The VKI-R4 test rig is a high speed compressor test bench with a closed loop system that can be pressurized from vacuum to 3 bars. This gives the possibility to modify independently the Reynolds number and then to test different operating conditions for an aero-engine (takeoff, cruise,...). The maximum shaft speed is 25 000 RPM. It has recently undergone a deep renovation phase mainly focused on a more efficient cooling system to stabilize the temperature even on high power regimes (500kW). In the frame of the EU project LEMCOTEC, the facility is currently equipped with a single stage HP.