Is it better to run a ProCharger towards the bottom or top of its range?

[Gannet]

Let's assume you want about 1400 cfm out of a Procharger. A D-1SC-1 will do that right about at redline. Or an F-1A will do it loafing with the largest blower pullies.

Which will result in the least charge heating?

Which will have the lesser drive loss?

[PowerLabs]

Neither. You have to run any centrifugal compressor in the middle of its efficiency "island" if you want minimal charge heating and parasitic drag per power generated. Here is an example from a Vortech:



You will see that at the peak of its RPM range the efficiency plummets, but it is also very low if you try to run a lot of boost early on, or very late in the RPM range, or a lot of boost in general...