Frontal Area calculations - GMC Sierra 59.9sf?

[joggerfogger]

Did I do this right? 60 square feet?

I used GIMP and a picture of my truck from the front and got 9,980,928 pixels.
The very tip of my mirror to mirror is exactly 100 inches or 8.33 feet, and GIMP says 3468 pixels.
So the ratio of ft^2 / pixels = .000006 which gives me 59.886sf.?

So my Allison 1000 Transmission manual says 6 times "Coasting in neutral can cause severe transmission damage." So I'm not really going to do any coast down tests which kind of sucks. I'll have to do everything just driving.

[Bill in Houston]

59 seems too high. shes 8 feet wide and 6.5 feet tall, ballpark. So you should be getting a MAX of 52 sq ft. take away underbody clearance, and tapering, and you oughta be in the mid to low 40s. right?

[skyking]

My Dodge is 34.49 per Dodge.
Your truck cab is only 6.4~6.5 wide.

[joggerfogger]

Ok, got her figured out. I had the pixel count for the whole image not just the area of the truck. It's 6,305,730 not 9,980,928. So 37.83 ft^2

I have to fold in the mirrors frequently to park at the office. 8'4" from tip to tip. That was the easiest reference point for me to measure (with the windows down)

I gave a little effort to try and find the frontal area online, but failed. I think I need to take the picture further back to get more accurate numbers, but since I can't do any coast down testing it's a moot point anyway.

The only thing I could really do to reduce the frontal area is to remove the gigantic mirrors, and that makes my frontal area 36ft^2 (35.988)

-Kevin

[Joenavy85]

you figured it based on the size of square tube the truck will fit into, i would say the high 30's max

[aerohead]

Some car magazines publish factory supplied Cds and frontal area data for SUVs which are based on the truck chassis.
If you calculate the percentage of gross area reflected in these frontal areas,you might use this to calculate an approximation based on the Sierras gross area.
And I believe that Photo Shop has a tool which can be used to ascertain the area of an image when the scale is known." I'll leave that one to the computer gurus.
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One thing to mention.In official reporting to the EPA,for certification purposes,the frontal area of mirrors cannot be included for the vehicle and its drag will reflect the presence of the mirrors,however its Cd will be reported for the arbitrarily lower reported frontal area,suggesting that the vehicle is 'dirtier' than it actually is.