conversion help - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

drift_newbie · 04-09-2003, 06:23 AM

How do I convert cubic feet per minute, (cfm,) to pounds per minute,(lb/min.)?

thanks;

Ben

AKADriver · 04-09-2003, 08:18 AM

That depends what flow you're trying to measure... air, right?

Air density at STP = 1.29 g/L = 0.0805 lb/cf

so 1 cfm = 0.0805 lb/min for air at STP (standard temp and pressure).

At different temperatures and pressures the density will change.

drift_newbie · 04-09-2003, 01:57 PM

Thanks for the info!

You were right on your guess of airflow. Basically, what I'm trying to do is work my way through the caculations in Maximum Boost on sizing a compressor. I've got the charts off of Turbonetics site, and I've done the math from the book, but I couldn't figure out how to convert the flow from cfm, (what the book gives,) and lb/min that is on the Turbonetics charts.

So, would the caculation that you provided work for this? In the book it gives a chart, (Table 3-1 if you have the book,) but that numbers seem to not add up, giving me like 390 lf/min based off of a cfm of 392.13 at 2000 feet of elevation.

I'm dying here! I've been figuring these all day from the numbers I came up with, and every compressor's surge point is lying way to the left of the surge line. Somethings not right!

HELP!!!!!!!!

-ben
*math-challenged, in case you couldn't tell...*

04-09-2003, 06:23 AM	#1
drift_newbie Leaky Injector Join Date: Jan 2003 Location: Midwest Posts: 120 Trader Rating: (0) Feedback Score: 0 reviews	conversion help How do I convert cubic feet per minute, (cfm,) to pounds per minute,(lb/min.)? thanks; Ben __________________ Putting a smart-ass comment here is just setting yourself up to get slammed

04-09-2003, 01:57 PM	#3
drift_newbie Leaky Injector Join Date: Jan 2003 Location: Midwest Posts: 120 Trader Rating: (0) Feedback Score: 0 reviews	Thanks for the info! You were right on your guess of airflow. Basically, what I'm trying to do is work my way through the caculations in Maximum Boost on sizing a compressor. I've got the charts off of Turbonetics site, and I've done the math from the book, but I couldn't figure out how to convert the flow from cfm, (what the book gives,) and lb/min that is on the Turbonetics charts. So, would the caculation that you provided work for this? In the book it gives a chart, (Table 3-1 if you have the book,) but that numbers seem to not add up, giving me like 390 lf/min based off of a cfm of 392.13 at 2000 feet of elevation. I'm dying here! I've been figuring these all day from the numbers I came up with, and every compressor's surge point is lying way to the left of the surge line. Somethings not right! HELP!!!!!!!! -ben math-challenged, in case you couldn't tell... __________________ Putting a smart-ass comment here is just setting yourself up to get slammed

04-09-2003, 08:18 AM	#2
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 43 Posts: 3,517 Trader Rating: (1) Feedback Score: 1 reviews	That depends what flow you're trying to measure... air, right? Air density at STP = 1.29 g/L = 0.0805 lb/cf so 1 cfm = 0.0805 lb/min for air at STP (standard temp and pressure). At different temperatures and pressures the density will change.