Abstract The structure of newly designed turbo rotary Pars turbine shows similarities with the structure of commercially available vane compressors. The vane is embedded within the turbine mainframe whereas the other end is hinged to the rotor liner. Friction loads and pressure leaks occur in the vane side surface during the operation of the turbine. Therefore, design studies that reduce the friction losses and pressure leaks of the vane which improves turbine performance. In this study, the effects of friction and pressure leakages on the performance of the turbine have been investigated. Vane thickness size has been changed. Three different sizes (thick, standard and thin vanes) have been experimentally investigated. The experiments are also repeated by reducing the vane weights without making any changes on the outer geometry of the thick and standard vane. As a result of the experiments, 75% more power of the turbine has been obtained for the thin vane.