AirTabs shown to work by respected EM member
 

AirTabs shown to work by respected EM member.

AutoSpeed - Fitting vortex generators to a three-box sedan

Suck it haters!!! ;)

3% improvement based on "I'm getting better mileage."

Let us know when he rolls it down a mile long hill 20 times or so with and without the Gimmicks installed and gets a positive result.

Otherwise....

http://i40.tinypic.com/1z166mb.jpg

Why does it always seem that people who use the term... "haters" show a complete lack of acceptance? I asked a girl a simple question and she went on a tirade about me... "hating" when I had not expressed any opinion whatsoever.

Moral of the story... don't ask girls why they weigh more than you.

I believe that the expression is "Mind blown."

How did you know?!

Okay, I just spent a while trying to find the messages so that I could quote myself directly and not rely on my memory, but the trouble started when I asked "I hope that you do not mind me asking, but why are you on a dating site if you are married."

This may be off-topic... :D

When it comes to vortex generators....anything to distract from the ugliness is a blessing. Relationship issues? Bring em on!

I wanna know, how do I keep my cat from rolling in the dirt and getting filthy?

http://i49.tinypic.com/29gol6t.jpg

He is getting 3% better mileage. That equates to about a 6% reduction in drag. Further more he keeps detailed logs of his mileage and he is getting consistently better mileage than he has ever achieved.

If you would like Julian to try another test just ask him.

Otherwise....
https://ugandaninsomniac.files.wordp...ck_it_img1.gif

I see a problem here.

I did not add vortex generators to my car, but I did get a better mileage quite suddenly. See my record.
Part of it may be explained by better use (or rather, disuse) of the hybrid system, though some other member here on ecomodder is adamant it can't be proven like that.
Other factors like weather - no, was consistently cooler than usual for the time of year for the last 4 months. Spring is late over here.

If a 3% improvement in fuel economy goes as proof, then it seems I have carte blanche to claim whatever I like to have a positive effect on FE.
Now what did I change to my car and habits those last 3 months?
I changed location at my office. I replaced my wife's Ipod with her music by a 32GB USB stick with mine. I got several dents and some glass damage from stone chips from our frost damaged roads. The car steadily got dirtier. I installed some LEDs, and do in fact use the headlights less now.

The gain from the LEDS is easy to calculate; it is about 1% at most. So if you want good FE, take my advice and move that office chair, enjoy your music, stone your car and whatever you do don't wash it! :D

I'm not saying vortex generators don't work. In fact I hope they do. But variations like these can have so many reasons that it becomes impossible to prove it with just 1 car by just keeping fuel records.
If they do work, they deserve proof that goes beyond this, and a nice picture.
This one goes without words.
https://i.chzbgr.com/maxW500/7344596224/h8B01D5C3/

(ps. did I mention change the interior? This one is bound to have some effect on FE, for better or for worse...)

Dont tell anyone but I got a thing for hello kitty. ;)

Your secret is safe here ;)

Supposing it does work... It may work best at that specific angle, making results difficult to duplicate for others.
Or they might have even better results with a small kammback instead

I don't see any A-B-A. Anyone purporting to have achieved something as small as a 3% gain had better be using testing protocol that can detect 3%. :rolleyes:

I agree, yet I see consistent claims about better trailer behavior where AEROTABS are installed. However much improvment in FE may be present is also open to driver skill (the hardest to quantify). The big truck industry pits drivers of the same company against one another to establish the range of possibility. And that difference is nearly 30%. 3% is hard to tease out.

IOW, I'd try the -tabs on a trailer (and may) and not consider it a waste if the trailer exhibited some better behavior in winds. Around $220 for a kit.

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...http://i.imgur.com/4Z0Z6LT.jpg

I do not feel like I have contributed much to this forum, even though I spend tons of time here. At most I kind of sort of slightly remember something that I read in one thread sufficiently to find it again sometimes. I did try to marine-shrink my hubcaps, but since they are the bolt-through type, that was doomed to failure.

You need to attach them somehow.

I still have one idea that I will try after finals.

I am reminded of the expression that some people exist to serve as a lesson to others and I think that I have provided some entertainment on occasion. I was thinking that this was something that I could do, just have you guys decide how to scientifically test them and I would do so.

I could record myself reading my notes and then loop that, or something.

Honestly, though, for $220, I just do not see the return on investment. That would be like replacing stock rims with ones that weigh negligibly more, but might be more aerodynamic.

Wow, that's a beautiful cat! Thanks for sharing. (I can't have a kitty because I'm terribly allergic - Well, I have had them, but I suffer terribly)

Relationship issues... maybe fit for a drag queen?
This is bound to cause a stir!
https://i.chzbgr.com/maxW500/7405277440/hD5B667E0/

Honestly, though, for $220, I just do not see the return on investment.

If you understood that trailer behavior is a concern every foot of ground covered, then the price is cheap (if the benefit is forthcoming). Trailer "wander" causes the need for steering correction. Clear, now?

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It has been a while since I have driven a trailer. I just know that I hate backing up with them.

That makes sense, however, I would not purchase air tabs, a trailer, and a trailer hitch, just for some A-B-A testing, when I would not know what to do with the trailer afterward.

Agree completely with Frank.

Julian Edgar has done a lot of really great stuff. But I take issue, respectfully, with the quality of his testing. It's just not on par with his admirable level of DIY & his good writing.

I'm pretty sure I annoyed him on this forum by saying that in another thread he was participating in.

Maybe there's some way we could lure him into this thread. I haven't seen him since he was promoting his book.

He must be busy with groupies.

And I was too sharp in my reply. If trailer behavior improved I would consider it money well spent. And potential FE benefit might be from that effect alone (less trailer wander + fewer steering corrections).

3% on a solo car hardly seems worth it, proven or not.

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slowmover -- There's something I've been wondering...

Suppose the trailer had a retractable skid at the rear, and some feedback loop that fed off the difference between the angle of the front wheels and the angle of the tongue at the hitch. Wouldn't judiciously applied drag cause the trailer to fall in line behind the hitch?

If the contact pad was titanium, as a bonus you could throw sparks at any tailgaters. :)

Good ole iron works too for that. I'd never buy a motorbike that doesn't have a center stand that you can push down while riding it ;)
Only did that twice afaicr, and in both cases with good reason...

Sure, why not ?

If you change something and you get better FE, see previously impossible MPG values, then the change has had some effect. Like it or not.

Is it 3% ?
Probably not - that'd mean about 6% drag reduction, which is fairly massive.
But it's clear that the flow pattern HAS been changed by adding the VGs.
It's at the rear, so it'll likely bring something, too.

I've had tiny VGs on Hägar - mirror and A-pillar.
Merely 1mm or 1/25th of an inch high, but they also changed the flow pattern on the side windows and quietened the A pillar noise .
Nothing quantifiable in the MPG department though.
They were too small to do anything at the rear end though - where I had them around the entire rear hatch (station wagon).

VGs work.
They wouldn't be on gliders if they didn't.
It's just a bit tough to get them positioned so they really work for you, and to quantify it.

The traditional spots to put them obviously didn't work here.
Moving them to be a tad ahead of the separation point did work - which is exactly where they are on gliders ...

Are you willing to put your head on the chopping block for each and every A-B-A test that has ever been done by EM members ?

MetroMPG was quite obsessive about them :)
So we expect his results to be close to reality.
But was everybody else as committed ?

I ain't saying they cheated or something, but folks were regularly testing in conditions that varied beyond their control.

A couple degrees warmer or colder, would have meant a lot of difference to my V50 when it was right about its most sensitive temperature.
Extensive testing can take longer than it takes the sun to heat up the testing environment ...

Wind speed, wind direction are beyond one's control.
Even if there's hardly any wind, there's usually some wind.
And it ain't always coming from the direction the weather guessers claim it will, nor is it always coming from the same direction.
But who's been testing with a wind meter giving both speed and direction ?


3% is hard to detect even in A-B-A testing
On my new car the smallest change on the display equals 4% ...

What about A-B-A with zigzags on your mirror and A-pillar. The MPG difference might not be quantifiable, but doesn't moving air make less noise when it is attached?

Make a bunch of zig-zags and run a narrow strip of tape behind each of them. Then you could do A-B-A-B-A forever, putting zig-zags just ahead of the strip, and measure wind noise.

Absolutely not! I know testing out in the elements is dicey at best. I know my efforts at testing would be as well, and that is why even after all these years you do not see me making fe improvement claims from mods or techniques. The best I can do is report on trends after enough samples have been collected. As I said, if you are going to make claims that you have identified a change of a couple of percent, your testing needs to be robust enough to have that fine a resolution.

Don't forget... there's no free lunch. It takes energy to generate the vortices. So the effect of improved downstream airflow that may be revealed in tuft testing has to be greater than the cost of the vortices themselves to see a net efficiency gain.

Gee Frank, you're getting all serious and stuff.

I've been thinking about Gerrelt's Garage -- Reducing Windnoise / Raingutter Fillers and Gerrelt's Garage -- Vitaloni California mirror on standard stalk.

Do you have a search term or reference link?

Don't worry- it'll soon pass! :p

Manually slam the trailer brake control and nail the throttle. Since the first days of trailer brakes.

There have been some other electro-mechanical devices tried over the years, but Americans and the DOT has little interest. In Europe there are a few electronic devices now in place to correct sway (but the geometry of how they do the lash up is different, and predicated on some different assumptions about towing).

Sway is a subject rather past a bit of tail wagging. All trailers do it, it is only how much. A fair sized grey area, overall.

Titanium sounds fun, but wouldn't magnesium be MORE fun?

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Would it be possible to kill the sway by coupling the wheels together, like when using a diff lock?
If the wheels on both sides are forced to turn at the same speed that would kill the sway.
It better be unlocked in tight corners though to stop it from killing other things than sway.

EDIT never mind, wouldn't work. The trailer would resist changing direction, pulling the towing vehicle sideways thereby inducing rather than killing sway.

i think everyone missed the part of the manufacture website that says they only do something over 35mph(60kph)

so who here drives 35 or over in a city(without pulse and glide) ..... me thinks they suck back more then they give.

Here I am back again - only just saw this thread.

I agree that an A/B/A test would be more valid than what I have done.

But also a bit more on the background. I live 80km (50 miles) north of Canberra, Australia. I drive into Canberra and back 2-3 days a week. There is no traffic - I don't even reach a traffic light until about 75km into the trip. Sometimes I see only 5 cars in the first 50km.

It is just an empty country road driven at a constant speed - 100 km/h.

I also drive from here to Sydney and back - freeway all the way (it's about 250km each way, with only the final part in city traffic).

I owned the car for about 10 months before adding the vortex generators.

I know the fuel economy on these trips very well. I can immediately see by the fuel economy if my wife has filled with 95 versus 98 octane, and I can see the difference in fuel economy that my 0 degree C mornings are having. (40 degrees C in summer, 0 degrees in winter.)

The fuel economy has never been as good as with the vortex generators fitted. Never.

Now: here's the joy for you sceptics. I had a cam belt change at 100,000km, about 2 weeks after I fitted the vortex generators. I saw the improvement in fuel economy straight after I fitted the VGs, but the confirmation over the 10,000km since has been with the cam belt changed and the VGs fitted. So perhaps some of the improvement is that cam timing is changed a fraction, i.e. belt stretch is no longer there? To me it doesn't seem likely, but it is possible.

Oh and the kit price people are quoting is for heaps of the things. I think mine cost me a few dollars each - but I did buy them years ago.

As much as I blather about A-B-A tests, I wouldn't rule out long distance (and also long term) testing as a way to measure meaningful trends in fuel economy... provided it's a big sample.

There are a few members here who are meticulous record-keepers (recording the results of every single commute, both ways, with environmental and other info as well) who can spot a deviation from the norm just because the sample is so good.

But even a big sample can give warped data.

Take my fuel log (sorry to repeat myself from page 1); up to a point all fillups were worse than 50 mpg, after that all were better.
It was not the weather (it kept freezing for months and even now the temp averages below what it was when I got the car in October). It wasn't driving style (or so I believe). It wasn't the HIDs or LEDs, It certainly wasn't VG's.

So what does that prove? Nothing but that fuel logs are an indication, probably, but no certain proof of the effect of a modification.

AirTabs
 

Julian,forgive me,as I'm quite late to the party,but can you please tell us the kind of car you're driving?
My mind was thinking in the direction of a notchback.I wanted to make sure.Thanks!

Julian E. -- I believe you. But then I simutaneously believe in 'gut feelings' and 'confirmation bias'. :)

Are you familiar with the work of Yoshi Suzuka? He's been at it since the mid-70s, like you and aerohead, and talks at one point about up to 1500 component tests a month, using miniatures for preliminary work before moving to the full scale tunnel for fine tuning, and how power required grows with the cube of the volume of air (or something).

Late one night, in a certain frame of mind, I got to thinking about wind tunnels with multiple propellers needing diffusers to smooth out the resulting flow and I wondered—why not paddle wheels? I did this and posted in another thread:
http://ecomodder.com/forum/member-fr...6-12-26-10.png

More lately, I'm thinking only two wheels, at the 'stern' and shorter, thin walls with fillets that concave up against the sweep of the paddle wheels.

Less turbulence? On-topic for air tabs?