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# CFM vs PSI Q's

Discussion in 'Forced Induction' started by Domi31, Nov 7, 2007.

1. ### Domi31Member

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Ok tried do some searching on the net but, it lead to a lot of threads where people are just arguing. (that and cfm and psi do not work on most sites searches engines)

Just looking for a clear understanding on why a bigger turbo vs a smaller turbo at the same given PSI will yeld out diffrent CFMs? And How does this effect the power being made.

Why do we always here about psi, more than CFMs. Can someone point me in the right direction.

If a boost guage measures the pressure in a charge pipe at say 7psi, why would it matter on the size of turbo? It seems like, in the same size of piping, 7 pounds is 7 pounds regardless of what turbo is is coming from.
I know that it does matter on the size, I just want to know why?

Thanks for any info,
i guess i just felt like learning something

2. ### pissedoffsolRETIRED

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cfm = volume of air
psi = pressure of air

"MORE" air being "PUSHED" in = more power.

a larger turbo pushes MORE air per psi than smaller ones (in theory, and there are some exceptions)

ultimately, its the extra volume of AIR in the chamber that gets added with gas that combusts. the pressure of said air doesn't combust.

7 psi IS 7 psi, regardless of the turbo, but within those 7 pounds, the volume of air going in can be quite different.

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