Aerodynamics - Performance, and Economy?

[bones33]

Here is a link to an interesting article on aerodynamics and what each type of aerodynamic aid does. http://www.autozine.org/technical_school/aero/tech_aero.htm

Most vehicles pay at least some attention to smooth shape, probably to reduce wind noise near our ears more than anything else. Interior volume, looks and utility as a vehicle play a larger part of the design than aerydynamics. What I find most interesting is that almost all vehicles have horrible underbody aerodynamics. While they may look slick on top, the underneath has lots of aerodynamic losses. Cars are lower to the ground than trucks so it may not have as much gain, but SUVs and pickups are absolutely horrible under there where there is more significan air flow. It seems this would be the next easiest place to look for gains, especially for SUVs and trucks.

[Matt Timion]

Very good article. I saw on there that the Ford Probe V was the most aerodynamic car ever made.

More about it here:

http://www.scottgrundfor.com/concept/1985probe.html







Too bad it's a concept car. That would be an awesome EV car.

[SVOboy]

Damnit! My car almost made the drag world record chart, I'm at .29, I guess it's time to do some modifications to get one there. There's a pretty good thing on here about how to do an experiment to calculate drag. Hmm. Very interesting article.

[MetroMPG]

funny this topic should come up today. i was just calculating the frontal area of my car to plug in to some drag formulas.

in my opinion, after driving style, aero mods are the area where the largest gains in efficiency can be made for the least money spent.

if you haven't read about Phil Knox and his aero-modded Toyota T-100 pickup, you should. a real-world example of how he increased his hwy mileage by 28% without fiddling with the engine one bit.

free fuel riding on the wind - EV World

admittedly, it's relatively easy to improve a pickup truck's aerodynamics, because they suck to begin with. improvements to a modern sedan or hatchback will be less dramatic, but it can still be done.

i tested 2 aero mods on my firefly late this fall and they netted me a 5.7% increase in hwy mpg in repeated, controlled testing:

Testing grille blocking & wheel skirts: +5.7% improvement - metrompg.com

aero mods will be my main focus next spring & summer. still on my list:

"permanent" mods:

- full under tray
- gap fillers in front wheel wells
- ride height lowering
- deflectors ahead of each tire

"experimental" mods:

- a removable lightweight boat-tail for hwy trips

i expect the "permanent" mods (in addition to gains already realized from rear skirts & grille blocking) will net a total hwy improvement of around 15%.

the boat tail idea is the least practical, but the rear of any vehicle is actually where the biggest gains are to be made (reducing the wake area).

svoboy: phil also owned a 1st gen crx which he aero modified extensively (extended the rear of the car by 12 inches so he could continue the taper to reduce the size of the following wake). he both increased his top speed (tested on the salt flats) and his hwy mileage dramatically.

there's a yahoo group (maxMPG) that focuses pretty heavily on aerodynamic discussion:

http://autos.groups.yahoo.com/group/maxmpg/

[SVOboy]

Phil, eh? I'm actually a second gen crx owner, and I think they're a bit better on the aero bit of it, not sure though. How did he extende the end? Fiberglass? I think making rear wheel covers is a good idea, but we need someone with fiberglass skills to work on that. I should pick some up from an art project I'm doing (I hope).

What did you mean by deflectors though?

[Matt Timion]

I just read that Phil Knox's CRX managed to get 84.5 mpg. Now I need to see a picture of it.

Maybe I'll email him and ask for pictures, etc.

If you guys are interested in sub-dividing the forums into more subject specific I can do that. I don't, however, want to go too crazy with the subdivision.

[SVOboy]

Only thing I can think forum wise is to move this stuff back to general, since it's basically the same stuff, and the two with talking confuses me. But leave the DIY open. Or lock the articles so they can't be replied to and it's more of a repository.

Anyway, 84.5 mpg on a rex! W00t, I must see it now.

[MetroMPG]

i think he did it with fiberglass. warning: if you don't think my firefly is "cute", you're not going to like what he did to the crx.

it's not pretty (i don't mean the workmanship), but it's clearly more aerodynamic than what honda did.

join the maxmpg group and you can browse the photo album. there's a couple of pix of it in there - and tons of other aero related stuff.

if you don't want to join, let me know and i'll go fetch the pic and post it here.

d

[MetroMPG]

Originally Posted by SVOboy

What did you mean by deflectors though?

the insight actually uses front and rear deflectors. note: they don't span the whole width of the car; they're just in front of the tires.



as does the new porsche cayman, below. (except the cayman's deflectors are just black plastic slats, whereas the insight's are shaped/molded into the bumper and rear rocker panel area ahead of the back tires.



and look closely at the front of the middle pic of the probe concept that matt posted. you can just make out that the shape of the front bumper ahead of the front tire is several inches lower ahead of the tire area compared to the level of the rocker panel behind the wheel. there's a more subtle one ahead of the rear tire too.

these deflectors are turning up on a lot of new cars. mostly the flat slat style (cheaper, and easier to replace if crunched on cement parking berms, etc.)

matt: i'm okay with the number of forums. i never pay attention to which forum i'm in anyway (unless i'm starting a new thread) - i just use the tracker page to see what's new, and click in from there.

[diamondlarry]

matt: i'm okay with the number of forums. i never pay attention to which forum i'm in anyway (unless i'm starting a new thread) - i just use the tracker page to see what's new, and click in from there.

That souds like what I do. I keep a browser opened to the site at all times and click refresh every once in awhile.