. BTW, we're talking below 100 mph airplanes here.

The 1.5 mile dirt road to get to my place will make a perfect test site to spot any changes in the airflow on the rear window. What I am hoping for is a more attached airflow over the rear, and that is what vg's do. On a wing they keep the airflow attached to the upper surface longer, as the angle of attack increases when landing or flying slow. This allows for slower landings and as important better control authority at the lower speeds as you have more and "better" (non disturbed) going over the control surfaces. How this will translate to the Yaris is anyones guess, I did it halfway for a laugh (and no doubt will tell people who ask that it adds 10 mpg:rolleyes:) and just maybe it may be not a bad idea.

I thought of extending them down along the sides, and may, I'll wait until I drive the wind tunnel a few times. I'll report back on results, if any.http://i.imgur.com/WPcQyiM.jpg (http://imgur.com/WPcQyiM) The airplane, a Rans S-7S kitplane. 3.5 GPH car gas at 90 mph. BTW, I've noticed that the guys who fly the big Cessna's or Maules (8 to 14 GPH) also drive big pickups or SUV's, they wouldn't be caught dead in a Yaris! Some of us just like to do more with less I guess:iono:http://i.imgur.com/F2Vf2km.jpg (http://imgur.com/F2Vf2km)

[Mittelklasse]

What a coincidence :laugh:. I've installed them since one week ago.

However, My design was drawn from the Mitsubishi's type and is significantly larger than yours.

http://image.motortrend.com/f/8523433/112_0512_wrx_evo_18z+2006_mitsubishi_lancer_evo_ix _mr+vortex_generators_action_view.jpg
http://i519.photobucket.com/albums/u354/Krotchyminator/Untitled-2.jpg

Need a bit more of testings. But my butt-o-meter says the car is now more stable at high speed (>80 MPH) :biggrin:.

[Mittelklasse]

Also, I'm planning to apply a pair to the side mirror trims. I saw the new Camry Hybrids and Prius Cs have them :thumbsup:.
The new Mercedes S-Class (W222) also has VG-ribs built onto the side of the side mirror housings.

http://paultan.org/image/ecodrive10.jpg
http://static.ed.edmunds-media.com/unversioned/img/long-term/2012-toyota-camry/2012_Prius_C_1600_thingy_mirror-thumb-717x478-127766.jpg

[Idahotom]

Very cool..... yeah mine are smaller, and just like the ones we use on the wings of the planes, in fact extra left over ones. So zero cost anyways.

I just noticed the streamers on the area downwind of your vg's, that looks like exactly the kind of airflow you'd want, nice and laminar. I haven't tufted my HB, I may do so if I get more serious about this, as that is the way to see what's really going on.

80 mph is high speed in my book!

[Idahotom]

Since reading the post about "being more stable at high speeds", it occured to me that I had not had my HB up to highway speeds since the vg install, just secondary road/ 45 mph driving. So, I made a special effort to take the interstate into town, and I got up to the blistering speed of 65 mph and then almost 70, rather then my usual 60. The results were very interesting.

I should mention I took EVERYTHING out behind the drivers seat, 2 years ago, including that framework that supports the seat and maybe adds stiffness to the unibody. I have good tires and a aftermarket rear sway bar, and the front end is set to specs. So, the highway speed straightline handling to date, which, to be generous, could best be called "sporty", has just been something I have learned to live with. I just figured being so light, it was to be expected. That and maybe that steel tube structure for the seat was allowing some flex, or something. Or, maybe the heavy semi traffic and the resulting dished out slow lane (where I am all the time) had the Yaris needing pretty constant attention to not look like I was driving impaired. No big deal really, l like everything else so much this was a small price to pay and just part of the deal, I'm no whiner.

BUT, now with the vg's......it's like it's on rails! The thing tracks like a much heavier car now, and the work load is much reduced, the difference is amazing! Too soon yet to tell if there are any mpg changes, but just the handling difference makes this experiment a success. Furthermore, it was pointed out to me that I had them too far rearward, they need "room to work". That is, moving them forward a bit would allow the airflow a little more room to get re adjusted somewhat. This made perfect sense to me, as on the airplane we put them ahead of the area we want the airflow to stay attached to, by 6 or 8" or so. So, I pulled them all off (just double sided carpet tape) and then just to make sure I wasn't imagining things, drove it on the interstate again, and, the squirrley handling was back! So, no question the vg's are doing something, and that something is good. They are now semi permenantly glued down right behind the antenna, about 6 or 8" from the rear deck drop off, and while I have yet to drive it at freeway speeds since the move, I am real pleased so far. I will report back after a couple tanks mpg wise, if it's the same I'll be happy, I'm thinking whatever is going on to effect the handling so much (less ass end drag and turbulence?) must have favorable results on the mileage, that would be a real bonus if it did.

[CTScott]

Since reading the post about "being more stable at high speeds", it occured to me that I had not had my HB up to highway speeds since the vg install, just secondary road/ 45 mph driving. So, I made a special effort to take the interstate into town, and I got up to the blistering speed of 65 mph and then almost 70, rather then my usual 60. The results were very interesting.

I should mention I took EVERYTHING out behind the drivers seat, 2 years ago, including that framework that supports the seat and maybe adds stiffness to the unibody. I have good tires and a aftermarket rear sway bar, and the front end is set to specs. So, the highway speed straightline handling to date, which, to be generous, could best be called "sporty", has just been something I have learned to live with. I just figured being so light, it was to be expected. That and maybe that steel tube structure for the seat was allowing some flex, or something. Or, maybe the heavy semi traffic and the resulting dished out slow lane (where I am all the time) had the Yaris needing pretty constant attention to not look like I was driving impaired. No big deal really, l like everything else so much this was a small price to pay and just part of the deal, I'm no whiner.

BUT, now with the vg's......it's like it's on rails! The thing tracks like a much heavier car now, and the work load is much reduced, the difference is amazing! Too soon yet to tell if there are any mpg changes, but just the handling difference makes this experiment a success. Furthermore, it was pointed out to me that I had them too far rearward, they need "room to work". That is, moving them forward a bit would allow the airflow a little more room to get re adjusted somewhat. This made perfect sense to me, as on the airplane we put them ahead of the area we want the airflow to stay attached to, by 6 or 8" or so. So, I pulled them all off (just double sided carpet tape) and then just to make sure I wasn't imagining things, drove it on the interstate again, and, the squirrley handling was back! So, no question the vg's are doing something, and that something is good. They are now semi permenantly glued down right behind the antenna, about 6 or 8" from the rear deck drop off, and while I have yet to drive it at freeway speeds since the move, I am real pleased so far. I will report back after a couple tanks mpg wise, if it's the same I'll be happy, I'm thinking whatever is going on to effect the handling so much (less ass end drag and turbulence?) must have favorable results on the mileage, that would be a real bonus if it did.


How did you come up with the angle pairs that you used?

[Idahotom]

I used the same spacing and angles as the company I use (www.microaero.com) determined long ago to be the most benefical and lowest drag. All that ever changes is the fore and aft positioning. Note the small size....all that is needed to effect the boundry layer they claim. They provide an adhesive vinyl stencil that you simply layout and stick down, and it has cutouts so you put the vg's where the cutouts are, real quick and simple. I have high regards for this company, as do others in the aircraft world, so I trust they have this all figured out by now and just did it like they do.

I had a little time to kill yesterday, and stopped by a Toyota dealer and took a Prius C for a test drive. To my surprise the salesguy really knew his hypermiling and hybrids details. He was all excited to show me the side vgs the little Prius has, and some other little aero details that I hadn't noticed. Toyota really seems to have done their homework on that rig, pretty damn cool. But as the hybrid advantages are greatly reduced in open highway driving as compared to city driving, where it really shines, and with my rural location such as it is, the Yaris is much more cost effective. They worked me up a trade in price, 6K+ for my '08 HB with 70K+ miles, not too big of a rip off, and I was surprised at the (somewhat) low price of the C, 20K. Extremely high tech little rig, for better or worse, compared to the simple Yaris, I think I'll keep the Yaris!

[Kaotic Lazagna]

With my bro's Prius C, I get a minimum of 65 mpg (more usually in the 70's) in the city. I never drove it on the freeway yet, but when we took it out the other day, and with my bro driving (not as good at hypermiling as me), and with the AC on, he got 61 mpg over the course of around 60 miles. It's a pretty good car. Not as much space as my Yaris, definitely slower, and the HU is harder to work with, requiring you to be stationary to Bluetooth pair or enter a destination in the navi.

I had VG's on my sedan before set to the Vortekz default spacing and angles. When ever my rear window would fog up, a few minutes of driving on the freeway would create triangular clearings on the top of the window and eventually would clear the entire window. I took the VG's off (since too many people wanted to race my car and I was getting tired of that), and now I have to use the rear defroster to clear the window, so I know they definitely worked in regards to changing the air flow. I only saw .xx mpg improvement with them tho.

[nookandcrannycar]

With my bro's Prius C, I get a minimum of 65 mpg (more usually in the 70's) in the city. I never drove it on the freeway yet, but when we took it out the other day, and with my bro driving (not as good at hypermiling as me), and with the AC on, he got 61 mpg over the course of around 60 miles. It's a pretty good car. Not as much space as my Yaris, definitely slower, and the HU is harder to work with, requiring you to be stationary to Bluetooth pair or enter a destination in the navi.

I had VG's on my sedan before set to the Vortekz default spacing and angles. When ever my rear window would fog up, a few minutes of driving on the freeway would create triangular clearings on the top of the window and eventually would clear the entire window. I took the VG's off (since too many people wanted to race my car and I was getting tired of that), and now I have to use the rear defroster to clear the window, so I know they definitely worked in regards to changing the air flow. I only saw .xx mpg improvement with them tho.

Wow. If someone could consistently average 65 MPG.....and someone averaged 40 MPG in a base Yaris....the extra cost (given the figure for the C that Idahotom quoted) would be made up within 195,000 miles (or a bit less) with $3 a gallon gas --- 3000 gallons for the C and 4875 for the Yaris at the 65 and 40 MPG levels. With gas at $3.15-3.20 minimum here, and over $4.00 in parts of California, that gap would be closed in fewer than 195,000 miles. Prior to purchasing my Yaris, I tried to estimate at what point the gas savings on the standard Prius would justify the cost premium. I figured it would be at over 300,000 miles.

[Kaotic Lazagna]

Wow. If someone could consistently average 65 MPG.....and someone averaged 40 MPG in a base Yaris....the extra cost (given the figure for the C that Idahotom quoted) would be made up within 195,000 miles (or a bit less) with $3 a gallon gas --- 3000 gallons for the C and 4875 for the Yaris at the 65 and 40 MPG levels. With gas at $3.15-3.20 minimum here, and over $4.00 in parts of California, that gap would be closed in fewer than 195,000 miles. Prior to purchasing my Yaris, I tried to estimate at what point the gas savings on the standard Prius would justify the cost premium. I figured it would be at over 300,000 miles.

Yup, it's $4.03 for 87 here (bro and I only use Chevron). That car really does great on mpg. When ever I'm in it and my bro is driving, I try to teach him how to drive more efficiently. lol. It beats the Camry it replaced. Best I could get out of it was only 28 mpg, and it was a 4-cylinder model (on it's last toe about to die).

[Yaristeve]

Thanks; I'm gonna keep an eye on this thread; I've been thinking of doing the same thing. My goal is to keep the back window clean(er) during a rainstorm. I bought a rear air deflector for a Dodge Voyager van (the rear roofline has a similar curvature to the Yaris) but haven't done anything to install it because it requires a little customizing (cutting down), custom mounts, and drilling holes. Maybe a combination of both the deflector and VGs (on top of the deflector)?

You can get VGs on ebay but there is a company that makes \/ shaped VGs called Air Tabs. I was thinking of sticking those on...

[Kaotic Lazagna]

Thanks; I'm gonna keep an eye on this thread; I've been thinking of doing the same thing. My goal is to keep the back window clean(er) during a rainstorm. I bought a rear air deflector for a Dodge Voyager van (the rear roofline has a similar curvature to the Yaris) but haven't done anything to install it because it requires a little customizing (cutting down), custom mounts, and drilling holes. Maybe a combination of both the deflector and VGs (on top of the deflector)?

You can get VGs on ebay but there is a company that makes \/ shaped VGs called Air Tabs. I was thinking of sticking those on...

Do you have a spoiler on your LB?

Are you going to place yours where the OP placed his? If so, I would get the same ones he has since the size and shape may make a difference on where the placement should be. I would conduct tests like he did. I remember LT Noogie did. I'm not sure if he test videos (taped on yarn on his back window) were lost in the hack or not.

[YarisSedan]

This is interesting my yaris is so squirrly when driving it on the freeway its almost to the point where is dangerous and scary especially if its a really window day i feel if im not paying attention 100 percent on the road its going to wander to the next lane, all the suspension mods I have done have greatly improve that but if something as simple as this can make a great impact i think ill give it a try as well

[YarisSedan]

http://www.youtube.com/watch?v=We8LWkqjdX4

After watching this video i am ordering some on ebay right now lol http://www.ebay.com/itm/Universal-Fit-Vortex-Generator-Roof-Spoilier-Fins-Set-of-10-/290621728049?pt=Motors_Car_Truck_Parts_Accessories&hash=item43aa67a531&vxp=mtr

[Yaristeve]

Do you have a spoiler on your LB?

No, no spoiler. I was thinking of the factory spoiler that has a space between the spoiler and the roof. But I couldn't tell if, in that space, the air is directed downward to clean the rear window.

Are you going to place yours where the OP placed his? If so, I would get the same ones he has since the size and shape may make a difference on where the placement should be.

I really am stumped about what to do. I suppose the best first step is to install VG and see if they are effective enough at cleaning the rear window. If not, then take the next step with the rear deflector. One last concern with the deflector is how much it will mess up my gas mileage; I want to do things that increase mileage, not decrease it...

[Kaotic Lazagna]

No, no spoiler. I was thinking of the factory spoiler that has a space between the spoiler and the roof. But I couldn't tell if, in that space, the air is directed downward to clean the rear window.



I really am stumped about what to do. I suppose the best first step is to install VG and see if they are effective enough at cleaning the rear window. If not, then take the next step with the rear deflector. One last concern with the deflector is how much it will mess up my gas mileage; I want to do things that increase mileage, not decrease it...

I'm not too sure about the spoiler part, but for the VG's, you'd have to really play around with them. Their distance from the edge of the hatch and each other, the angles of each one, etc.

What is a rear deflector, btw?

[Yaristeve]

What is a rear deflector, btw?

They kind look of like rear wings except, instead of generating downforce, they just take the air flowing over the roof and deflect it downward over the rear window. Back in the 70s and 80s, before rear window wipers were available or popular, this was the "technology" to keep the rear window relatively clean. I am guessing that with tightening fuel economy rules, the rear window wipers became the standard as automakers were looking for ways to reduce drag.

http://www.andysautosport.com/toyota/1996_2002_4runner/exterior/deflectors/rear_window_deflectors/gts/gtsp00000132.html

But the Yaris rear wiper is so small, it is IMO really ineffective. Plus, all that crap on the rear after a rainstorm is really depressing to look at.

Huh! I just noticed (and read) IdahoTom's third post about the stability. I always thought my Yaris's squirrelly handling was due to the fact that it is FWD (I've had nothing but RWD cars until now) and just tought I would live with it. This alone is almost enough for me to scrap the deflector idea and buy and install VGs...

[Kaotic Lazagna]

They kind look of like rear wings except, instead of generating downforce, they just take the air flowing over the roof and deflect it downward over the rear window. Back in the 70s and 80s, before rear window wipers were available or popular, this was the "technology" to keep the rear window relatively clean. I am guessing that with tightening fuel economy rules, the rear window wipers became the standard as automakers were looking for ways to reduce drag.

http://www.andysautosport.com/toyota/1996_2002_4runner/exterior/deflectors/rear_window_deflectors/gts/gtsp00000132.html

But the Yaris rear wiper is so small, it is IMO really ineffective. Plus, all that crap on the rear after a rainstorm is really depressing to look at.

Huh! I just noticed (and read) IdahoTom's third post about the stability. I always thought my Yaris's squirrelly handling was due to the fact that it is FWD (I've had nothing but RWD cars until now) and just tought I would live with it. This alone is almost enough for me to scrap the deflector idea and buy and install VGs...

Ah, looks like duckbill spoilers. lol.

Yeah, get some and just play around with the settings until you get the yarn strings all flowing straight and not erratically.

[malibuguy]

I put Vortex generators on my Tercel track day car...mainly to clear off the back window whens its raining. Can't see just about anything before I added them...after anything above 45mph my back window is dry! Have not noticed anything on the track in terms of better stability or anything like that.
http://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-ash3/542751_10151502698910278_1589312174_n.jpg

[Yaristeve]

Bumpity bump - any updates?

Also, I was wondering if those "shark fin" style VGs could be used in V-pairs like the OP set up on his. I assume the V-pairs is to create two counter-rotating vortices?

thanks

[alfredyeez]

http://www.autospeed.com/A_3058/cms/article.html

[Idahotom]

A quick update: no big change if any, either up or down in MPG per tankfull as near as I can tell. BUT the vastly improved straightline handling continues! I actually got it up to the extremely high speed (for me) of 78 mph the other day and it still tracked great "like it's on rails".

The other neat thing is they just look cool, and they keep drivers behind me at a red light entertained wondering what they are and what they do.:w00t:

[Mittelklasse]

Yeah. I was a bit disappointed there. My 2 tanks since the installation didn't return any higher MPG.

Oh well, come to think of it -- I was driving faster than usual too, since my car has been more stable. :biggrin:

Right now I've removed them and I'm planning to install small ones on the side of the back end instead.
I saw the new Camry Hybrids have them.

http://www.toyota.com.au/static/images/16dmk-camry-rear-headlights-940x529.jpg

[Idahotom]

I think you may want to move those forward. The picture I posted was my first spot, but then I moved them forward to right behind the antenna. The theory being the vg's need a little distance to effect the downstream airflow. Just a wild ass guess, no testing! But mine are now glued down right behind the antenna, In the aircraft world, somewhat the same deal, they are put a bit ahead of where you want the effect most. The good thing about the double sided tape is it's easy enoguh to try a few places, and yeah from a practical standpoint further forward is better re: hatchback opening!

[malibuguy]

well i'm new to the Yaris and this forum so I will keep it simple. Read up on the VG's and thought I would give it a try. I have a 100 mile commute everyday and want to maximize MPG.
So I had some scrap 1/2"x1/2"x1/16" angle aluminum in the shop and thought I would try that first.
http://www.yarisworld.com/forums/attachment.php?attachmentid=51284&stc=1&d=1373130395
used 3M hanger double sided tape to attach themhttp://www.yarisworld.com/forums/attachment.php?attachmentid=51285&stc=1&d=1373130395
marked off even spaces for a total of 12 VG's.
http://www.yarisworld.com/forums/attachment.php?attachmentid=51286&stc=1&d=1373130395
used a protractor set at 18 degrees for the correct angle. Somebody correct me if i'm wrong as that's what I read is the best angle to use.
and installed them.
http://www.yarisworld.com/forums/attachment.php?attachmentid=51288&stc=1&d=1373130395
This was just a first try as I soon found out this is a bad spot as the rear hatch hits them. Also not to sure there current location is effective as its after the break for the rear hatch and I may move them forward. Also may up the size to 1"Hx2"L. but this is what I had lying around.
noticeable changes? Not really but the rear end did seem more stable when cornering at speed.

Damn drive a yaris in md and have a long commute to fabricate...we must be brothers.

[Yaristeve]

After being batted around like a ball of yarn in a kitty's paws today due to the wind, I was reminded of this thread and wondered if anyone had any updates...

[Klink10]

This interests me also.

[Idahotom]

Mine are still doing their thing, no mileage increase, discernible anyway, but much improved straight line tracking. A very strong direct x wind can still move it around a bit, but even that situation is improved.

[Yaristeve]

Mine are still doing their thing, no mileage increase, discernible anyway, but much improved straight line tracking. A very strong direct x wind can still move it around a bit, but even that situation is improved.

Are your VGs the smaller 1" X 0.4" ones or the 1.5" X 0.?" ones? I noticed that ebay started a aircraft section in their ebay motors and there is an auction for the smaller size VGs.

[Idahotom]

Mine are the smaller ones. Bigger ones are not more effective I'm told, as the layer of air you are trying to control is .1 of an inch. Bigger may look more effective but there is a reason they make the small ones the size they do.

Having said that, I know the aircraft supply company I got mine from for my plane (MicroAerodynamics) DOES supply larger ones for use on the horizontal stabilizer, in front of the elevator. They make the elevator more effective at slower air speeds, like right when you really need it, landing. I only had enough of the small size left over from the plane install, so that's what I used on the Yaris. They make such a difference in the straight line stability, work so well in other words, I'm glad I didn't use the big ones.

[Yaristeve]

Thanks. I guess I will try them out...

[Rodger Wilco]

Yeah i dont think that you will get much more MPGs out of the VGs but I bet that it keeps dust off the back window more. I cant imagine that adding drag to the surface will increase your efficiency. On aircraft they delay airflow separation (as you know I am sure), but they also add drag.

Help me understand what benefit you would be getting out of them on the yaris, other than looks?

[Idahotom]

Increased stability at highway speeds (60 mph +) was my result, as noted. A dramatic difference, especially I had them taped on first while testing, drove for a week, then took them off and drove another week. All these miles on my usual well known route, that features several flags along the way to keep me informed as to any wind. This increased stability is especially noticeable when along a semi.

I didn't do it for looks, that's for sure. My mileage has stayed the same, no better no worse, and I keep real good track every fillup. My guess is the very slight extra drag is offset by the apparently cleaned up airflow on the ass end. Getting back to the looks thing, not my reason but now that I feel what they did for my car anyway, yes it does give people behind you at a stoplight something to cogitate over!

[WeeYari]

Your original pics are dead. How about some new ones since this thread is seeing a resurrection.

[Idahotom]

Crap, those pictures are history I guess. I'll take some new ones and post them in a day or so.....

[Idahotom]

new pictures.....http://i649.photobucket.com/albums/uu213/simkot/tires002_zps516dfc2c.jpg (http://s649.photobucket.com/user/simkot/media/tires002_zps516dfc2c.jpg.html)
http://i649.photobucket.com/albums/uu213/simkot/tires001_zps29601ee6.jpg (http://s649.photobucket.com/user/simkot/media/tires001_zps29601ee6.jpg.html)

[dragoonmc]

Those are tiny little things

[Idahotom]

As big as they need to be, no bigger. And, the pair spacing may seem far apart, but that has also been deemed adequate by extensive testing. The boundary layer they influence is measured in a fraction of an inch, 1/16" or so, that word is from the airplane people who came up with the these in the first place. Those great big ones real close together are something dreamed up by car people, not airplane people. They may LOOK more effective but may not be.

[Yaristeve]

Doesn't the base of the antenna mess up the airflow to the middle pair? It would seem you would want two pairs of VGs at either side of the wake from the antenna base? Or, am I "off-base"? :D

[1.5]

I was going to ask the same question ^^^

if you say only the tiniest VGs are needed in the right spots to change the air flow significantly, then that antenna must be in there F**king the entire thing up since its so huge in comparison.

[Idahotom]

Well... I wasn't about to move the antenna, or change the VG pair spacing. Keep in mind I had a stencil that came with my vg kit, and all you do is position the stencil and then glue a vg where the stencil is cut out, this real simplifies the layout and makes it idiot proof. So, after shifting the stencil side to side, this is what I came up with, probably not optimum, then again that antenna base is nicely faired so it may not be disrupting things too much.

This was a half ass experiment anyway, largely based on the fact I already everything I needed left over from the plane installation. The real surprise to me was, half ass as it was, how it changed the car straight line tracking. For 0 money and an hours time I got great results, and am not real motivated to mess with anything now. A smoke generator rigged to the cars front end (up on the roof front so it wouldn't blind the driver!) somehow, and a video camera aimed at the rear end, would be the real way to determine what was going on, I got lucky it seems.

[scratchpaddy]

Just read through the whole thread. I hope it's okay to bump an old thread like this. Thanks for writing out what you did, Tom. This is so awsome! I'm going to print some up to try on my car. I even have blue ABS plastic to go with my car. :biggrin:

I did notice that the Yaris is more squirrely on the highway than even my Metro. I assumed it was the quicker steering ratio compared to the Metro's manual rack. This is definitely worth a try.

[dogsridewith]

Might try adding little generators like that on the tumblehome area between the backseat side windows and the rear window?
Bringing this over from a thread in Cars for Sale:
"I once drove some 300 miles on PA interstates covered with inches of snow because road crews were off for Christmas day. Sharp skinny 155-80/13 tires (new, but not aggressive tread pattern) on 89 Tercel EZ Hatchback w/ rear seat removed. Car wagged it's tail continuously at speed, which was disconcerting until I determined it was otherwise well planted and controllable. There were SUV's etc. that ran off the road every mile or so. Maybe 2 vehicles passed me the whole day."
(Vortex street shedding Tercel tracking instability generators)

[SirDigby]

I've been looking at these on all new cars when I walk around the lots. there seems to be a lot of them on mirrors, under the front bumper, and on the tail lamps. I wonder why they don't put them on the roof? (besides the giant fake ones)

[Idahotom]

I mentioned in another thread, since buying a 2013 Pirus plug in, I was selling my Yaris. After several of the usual selling a used car tire kickers that just wasted my time, the eventual buyer met me at my crane yard, where I had the Yaris on display. Turns out, after he noticed my "IDAHO, A PILOT'S PARADISE" license plate, he was also a pilot. And even before I brought his attention to the VG's on the rear, I knew that would be the hook to make the deal. It was, he bought it!

Yeah, lot's of interesting little aero details on the newer cars, if one knows what to look for. When putting a trailer hitch mount on the Prius, I was underneath it and noted that the rear bottom is nice and smooth, covered with a molded plastic thing. Two protrusions stick down a bit lower then the rest of this panel, providing the needed clearance for some chassis bolts, maybe the shock mounts. Rather then just cut holes in this bottom cover to get the room they needed, the Toyota engineers had provided perfectly streamlined bumpouts of the same plastic material, that got the job done with little or no extra drag.

This minor detail, underneath where no one would ever notice, blew me away! They probably reduce the drag some fraction of a tenth of 1 percent overall, but they did it anyway, you have to admire that fanaticism in such a small detail! BTW, I just completed a 3000 mile road trip, and averaged 51 MPG, plus slept in the car overnight twice with the heat set at 68 degrees. The ICE would kick on for about 1 minute every 15 or so, fuel use was such that on 3/4 of a tank, I could have gone several days like this, it's an amazing car, even better then I had thought. Prius campers, I have found out, are somewhat common, as you have built in climate control both summer and winter. Slide the front seats forward, flip the rear down, slide a light plywood deck forward to fill the gap, and nighty night!

[SirDigby]

these things must work. they are putting them on golf clubs..
http://www.prnewswire.com/news-releases/new-micro-vortex-generators-create-faster-clubhead-speed-for-greater-distance-in-the-new-wilson-staff-d300-woods-300387463.html