Ejector-jet apparatus for moving a medium by dragging it with a jet of another (high-pressure) medium moving at high speed; in the process of subsequent mixing, the ejected and ejecting (active) media exchange energy. Ejectors are widely used in test benches for fire tests of taxiways with the aim of creating a vacuum at the exit section of the jet nozzles (to simulate high-altitude condi-tions), noise attenuation, and neutralizing fuel combustion products. Ejectors can also be used in air-rocket engines and as booster pumps. The purpose of this article is to study the jet apparatus characteristics at high pressures at the ejector’s intake (0-0.6 MPa), as well as to develop a new calculation methodology for the rheometer. Studies were conducted on a laboratory stand. The results show that, the maximum value of the ejector efficiency is equal to 35 %, and the injection rate varies from 1-1.19, under these conditions. The new rheometer calculation methodology can reduce the inaccuracy from 20% to 1.8%. © 2021, Univelt Inc. All rights reserved.