compressor rotor -- impeller, may be thought of as an air pump.
Nine times out of ten tho, a noisy pump is caused by an obstruction colliding with the rotating impeller.
trimming the impeller reduces power consumption by 2.5 kW (14% ), saving £ 2190 a year.
This is to protect the impeller from large solids, algae or fish waste, and to stop the fountain head blocking up.
Installed a K&N Air filter, replaced impeller on Charge Cooler pump, Installed BOV, Ordered Upgraded ECU Chip.