Suggested Aerodynamic Mods for a Cobalt - Page 7 - Fuel Economy, Hypermiling, EcoModding News and Forum

aerohead · 06-13-2009, 05:41 PM

Quote:

Originally Posted by stevey_frac

Ok, so i was thinking about this. I think i can build a basic metal frame that attaches to the axle, and the little air foily bit that hangs off the back bumper. V1 would be covered in Coroplast. If it offers gains, V2 would be covered in aluminum sheet metal, and painted either black, or the same color as the car.

For some reason it feels like i'll be increasing the wake though, and that there will be 'more car' that the low pressure 'wake' will be 'pulling' back.

also, if i can get some sharks with frikken 'lazers'...

Steve,I think that the "wake" already reaches well under and towards the front of the car underneath.The bellypan typically won't increase frontal area,and the angled diffuser actually does reduce the wake area,and increases the pressure there.Both good things.--------- A quick and dirty way to think about aero,is that the first 33% of an ideal vehicle is used to accelerate the surrounding air from zero,up to the speed of the car,then the last 2/3rds of the car is used to provide a gentle ramp for the air to slide back to where it was before you came along.Ideally,it requires quite a "back" on a car.That's where the "teardrop" comes in.When we fashion cars to be more like the teardrop,we approach zero profile drag (the largest component of aero drag) and highest mpg.

stevey_frac · 06-13-2009, 08:08 PM

Currently in building my air dam! it's gonna be 3" deeper then stock in the middle, and 5" in front of the wheels. I think it'll look good.

stevey_frac · 06-14-2009, 11:29 AM

Pics of the air Dam. The edges didn't go together as well as i'd hoped, but overall it looks fairly good. Cars seems a bit quieter. This next week of driving will tell how much improvement, if any, that i see.

-Steve

stevey_frac · 06-15-2009, 07:45 PM

So this is just first trip impressions but it's definitely an improvement.

The drive to work was faster then normal. I rarely was blow 60 MPH. I was using the air conditioning about 50% of the time, and I still managed to pull a fairly impressive 4.9L / 100 km. That style of driving would typically land me in the 5.5L / 100 km region. In addition, i'm at the end of my oil life, and because of the driving I do, the oil thickens as it ages, so I expect when i do an oil change later this week, that I should be able to post better numbers.

I think this might warrant some more rigorous testing!

I'm also still considering the diffuser. I'd actually kinda like to make one that is actuated to lower at highway speeds, and raise in the city. o.O. The engineer in me (read: geek) demands it! :P

-Steve

Istas · 06-15-2009, 08:11 PM

Definitely want to have the front panel overlapping the side ones, rather than the inverse like you have it. Other than that, looks pretty good! Keep up the modding.

stevey_frac · 06-15-2009, 11:35 PM

They are actually but joints, but they don't line up perfectly. It's hard to photograph properly.

stevey_frac · 06-20-2009, 01:04 AM

I took the air dam off. It was too low, and was scraping, and looked horrible. I'm gonna cut it back to 3" from 4.5" and not extend the pieces in front of the tires. Instead i'm gonna have separate deflectors in front of the tires.

I got my oil change done, and that helped a bit. And i'm still considering the diffuser. If my reading is right, the diffuser is basically supposed to be an ideal nozzle in reverse, slowing down the air, and getting the pressure back up, and keeping the renolds number lower to maintain laminar flow.

.. Some of my fluid dynamics courses are coming back to me!

cfg83 · 06-20-2009, 02:21 AM

stevey_frac -

Quote:

Originally Posted by stevey_frac

I took the air dam off. It was too low, and was scraping, and looked horrible. I'm gonna cut it back to 3" from 4.5" and not extend the pieces in front of the tires. Instead i'm gonna have separate deflectors in front of the tires.

...

I thought it looked good. Looking forward to pix and results for V2.0.

CarloSW2

stevey_frac · 06-20-2009, 11:35 AM

I should qualify that. It ended up looking bad because it scrapped so badly, it had scrapped the paint off of most of the bottom half inch. Hence the desire to trim it back, and hopefully it won't scrape.

I also lost of one the side panels! I hope i didn't loose it on the 401. I can't imagine a bolt to the head would be pleasant. I now have longer bolts for the reinstall.

It's raining out, so i'm not gonna work on it right now. Maby if it clears up later i'll do er. I also have plans to drop in tire spats soon.

stevey_frac · 06-23-2009, 10:28 PM

The paint is drying on Air Dam V2!

Some of the improvements over V1 in case someone reads this thread and can learn from my mistakes:

1) It's not as agressive. My original approach extended slightly lower then the lowest body components. It rubbed on anything/everything, and after a week looked horrible. This only extends down 2".

2) 2 Coats of paint! Hopefully it'll stay blacker, longer!

3) Lock washers, and longer bolts then i absolutely needed. I lost a piece of my air dam last time! This time, with lock washers, hopefully they don't vibrate off.