wait a sec...

bigger turbo bigger volume of air?

i'm going to actually disagree (and yes i DID read that big turbo essay from stu and it was my orignal Q about this on RSBB that sparked it all off )

you have a certain rea to pressurise right? you got your combustion chamber, inlet ports on the head, inlet manifold+plenum, boost hoses, intercooler etc.

now whe you pressurise these to 2bar absolute (ie 1bar bost) then lets say for example you have 1 million air particles (imagine theyre FOOKIN big particles)

why would it matter which turbo is used to pressurise this air?

1 million particles @ 2bar is 1 million particles at 2bar nomatter what way you look at it.

surely?

or am i missing something obvious?

i can see how a larger turbo has the potential to flow more volume of air but i cant see how a T34 cossie running 20psi can physically have more air running thru the inlet tract (which is what you are measuring with your boost gauge) than a T4 cossie running 20psi. i CAN however see how they create more power for the same volume of air tho...