External air curtains
 

Throttle stop drag tested, tuft tested and pressure tested. The most effective 'simple' modification for measured drag reduction that I have done.

https://www.youtube.com/watch?v=lSN2vQE_WPs

The best candidate I've seen, from Ecomodding Central. I suggested he search on 'edgarwit':
https://i.gyazo.com/79057290b82dffb3...01cc2a8e68.jpg
https://ecomodder.com/forum/showthre...eas-38904.html

Awesome.

I appreciate you trying new things and testing them rather than dismissing them as something only large corporations with vast resources and staff of professionals can do.

And why does it look so ugly? The modifications must be applied in such a way as to be related to the current design of the car. It's like they're taken from the truck ...
I would have chosen the solution inspired by Mercedes-Benz A-Class/C-Class.

Well when you do so, you can show us the results.

That's a section of aluminum extrusion. I consider it proof of concept.

It is totally useless in this case. An aluminum (or any other material) sheet does the same thing.

You'll have to show us the results of your testing - this is an interesting area.

Vman455 told me he used sheet metal for external front air curtains and recorded a drag increase on his Prius - but they gave much better stability when passing trucks.

As I say, I'd love to see the results of your tests.

Yes, this is correct--the sheet metal front ducts by themselves appear to increase drag based on fuel economy testing. But when I compared pressure difference on each side of the car just behind the front wheel arches (at Julian's suggestion--thanks!), I found that the average pressure difference between sides in a 25 mph crosswind was nearly 15% lower with the ducts on. The wing sections seem to be a better solution, and something I'll probably try in the future.

Can you post a comparison of the two approaches?

I speculate that a flat plate would have critical angle-of-attack and positioning criteria. I further speculate that a curved plate would approach the result of the airfoil section.

I've been thinking about air curtains on a Geo Metro. It looks like I could add a partial diverter on each side (flushed out to the upper bumper) with curved plates capping the void created.

'product' safety
 

I just wanted to remind all that if you're operating on public roads, please be mindful of pedestrian traffic, and what might happen should you accidentally strike one with your external mods. 'Slicing and dicing' shouldn't be a component of aero mods.

I don't have to prove anything, all the manufacturers that have implemented have already done that. The outer edge is the thickness of the spoiler material.

In the real world: we'll keep on testing results of real modifications.

But if you can cite any tech paper references, I am certainly interested.

Can you?

There is a lot of 'tech paper references' on the internet if you are really interested.
Your world is not as real as you think.

I am curious what the authorities think when you make such changes to a car and drive it on public roads.

Wonderful! Do you want to link to them?

Mmmm. Maybe I don't live where you live?

Good point, perhaps next step would be an attempt to incorporate air curtains into the existing bodywork using similar principals.

That is to say, place the airfoil inside of the bodywork with an opening in front.

Where this may get tricky on modern cars is the wheel well liners that older cars lack.

Dremel makes a few tools that may come in handy for such a task.

Knowing where the airbag sensors and wiring are on your particular car will be a must.

authorities
 

Aerodynamic modification for fuel economy has been encouraged by the U.S. Department of Energy, since 1973.
Rear elongations of up to 60-inches are authorized for a solo vehicle.
TV/ Trailer combinations would be GVWR-limited. Aerodynamics is fair play within that parameter.
Sometimes the state police and highway patrol will 'take a look' but I've never been stopped for mods.
Since we share the road, being mindful of other's safety is a good thing.
OEM air-curtains are typically 'embedded' 'within' the body, where they won't shred the flesh off a pedestrian or cyclist should something go wrong.
That's all I was eluding to.:)

The front-facing elements of my air curtains are pretty pedestrian friendly. The leading edge of the aerofoil is quite rounded, and the end plates have had their edges rounded. The whole assembly would break off on impact - much more likely to be with a kangaroo than a person, where I drive!

:thumbup:

The problem is that others will take it as a good idea and apply it in another country ...

The airbag sensors have not been mounted in the spoiler for years ...Most of the manufacturers use the material from which the spoiler is made as the outer edge and apply only a U-shaped air guide inside.

In such a case the problem would be with the country, not the air curtain.

Do you think that circular fog light holes would be sufficient for internal air curtains? I have been thinking about doing this to my Camry.

I am not sure if enough velocity could be maintained for it to be effective since the air will need to "change shape" to exit through the wheel wells.

Very easy to find out if the duct will flow plenty of air.

Use a differential pressure gauge (eg Magnehelic) to measure the pressure in the fog light opening and the pressure in the wheel arch where the opening would go, at say 60 mph. You want a decent pressure difference (eg 0.5 inches of water), with the higher pressure in the front opening.

At a pinch you could do it with a home built manometer at basically no cost.

Don't worry about the change in shape of the duct - if there's enough pressure difference, there will still be plenty of flow.