So with the vnt style of turbo, how do you size one for your application? If the internals are variable and change to meet load conditions, this changes everything, does'nt it?
No, the variable part is on the exhaust, so it just changes how the turbo spools. The map is for the compressor which will pump x amount of air at y psi pressure when turning z rpm. You would size it like any other turbo. But that is also where vane control comes in, to make sure you stay within the safe area as I believe a VNT is easier to put in the surge zone since it spools faster.