Turbo Size

[Inane]

The short answer is, that no matter what size turbo you are running, if it is
limited to 15 psi, you make the same power.

If you have 15 psi, then you have 15 psi. It doesn't matter if it comes
from the meanest mother of all race turbos, an electric fan, a steam
powered compressor or a choir of angels farting in unison... all you
have is 15 psi

So without taking heat into account, you think all turbos at 15psi would
flow the same volume of air in a given space of time at the same rpm?

If this is true, then it contradicts what people earlier said about larger
turbos flowing more air at the same psi.
If Jondee86 is correct in his same psi same flow arguement, does that
mean the only benefit a larger turbo has at the same psi, would be heat
efficiency? (assuming all other variables are constant, ie: piping size,
port size, intake manifold etc)???

As already stated, pressure is not a measure of volume.
As a real example, by car has enough fuel stock to cope with 14psi from my T25. When I put my GT28R on tho, it will only have enough fuel for about 8psi, but it will still make more power on 8psi on the GT28R because there is still more airflow and less heat.

So if what I understand of Jondee86's arguement is correct, Rollux is
making more power and using more fuel , not because of increased flow
of air volume, but purely on heat efficiencies of the larger turbo?

its going to depend on where you are taking the measurements of boost from.

what jondee is trying to say (i think) is that, no matter what your turbo is doing, whether its spinning at 1 rpm or 1,000,000 rpm, you only have a set (finite)amount of space for it to push pressure to.

[jondee86]

EXACTLY !!!!!

In this question the parameters are fixed !! The orifice size (call it what
you like) is set by the physical dimensions of the opening through which
the air/fuel mixture must flow. And at some rpm (fixed but not stated)
and at a pressure of 15 psi, a certain flow will occur.

Leaving aside variations due to temperature, the power developed by
the engine under these fixed conditions will be the same no matter what
type of air pump you use.

Do not confuse this simple example with the much more complex real
life question of matching turbo size to engine size. Obviously large turbos
will flow more air and develop higher pressures than small ones, and
efficiency, temperature, rpm and other variables will need to be
considered.

A small turbo will never make high boost on a large engine. Why ?
Because the pressure developed is governed by the restriction the turbo
must work against.... it simply can't flow enough air.

Cheers...... jondee86

[10k 20v]

and to add, when you fit a larger exhaust housing you remove some of the resriction so you have to flow more air to get 15psi, and add the cooler air temps you engine may make more power for the same boost presure.