what is the formula to find the area of a circle with a 55 mm diameter????

FED 387 · 07-20-2008, 11:17 PM

OK all you math guys what is it or how do you convert inches to MM--Comp 387

Alan Roehrich · 07-20-2008, 11:36 PM

An inch is 25.4 MM. A millimeter is 0.03937007874".

FED 387 · 07-20-2008, 11:41 PM

Thank you--comp 387

Adger Smith · 07-20-2008, 11:52 PM

Dick,
This is very handy for formulas. I keep it around to help cover my A** when I'm brain dead. Which happens alot!!
http://www.csgnetwork.com/automotiveconverters.html

FED 387 · 07-20-2008, 11:59 PM

Thanx Adger great site---Actually was trying to figure the most aerodynamic hood scoop and the necessary opening to handle some carbs-----Thanx Comp 387

Adger Smith · 07-21-2008, 01:39 AM

According to: Bob Szabo article

One method for ball-parking the size of a hood scoop is to look at the column of air that the hood scoop takes in from the speed of the vehicle. That amount is a function of the engine air demand, the velocity of the vehicle, and the inlet scoop area. The equation for that relationship is:

vehicle velocity = engine air demand / scoop area

Try this:
vehicle MPH = (engine cfm / scoop area in square inches) x (60 x 1/5280) / (1/144)

where:

60 = minutes (m) per hour (H)
1/5280 = miles (M) per foot (f)
1/144 = square feet per square inch
(60 x 1/5280) / (1/144) = 1.64
vehicle MPH = engine CFM x 1.64 / scoop area (square inches)

FED 387 · 07-21-2008, 09:08 AM

Adger by engine CFM are you using the maximum carb flow OR the maximum flow of the heads OR the amount of air the engine will need? Comp 387

FED 387 · 07-21-2008, 09:31 AM

Adger some numbers to use maybe??? 155 MPH ---2 55MM barrels on 1 carb--- heads flow 300 cfm how big (min area) scoop do I need according to your formula--Thanx Comp 387

BoydW · 07-21-2008, 09:13 PM

Comp387
The formula for finding the area of a circle/diameter is: Area= pi times the diameter squared and then divide the whole thing by 4. This will work for either the (SI) metric units or english units. You will want convert your SI units to English or vise vera before making your calculations. If you don't you will have to divide the result, if you are metric units, by (25.4mm/in) squared to get english units or if you are in english units, you will need to divide the result by (0.03937007874 in/mm)squared to get metric units. For a 55mm diameter, the area should be 2375.829mm^2 and 3.683in^2, (^2 is symbolic for squared) Hope this helps, Later, William

07-20-2008, 11:17 PM	#1
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,416 Likes: 522 Liked 330 Times in 178 Posts	what is the formula to find the area of a circle with a 55 mm diameter???? OK all you math guys what is it or how do you convert inches to MM--Comp 387

07-20-2008, 11:36 PM	#2
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,105 Likes: 1,564 Liked 1,789 Times in 408 Posts	Re: what is the formula to find the area of a circle with a 55 mm diameter???? An inch is 25.4 MM. A millimeter is 0.03937007874". __________________ Alan Roehrich 212A G/S

07-20-2008, 11:41 PM	#3
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,416 Likes: 522 Liked 330 Times in 178 Posts	Re: what is the formula to find the area of a circle with a 55 mm diameter???? Thank you--comp 387

07-20-2008, 11:52 PM	#4
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: what is the formula to find the area of a circle with a 55 mm diameter???? Dick, This is very handy for formulas. I keep it around to help cover my A** when I'm brain dead. Which happens alot!! http://www.csgnetwork.com/automotiveconverters.html __________________ Adger Smith (Former SS) Last edited by Adger Smith; 07-20-2008 at 11:53 PM. Reason: sp

07-20-2008, 11:59 PM	#5
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,416 Likes: 522 Liked 330 Times in 178 Posts	Re: what is the formula to find the area of a circle with a 55 mm diameter???? Thanx Adger great site---Actually was trying to figure the most aerodynamic hood scoop and the necessary opening to handle some carbs-----Thanx Comp 387

07-21-2008, 01:39 AM	#6
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: what is the formula to find the area of a circle with a 55 mm diameter???? According to: Bob Szabo article One method for ball-parking the size of a hood scoop is to look at the column of air that the hood scoop takes in from the speed of the vehicle. That amount is a function of the engine air demand, the velocity of the vehicle, and the inlet scoop area. The equation for that relationship is: vehicle velocity = engine air demand / scoop area Try this: vehicle MPH = (engine cfm / scoop area in square inches) x (60 x 1/5280) / (1/144) where: 60 = minutes (m) per hour (H) 1/5280 = miles (M) per foot (f) 1/144 = square feet per square inch (60 x 1/5280) / (1/144) = 1.64 vehicle MPH = engine CFM x 1.64 / scoop area (square inches) __________________ Adger Smith (Former SS) Last edited by Adger Smith; 07-21-2008 at 01:47 AM. Reason: sp

07-21-2008, 09:08 AM	#7
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,416 Likes: 522 Liked 330 Times in 178 Posts	Re: what is the formula to find the area of a circle with a 55 mm diameter???? Adger by engine CFM are you using the maximum carb flow OR the maximum flow of the heads OR the amount of air the engine will need? Comp 387

07-21-2008, 09:31 AM	#8
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,416 Likes: 522 Liked 330 Times in 178 Posts	Re: what is the formula to find the area of a circle with a 55 mm diameter???? Adger some numbers to use maybe??? 155 MPH ---2 55MM barrels on 1 carb--- heads flow 300 cfm how big (min area) scoop do I need according to your formula--Thanx Comp 387

07-21-2008, 09:13 PM	#9
BoydW Junior Member Join Date: Oct 2002 Posts: 4 Likes: 0 Liked 0 Times in 0 Posts	Re: what is the formula to find the area of a circle with a 55 mm diameter???? Comp387 The formula for finding the area of a circle/diameter is: Area= pi times the diameter squared and then divide the whole thing by 4. This will work for either the (SI) metric units or english units. You will want convert your SI units to English or vise vera before making your calculations. If you don't you will have to divide the result, if you are metric units, by (25.4mm/in) squared to get english units or if you are in english units, you will need to divide the result by (0.03937007874 in/mm)squared to get metric units. For a 55mm diameter, the area should be 2375.829mm^2 and 3.683in^2, (^2 is symbolic for squared) Hope this helps, Later, William