Monitoring cylinder performance of an engine by measuring output torque from the crankshaft

A method of monitoring the cylinder performance in an internal combustion engine comprises measuring the output torque from the crankshaft of the engine at intervals during the engine cycle, and comparing readings for indications of changes in performance of the engine. Readings may be averaged over an integer number of engine cycles to provide an average torque output for the engine, or the torque at a particular point during or over a particular part of the engine cycle may be measured and averaged over a number of cycles to provide an average torque output for a particular cylinder of the engine. Torque characteristics measured may include peak torque, instantaneous torque versus angle, and average torque during the firing stroke; and these may be analysed to find the firing point and torque generating period of each cylinder. The sampling interval may be 0.8 to 8 KHz and measurements may be taken by a surface acoustic wave (SAW) sensor attached to an engine flexplate.