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The flywheel speed is recorded during snap acceleration, while operating the engine without external load and at fully open throttle. A non-contacting magnetic sensor at the engine flywheel detects the instantaneous speed. A digital circuit, which includes a microprocessor, samples and processes the speed data. The speed increment observed over a fixed number of engine cycles is a measure of the engine torque. Since the instantaneous flywheel speed exhibits significant variations, the speed increment is determined on the basis of a linear regression analysis of the speed waveform. The approach was verified experimentally on eight-cylinder Diesel engines. The results from the snap acceleration analysis were found to be consistent with dynamometer measurements within mean relative error margins below four percent.

Many internal combustion engines are equipped with a vibration damper attached to the front. Excessive thermal loads on the viscous damping element occasionally lead to damper failure, which in turn causes excessive torsional oscillation amplitudes in the crankshaft, and subsequent damage to the engine if the damper failure is not recognized immediately. Two non-contacting magnetic sensors at the engine front and flywheel detect the speed at both locations, and the torsional crankshaft strain. A digital circuit, which includes a microprocessor, samples and processes the raw engine speed speed data. The transducer concept provides for stable operation independent of motor speed and varying ambient temperatures. Experimental data were recorded on an eight-cylinder Diesel engine with and without damper. The measurements, made under steady state operating conditions, show that the speed oscillation amplitudes at the engine front more than double when the damper fails.