Mayf, that's how it's determined in a parallel-wall or a scroll type
diffuser, I'm not sure how you do the calc's in a vane type.
There's a very good book with a lot of the information you need called
"Turbochargers". It's produced by HP Books and written by Hugh MacInnes, the
father
of the TRW later Rayjay turbo.
At the risk of ruffling your feathers why are you even looking at compressor
trims? A .60 or a .70 is not going to make a hill of beans to what you trying
to do. Look at the compressor map, pick a turbo the will move enough air to
make the power you need or want (seems I said this a couple years ago when you
started this project) and bolt them on.
Just remember in my opinion the turbine side will because you more trouble
than the compressor side by a factor of 4 to 1. If you have too much back
pressure in the system it can affect everything else from the durability of the
exhaust to the fuel injection. I monitor the turbine inlet temp and pressure.
If
your system has more exhaust pressure than inlet pressure your ability to
continue to make more power falls off dramatically in long distance type
running.
Good Luck and have Fun.
Mike
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