This work will present a digital system that allows an on-line experimental determination of the instantaneous torque of either motoring or braking machines.With the procedure developed the machine under test accelerates or decelerates a rigid inertia and all that is required to obtain the instantaneous torque is the instantaneous angular speed signal. An additional external braking or motoring machine, like a dynamometer, is not strictly required, but can add certain value to the testing capabilities. The amount of the total inertia under motion can be determined as part of the actual process with this method.Digital time invariant linear filters are used to process the speed signal using a conventional high level language code running in a microcomputer. The non recursive filters were designed to obtain a short convolution time with a small memory penalty and to handle a noisy speed signal.A personal computer with a commercially available analog to digital conversion card and a graphic display are used to lower the cost of the testing equipment. With this system the performance curves can be displayed on the screen as the test proceeds. The use of a computer increases considerably the possibilities of the method and favors the ease of use.Several methods to compensate the errors due to the torque losses from the machine output up to the inertial mass are presented.Complete simulation of real life steady and transient operation of the machine is possible with this system if an additional braking or motoring device is added to simulate the external load.The computerized system, the instrumentation, and the mechanical facility required for using this technique are combined in a motorcycle roller test bench that is used as a road simulator.