rdssk8rcs1

Looking for some insight on the differences and comparisons on these and how they effect power. Either inside this forum or links to other articles. Thanks in advance

tannerLSt

http://forums.evolutionm.net/a....html

rdssk8rcs1

Thank you. I will read that later on. Sifted through it real quick and it looks like exactly what i was looking for

rdssk8rcs1

read through that. It ended up being more of an argument rather that facts. Does anyone have any other light to shine on this?

base-op.1320

From what I have learned - x psi on a small turbo is the same as x psi on a larger turbo, a smaller hot side will spool faster but restrict overall power while a larger hot side will lag but make more overall power - psi is just the amount of air being backed up above what your engine will naturally use but cfm is the maximum amount of air a turbo will flow

rdssk8rcs1

Thats some good information. I was hoping for a little more indepth

base-op.1320

Your question is kind of vague, could you explain what you are trying to figure out a little better, but to try to answer your original question a little better from what I know - anybody feel free to correct me if you think I am wrong. Psi and cfm are different - your engine naturally aspirated flows a certain cfm with 14.7 psi of atmospheric pressure entering it, any air that a turbo supplys above that cfm is then a pressure (psi) being backed up into the intake and chargepipe which in turn begins to force more air into the cylinders. In theory if you run 14.7 psi of boost you would be doubling the normal cfm of the engine. If you took a stock engine that naturally flowed say 300cfm and put a turbo kit on it with 14.7 psi it should flow around 600cfm and would make the appropriate hp for that cfm. Now take a very efficient engine with headwork, cams, intake, tb that may flow around 400cfm put the same turbo kit on it and it might only take 10psi to flow 600 cfm making around the same hp (maybe more because of cooler charge temp), but at 14.7psi it would flow 800 cfm (as long as the turbo can flow 800cfm efficiently) I hope all of this helps and let me know if you still aren't getting your question answered.

sneakysneaky

if you want in depth differences between airflow and pressuare ask an aerodynamical engineer. but play with a water hose, at a high pressuare you lose volume. water and air arent the same mediums becuase water doesnt compress but same basic concept. when ppl say your turbo isnt efficeint at whatever pressuare island its because its chocking itself to death and not flowing air efficeintly.

blinx9900

PSI is a unit of measure for PRESSURE
CFM is a unit of measure for VOLUME

that is the main difference.

rdssk8rcs1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blinx9900 &raquo;</TD></TR><TR><TD CLASS="quote">PSI is a unit of measure for PRESSURE
CFM is a unit of measure for VOLUME

that is the main difference.</TD></TR></TABLE>

I understand that my question is what is there relation to the power output of the engine

Schister66

The measurement that determines power output is the Lb/min of the turbo regardless of the pressure ratio needed. Take a little time to learn how to read compressor maps and you'll have a better overall grasp of the diifference between psi and cfm.

blinx9900

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rdssk8rcs1 &raquo;</TD></TR><TR><TD CLASS="quote">

I understand that my question is what is there relation to the power output of the engine</TD></TR></TABLE>

um wow, really? i thought if you understood that you can understand why both are equally important. thats a pretty vauge question that could have a very long answer but i will just leave it at this:

there not independant of each other or other factors like heat/density. fuel systems work the same way, one part of it is pressure, the other part is volume.

Snafubmx234

CFM (Cubic foot per minute) is a volumetric flow rate.

Pressure is a property that can be used to determine the state of a substance.

There's a lot more too it, but the more mass you can move through the system in a unit of time is better than having the properties of that mass change due to an increase in pressure.

rdssk8rcs1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blinx9900 &raquo;</TD></TR><TR><TD CLASS="quote">

um wow, really? i thought if you understood that you can understand why both are equally important. thats a pretty vauge question that could have a very long answer but i will just leave it at this:

there not independant of each other or other factors like heat/density. fuel systems work the same way, one part of it is pressure, the other part is volume.</TD></TR></TABLE>

um wow, really? Thanks for the lack of infromation and help with your posts. Please take your own word and "leave it at this." Thank you for wasting 2 posts in this thread.

blinx9900

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rdssk8rcs1 &raquo;</TD></TR><TR><TD CLASS="quote">

um wow, really? Thanks for the lack of infromation and help with your posts. Please take your own word and "leave it at this." Thank you for wasting 2 posts in this thread.</TD></TR></TABLE>

I'm sorry i don't mean to offend you I simply lack the ability to explain it in such basic terms for you to understand.

rdssk8rcs1

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blinx9900 &raquo;</TD></TR><TR><TD CLASS="quote">

I'm sorry i don't mean to offend you I simply lack the ability to explain it in such basic terms for you to understand.</TD></TR></TABLE>

Im sorry if its so hard for you try to find a way to explain it. Sounds like this is more an issue of you lacking complete understanding of the topic in the first place. Any topic that is completely understand by someone is easily explained and taught to anyone else, but someone like that that skips step one and tries to go directly to step two finds themself "having a hard time explaining it."

Thank you for your input regardless

NJIN BUILDR

I think you already know the answer.In basic terms it's cylinder fill that matters.You already know what the terms mean.As cfm goes up,psi (*backpressure in the intake*)goes down.I have heard people complain because their engine won't make as much boost (psi) after a cylinder head upgrade,in spite of the fact it made a lot more HP.