Suggested Aerodynamic Mods for a Cobalt - Page 4 - Fuel Economy, Hypermiling, EcoModding News and Forum

stevey_frac · 06-02-2009, 01:20 PM

First trip report with the grill block in place.

Temps were slightly higher then normal, but the thermostat is still not open all the way, so i believe i'm fine. The fan didn't come on once, including the brief periods of times when the A/C was on. So I fairly confident i haven't gone too far.

It's hard to gauge improvement without controlled tests, but i'd estimate about a 2% improvement in aero, going by feel and how i know my car.

-Steve

NeilBlanchard · 06-02-2009, 01:34 PM

Hi Steve,

On my xA, I found I had better cooling with the upper grill block complete. And you'll want to experiment with a cover on the "chin" opening, which will force the air to flow through the radiator, and not vent out the opening -- but this might end being like your belly pan. You have to balance the grill opening size and the the amount of air you let out.

But in the end, I think anything you do to restrict the air flow through the engine compartment helps your belly pan work better, and any air that you can deflect up and over the hood/car helps, too.

stevey_frac · 06-02-2009, 01:58 PM

I like your thinking Neil. A chin guard might help force more air over the radiator. I'll have to look into that. Once I get some more Coroplast!

stevey_frac · 06-03-2009, 09:38 AM

Ok, so now... What should i Do next? Chin guard, or diffuser? I kind think the back bumper might be acting as a parachute. It's got an edge that i would bet is really catching the air that goes underneath. But the bottom of the engine compartment is wide open to...

-Steve

NeilBlanchard · 06-03-2009, 10:39 AM

Hi Steve,

I'd try making you hubcaps smooth. Or, I'd cover the opening between the front fascia nd the radiator; combined with a partial lower grill block.

aerohead · 06-06-2009, 04:26 PM

Quote:

Originally Posted by stevey_frac

Ok, so now... What should i Do next? Chin guard, or diffuser? I kind think the back bumper might be acting as a parachute. It's got an edge that i would bet is really catching the air that goes underneath. But the bottom of the engine compartment is wide open to...

-Steve

I would suspect that the lower edge of the bumper is already hiding in the wake of the underbody with air just barely kissing its underside.GM's too smart to overlook these kinds of details now.I'll look underneath a Cobalt in the morning cool when I have the opportunity.The Monte Carlo is very clean and the Corvette is a benchmark now for underbellies.

stevey_frac · 06-06-2009, 04:34 PM

I just tried to take a picture of my bumper to show you what i mean, however, without context, the picture just just a bunch of crap. Truthfully, I'm kinda disappointed. I don't see any easy way forward to make significant gains. The underbelly of the cobalt could use improvement yes, but it's already pretty good. The wheel wells don't contribute to massive amounts of drag, moonies are expensive ($150 for real moonies), and I think that any attempt I make at wheel skirts are gonna come off hokey. At the moment the only thing i have planned is a switch to synthetic oil, at a slightly thinner viscosity. I might get the moonies if I get some extra work.

Big Dave · 06-06-2009, 05:20 PM

stevey frac:

Sounds like you are hot on the trail of improved aerodynamics.

Have you looked into swapping in the numerically lower gears used in the Cobalt XFE? Numerically lower gearing will help you reap the benefits of better aero.

stevey_frac · 06-06-2009, 05:52 PM

Quote:

Originally Posted by Big Dave

stevey frac:

Sounds like you are hot on the trail of improved aerodynamics.

Have you looked into swapping in the numerically lower gears used in the Cobalt XFE? Numerically lower gearing will help you reap the benefits of better aero.

The cheapest way to do this is to swap in a whole used transmission. This would I believe through off the speedo and odometer, and requires dropping the engine. It would end up costing over $1000, and i can't justify it. Should i need to replace my transmission, i would try to do so then.

aerohead · 06-06-2009, 05:59 PM

Quote:

Originally Posted by stevey_frac

I just tried to take a picture of my bumper to show you what i mean, however, without context, the picture just just a bunch of crap. Truthfully, I'm kinda disappointed. I don't see any easy way forward to make significant gains. The underbelly of the cobalt could use improvement yes, but it's already pretty good. The wheel wells don't contribute to massive amounts of drag, moonies are expensive ($150 for real moonies), and I think that any attempt I make at wheel skirts are gonna come off hokey. At the moment the only thing i have planned is a switch to synthetic oil, at a slightly thinner viscosity. I might get the moonies if I get some extra work.

41.73 mpg is nothing to sneeze at! I've got to go(stores closing) but I'll look at Cobalts.