The design and implementation of a Computer Controlled System for testing Air Brake Compressors is described. Technical challenges of converting from a manual to a computerized test system are discussed from a practical viewpoint. The accuracy and repeatability of the computer system is compared to the traditional manual system.The system automatically controls compressor operation during a variety of test routines used to approximate actual operating conditions. This requires the computer system control compressor operating parameters such as the rotational speed of the crankshaft and the discharge air pressure. The techniques used to interface the computer system with a variety of electro-mechanical and electro-pneumatic control devices are described.To evaluate compressor performance the system monitors and records many operational characteristics such as the flow rate and temperature of air delivered by the compressor, instantaneous crankshaft torque, and horsepower requirements. The system can analyze the collected data and present it in either tabular or graphical format. Calculation of compressor performance indices, for example volumetric efficiency, can be automatically preformed.