terminology and turbo questions

[auditude at neta.com]

JShadzi at aol.com wrote:
>
> << Also,  the psi rating of a turbo....
>  Is this the pressure on the turbo outlet, pushing into
>  the intake?>>
>
> Well, turbos are not rated for psi per se, but typically the actual
> psi output is measured in the intake manifold where it counts.
>
> << Or, is this the pressure of exhaust acting on the
>  turbo spooling fins?  >>
>
> No, that pressure is typically not measured, as what is really
> important is in the intake manifold.

Would it be a correct statement to say that "clipping" mods done
to the exhaust turbine fins results in better performance, due to
less backpressure of the exhaust getting out of the motor?  At the
expensive of boost onset rpm (is that different from "boost lag",
which is said to be different in Max Boost)?

At some point, the turbo can be too small, and be a restriction to
the output of the exhaust, right?

I realize this is a different topic than where the thread was, but it's
a factor too, isn't it?

Is the backpressure created by the turbo a factor in its efficiency
for a certain pressure?  I know that clipping changes the a/r, and
that it makes it "act" like a larger turbo, but is this simply due to
the decreased backpressure?  Or, does it have more to do with the
new shape of the fins and the new angle at which the exhaust
gases hit them?

Thanks,

Ken