Selecting turbo based on pre-determined boost level?

[gsxrken]

Tippy made an interesting post in Rey's EFI Mistress thread about modern turbos working better or being optimized at higher levels of boost. Rather than take that very cool build thread OT, I thought I'd start a new thread. Efi conversion to the Mistress

Originally Posted by Tippy

Gotcha. Just stating these modern turbos are deliver the goods at higher boost pressures than lower.
Example, our engines using a 60-1 is pretty well matched with say a bar. Move to 1.5 bar, and the 60-1 is out of breath.
Take your Garrett. At 1 bar, it's not really generating a lot of airflow. Turn it to 1.5, and it comes alive.
Modern compressors like higher pressures.

If all other things were equal (comp ratio, displacement, mods) how should one pick a turbo if you knew ahead of time you would run 0.7 or 1.0. or 1.2 lbs of boost? Is this where turbo maps really come into their own, where there is one sweet spot so pick the right one for your desired boost level (not HP number)?

[Tippy]

Yep, maps are everything.

Read Garrett's turbo tech; it explains it all.

Squirrel Performance has a built in calculator you can play with too that's pretty fun.

The turbine side is harder to figure. Compressors are pretty cut and dry. Meaning, balancing response to peak airflow/hp parasitic loss is a little trial and error on the turbine side.