Whats pressure ratio?

[AnotherRedHead]

I am playing with desktop dyno and on blower turbo stuff it asks for presure ratio? What the hell is that? Ive got the boost press input, and the cfm rating and stuff, but cant seem to figure out what that is? It only goes to 10, but if I mess with it any way, it makes a huge difference on my dyno graph? Whats the deal with this shitty junk! I thought it was supposed to be cool! A friend sent it to me, let me know if yall want to use it....

[Ylw 98~~SNAKE~~]

say your total dicharge psi to your intake is 17 psi. The pressure drop through all the plumbing etc is 3 psi. So basically your turbo is putting out 20 psi. lets say the pressure at the inlet of your compressor is -.5psig because it is drawing air into itself. What you want to do is convert that to absolute pressure by doing this


Pout/Pin= (20+14.7 <--standard atm. pressure)
----------------------------------------------- = 2.44
(-.5+14.7)

2.44 is your turbo's compression ratio

heres a good site that explains all of that and more

http://www.gnttype.org/techarea/turbo/turboflow.html