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CMac455
11-28-2005, 09:06 PM
I was wondering if anybody knew how to calculate cylinder pressure with a certain number of boost at a given cfm?

Is there a way to determine how much cylinder pressure it takes to make 600lbstq on a 232cu motor?
Monty Mikho
11-28-2005, 09:23 PM
Not sure what you mean by a given CFM.. Maybe this is what you are looking for..

http://www.rbracing-rsr.com/compression.htm
CMac455
11-28-2005, 10:32 PM
PSI and CFM are two different things. You can have the same boost on any turbo/supercharger, but the CFM is going to be different. In order for that to be accurate, Volumetric Efficiency in terms of CFM would have to be supplied into the equation.

For example, 20psi on a eaton M90 supercharger is around 600cfm and 20 psi on a 2.2 kenne belle twin screw blower is about 1500cfm at 20psi. The change in volumetric efficiency changes dramatically between those two blowers, therefore, the cylinder pressure would be lower for the M90 than the 2.2 kenne belle blower's cylinder pressure is.....

Thank you for the reply. :D
Monty Mikho
11-28-2005, 11:59 PM
Sorry I was thinking about a fuel injected turbo.. :oops: Not sure about blowers..
Six_Shooter
11-30-2005, 06:09 PM
PSI and CFM are two different things. You can have the same boost on any turbo/supercharger, but the CFM is going to be different. In order for that to be accurate, Volumetric Efficiency in terms of CFM would have to be supplied into the equation.

For example, 20psi on a eaton M90 supercharger is around 600cfm and 20 psi on a 2.2 kenne belle twin screw blower is about 1500cfm at 20psi. The change in volumetric efficiency changes dramatically between those two blowers, therefore, the cylinder pressure would be lower for the M90 than the 2.2 kenne belle blower's cylinder pressure is.....

Thank you for the reply. :D

I don't agree with that at all.

Given the same engine, the same CFM and should be required to reach the same PSIG, since PSIG is just a measurment of restriction AFTER the compressor.

On two different engines I would agree with you, since the intake tracts could be very different.