Definition of "CFM"

85_SS_302_Coupe

it sucks (I know) to be on the receiving end
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Nov 11, 2003
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It dawned on me the other day that i don't know exactly what "cfm" stands for, so now i feel completely noob :bang: I've looked around and all i can find is some serious physics type definitions that i barely understand, mainly "contraint force mixing"....is this the right definition or am i going off on another path?
 
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85_SS_302_Coupe said:
Yea that's what i had guessed but then i got all this constraint force mixing crap and it totally threw me off. And then i read that cubic feet per minute is an assumption.... :shrug:

I think it would be an assumption. Using a carburator as an example, it assumes that a 600cfm carb would draw 600 cubic feet per min of air is left at wide open throttle for 1 minute but there are too many factors that can affect the carb to include air density. Now I may be totally wrong on that statement but if you read it, it sure does sound smart!! :D
 
Yeah it's cubic feet per minute which is a standard measurement of airflow that indicates how many cubic feet of air pass by a stationary point in one minute.

According to a definition "1 CFM equals approximately 2 liters per second"...but wouldn't that be 1200 liters of air in a second with a cfm of 600 (carbed example)...seems a bit high to me:shrug:
 
and if talking about fan draw, note that the procedure used in measuring makes a world of difference (a better flowing fan can show poorer relative flow numbers than an inferior fan simply from different testing protocol).
 
5spd GT said:
Yeah it's cubic feet per minute which is a standard measurement of airflow that indicates how many cubic feet of air pass by a stationary point in one minute.

According to a definition "1 CFM equals approximately 2 liters per second"...but wouldn't that be 1200 liters of air in a second with a cfm of 600 (carbed example)...seems a bit high to me:shrug:
that would be 1200 liters per minute not second...
 
Wow guys, that's some pretty poor dimensional analysis. :rolleyes:


1 [ft^3] (cubic foot) = 28.317 [liters]

1 [ft^3/min] (cubic feet per minute) = 28.317 [liters/min] (just divided both sides by the unit 'minutes')

Therefore, 600 [ft^3/min] * 28.317 [liters/ft^3] = 16,990.2 [liters/min]

16,990.2 [liters/min] * 1/60 [min/sec] = 283.17 [liters/sec]

Make sense?
 
mackey said:
How does 1cfm equal 2 liters per second. Please link me to the source you got that from. That is wayyyy off.

It was off some link when I did a quick search for the definition...later on down it talked about air conditioning units though...so that could be the "difference"...

illwood - Nice copy and paste :)