pest007 said:i know how they work i know wat they do but i still have questions.....i wanna know wat the difference is between buying a turbo kit and building a turbo kit form different parts ...and also does hte psi u set depend on how big the turbo is?
i know what CFM are but psi is a bit obscuresoncep said:And Psi vs Cfm are 2 diffrent thing.
Your explanation didn't teach me muchBig Pat said:PSI means Pounds per Square Inch. That is why people say "I got 15 pounds of boost" sometimes. It is an absolute measure, not a comparative one.
However, in the turbo world, boost in PSI is given in relative to atmospheric pressure, just like you said.
And Psi vs Cfm are 2 diffrent thing.
A high flowing head will require less psi for more power as it will accept greater volume.
a small turbo will put out more psi easely but will loose pressure as the volume requirement increase.
200sxBoY said:i know what CFM are but psi is a bit obscure
CFM cubic feet per finute can also be called lbs per minute
but PSI ... per square inch, is that a ratio comparing to atmospheric pressure ?
i mean atmospheric pressure at sea is something like 14.3psi i think, so if your turbo spools up 10 psi that means your pushing 24.3psi (without calculating ari filter restriciton and other stuff) ?
i never really stoped to this , i don't really know how it works but it must be quite simple.mazda2002 said:I would think that 10psi of boost is 10psi over ambiant pressure. (just think how a mechanical boost gauge works)
dead link *td*jfsanterre said:It's not realy for turbo, but read that help me a bit to understand Volumetric efficiency: http:/www.yawpower.com/martech.htlm
so if i put an intake tube with 300mm of diameter, il push like 30 psi but still get the same cfm's ...Faouzi 1.8T said:The boost is the pressure at which the air is compressed.
The CFM is the amount of air going through something (like piping and intake manifold)
A big turbo that spools at 7 psi equals the CFM of a small turbo that spools at 15 psi for example.
For a quick, easy to understand example: Blow in a straw (you might be able to acheive 1 psi) and blow in a towel paper tube (0 psi) but there is alot more air exiting the end in the tube than in the straw.
It's that easy.
Another example, I'm running my K03 sport at 18 psi and i hardly have 210whp and a buddy of mine is runing 20 psi with his gt30R and he got dynoed @ 301whp. Notice the difference!? the actual compression of the air very similar but since he's got about 2 times more air flow (CFM) it ends up producing 100whp more than my set-up. This may sound strange but it's the honnest truth of PHYSICS...
I hope that this helped