Metro aerodynamics

[MetroMPG]

I had the car rust-treated today, so I removed the rear wheel skirts.

[JanGeo]

Hey I just read a post in ScionLife that the drag coefficient of my xB is 0.35

[Peakster]

It's been really gross and mucky outside, so washing my Metro would be dumb since it would just get dirty 10 minutes later. Now that my Metro is caked with road grime this is what she looks like:

Attachment 82

I would think that the clean parts of the car are where the air is going smoothly over the vehicle, but look at all that turbulent air coming from the front wheel arch! Also note how much dirt accumulation occurs on the rear of the car:

Attachment 83

Winter should be a perfect time to test out some Aero mods!

[MetroMPG]

I read somewhere that some aerodynamicists sometimes use dust in the wind tunnel for exactly the same reason - where it accumulates on the car shows areas of low pressure better.

[MetroMPG]

Also, don't kick off the "snuds" (snow & mud) that accumulate behind your tires. Once they're built up, they effectively "boat tail" the air flowing past the wheels and help streamline it.

[Silveredwings]

Originally Posted by MetroMPG

Also, don't kick off the "snuds" (snow & mud) that accumulate behind your tires. Once they're built up, they effectively "boat tail" the air flowing past the wheels and help streamline it.

Oh, I thought those were boogers.

[The Toecutter]

Hey I just read a post in ScionLife that the drag coefficient of my xB is 0.35

If I would have known that you were unaware of this number, I'd have told you!

I found that figure after seeing the AC Propulsion Ebox, wanting to see whether their claims for range and efficiency appeared reasonable, and then doing a search and plugging the numbers into the drag equations we all know about.

[Peakster]

Thinking of doing some aero modifications at some point with my Geo. (even if it's just a one-time thing). Just a few images to bounce around on this site:
Attachment 112
What the air is probably currently doing:
Attachment 113
Attachment 109
Attachment 111
And of course if I was really ambitious:
Attachment 116
Should the rear end taper be the same height as the front point to leave the air least-disturbed when leaving the car?

[CoyoteX]

Find a 93 flat bumper. I tested them and they are better. I don't have any real mileage numbers but from doing a pretty thorough coasting test I can say they are better for the front end than the curved bumper.

[Peakster]

Originally Posted by Coyote X

Find a 93 flat bumper. I tested them and they are better. I don't have any real mileage numbers but from doing a pretty thorough coasting test I can say they are better for the front end than the curved bumper.

I would've thought that a flatter front bumper would be better. The downward angle of my current bumper seems like it rams a lot of air under the car. This is also why my '85 Fiero had a Cd of 0.37 compared to the SE version having a Cd of 0.35:

Non aero nose (my '85 SC Fiero) Cd: 0.37:
Attachment 114
Aero nose ('86 SE Fiero) Cd: 0.35:
Attachment 115

It seems as a rule of thumb that air should flow around the sides or top of the car, not under it. The only problem is that I'm sure the '93 bumpers are not interchangeable with my '97. I would have to fabricate the flat bumper myself.