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01-16-2002, 04:24 PM

OK the reason it sounds wrong is because it is

Let me see if i can help you.

To get the NA-CFM which is just a measure of the volume of air that your engine can consume naturally aspirated. Since you have a B16 im going to assume you rev to 7500 (i dont know what the redline is ill just pick a # as an example). So this is what your formula will look like.

97.632 X 7500 X .5 X .85 / 1728

Notice i used 7500 as the rpm being that is the engines maximum rpm. Also .5 because it is a 4 stroke engine and i guessed .85 as the VE which is reasonable.

When you do the equation you come up with 180.09

That 180.09 is how many cfm your motor consumed NA.

now for the next part all it is basically doing is calcualting a pressure ratio. We will make this easy and say in boosting 14.7 psi (AKA 1 bar)

so (14.7 + 14.7) / 14.7 = 2

Basically all that means is in pushing 2 times the atmospheric pressure into the engine so theoretically the engine should double in CFM. Lets find out,this is where there is an extra step. If its not listed ill fix the sticky

2 X 180.09 = 360.18

That 360.18 is the amount of CFM the engine consumes while exposed to 14.7 psi of boost. This # will be useful when looking at compressor maps.

For a list of compresor maps there are a few listed at
www.turboneticsinc.com

If you want to know any other formulas for engines just let me know. I have one for everything from calculating piston speeds to figuing out compresssion ratios.

01-16-2002, 04:24 PM	#2
Boosted3g Posts: n/a	OK the reason it sounds wrong is because it is Let me see if i can help you. To get the NA-CFM which is just a measure of the volume of air that your engine can consume naturally aspirated. Since you have a B16 im going to assume you rev to 7500 (i dont know what the redline is ill just pick a # as an example). So this is what your formula will look like. 97.632 X 7500 X .5 X .85 / 1728 Notice i used 7500 as the rpm being that is the engines maximum rpm. Also .5 because it is a 4 stroke engine and i guessed .85 as the VE which is reasonable. When you do the equation you come up with 180.09 That 180.09 is how many cfm your motor consumed NA. now for the next part all it is basically doing is calcualting a pressure ratio. We will make this easy and say in boosting 14.7 psi (AKA 1 bar) so (14.7 + 14.7) / 14.7 = 2 Basically all that means is in pushing 2 times the atmospheric pressure into the engine so theoretically the engine should double in CFM. Lets find out,this is where there is an extra step. If its not listed ill fix the sticky 2 X 180.09 = 360.18 That 360.18 is the amount of CFM the engine consumes while exposed to 14.7 psi of boost. This # will be useful when looking at compressor maps. For a list of compresor maps there are a few listed at www.turboneticsinc.com If you want to know any other formulas for engines just let me know. I have one for everything from calculating piston speeds to figuing out compresssion ratios.