AirTabs shown to work by respected EM member

[freebeard]

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

[Xist]

Originally Posted by freebeard

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.

[slowmover]

Originally Posted by Xist

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.

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.

.

[freebeard]

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.

[RedDevil]

Originally Posted by freebeard

...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...

[euromodder]

Originally Posted by ChazInMT

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

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 ...

[euromodder]

Originally Posted by Frank Lee

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%.

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% ...

[Xist]

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.

[Frank Lee]

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 ?

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.

[MetroMPG]

Originally Posted by euromodder

VGs work

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.