Abstract: A method and apparatus for providing a signal representative of the output torque of an internal combustion engine utilizes a correlation of average engine speed and variations in instantaneous sub-cyclic engine speed. The variations in instantaneous sub-cyclic engine speed involves a measure of the difference in those instantaneous speeds occuring at a pair of crank angles in each firing interval of an engine cycle, each crank angle of the pair being separated from the other by substantially one-half of the firing interval. The pair of crank angles in each firing interval across which the instantaneous speed difference is measured preferably are the middle of the interval and either the beginning or the end of the interval. The measured valves of instantaneous engine speed may be adjusted to remove the effects of transient changes not related to the individual cylinder firings.

Abstract: Methods for determining rate of fuel flow to a combustion engine is disclosed. The fuel flow rate determination is made by measuring a pertubation in air-to-fuel-flow ratio to the engine, or in the volumetric concentration of a gaseous test species in the exhaust, after adding a known amount of a test substance to the air flow intake to the engine, or to the exhaust from the engine, respectively. The desired fuel flow rate is calculated from the measured parameters.