Turbocharger Compressor Efficiency is the ability to produce the lowest possible compressed air temperature at a specific turbine speed.
When air is compressed heat is generated. Compressor efficiency range is the compressor speed range where the air temperature can be kept to a minimum. Highest possible efficiency of compressors is about 80%.
A higher compressor efficiency equals lower outlet air temperatures and the more power produced. Cooler air is more dense and oxygen saturated. The more oxygen available allows more fuel to be burnt which produces more power.