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Unread 03-29-2013, 08:15 PM   #37
Got Wood.
Join Date: 01-02-13
Location: La Mirada, CA
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Originally Posted by dwfisk View Post
Here is how my math works, I hope area still = pie-r-squared
diameter 3/4 = 0.75 in
radius = 0.375 in
0.375 x pie = 1.178 sq in
4 of them = 4.71 sq in
diameter = 2 in
radius = 1 x pie = 3.14 blah blah blah
1 exhaust = 3.14 sq in
diameter = 3 in
radius = 1.5 in
1.5 x pie = 4.71 sq in
Have I screwed up somewhere?
I would get my exhaust AT LEAST in balance with intake. Actually, I'm a pretty strong beleiver in a wide open exhaust and control at the intake so I would be tempted to oversize the exhaust and go to 4 in. I dont know squat about UDS cookers, but I see a bunch on here with only 2 or 3 3/4 inch intakes so I'm assuming 4 might be enough.

Oh yeah, in my house, pie-r-round, cobblers-r-square (maybe rectangular).

PS: stopped by my local muffler shop and picked up a 3 ft chunk of 4 inch for $20 for another build we are starting.
Dave, I could be wrong but I thought the formula for area of a circle was radius squared x pie. So in my case I'd have:
.75/2= .375 radius
.375 x .375 = .1406 radius squared
.1406 x 3.14 = .4415 square inches of one 3/4" circle
.4414 x 4 = 1.766 is my total intake.
A 3" exhaust using the above formula would give me a 7.06 sq in exhaust.
I'm going to look for a airflow calculator now to see where I should be at.
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