Abstract: A method for determining the rotational moment of inertia of an engine, crising the steps of carrying out engine deceleration tests, first with the engine unloaded and later with the engine sufficiently loaded to provide a recordable difference in deceleration rate (or elapsed time). Moment of inertia is determined as the numerical value of the added load divided by the difference in deceleration rates, before and after the load is applied.

Abstract: The full-power condition of an internal combustion diesel engine is tested by an acceleration burst test in which the engine initially operated at idle speed is suddenly given full throttle and caused to accelerate to a maximum governed speed. A tachometer means coupled to the engine produces one electrical pulse per engine cycle. The time taken in going between a predetermined low speed and a predetermined high speed is accurately determined, despite irregularities in the engine, by adding a portion determined by interpolation in the time period between pulses at the low speed, and a portion determined by interpolation in the time period between pulses at the high speed, to the intermediate time periods.

Abstract: An apparatus for, and method of, detecting the uneven operation of the individual cylinders in an internal combustion engine, and for diagnosing the cause thereof. The engine is operated at any convenient idle speed. Power cycle time periods between successive ignition times are measured, the deceleration rates between successive time periods are then computed, and finally the average deceleration rates for the respective cylinders are computed. Misfires occurring randomly in cylinders are detected when individual deceleration rates exceed the average deceleration rate for the corresponding cylinder by a predetermined limit amount. Repeated malfunctioning in an individual cylinder is detected when the average deceleration rate for the weakest cylinder exceeds that for the strongest cylinder by a predetermined limit amount.

Abstract: Apparatus for and method of measuring the ignition timing of an internal combustion engine while cranking the engine with the starter motor, and with the ignition inhibited. Starter motor current fluctuations are examined to determine the times of current peaks due to compression in individual cylinders. Means coupled to the ignition circuit determines the times of points openings. A time difference signal representing the lead or lag of the ignition relative to the starter current peaks is generated. The lead or lag is then related to the time of top dead center in terms of degrees.

Abstract: Apparatus for and method of determining the brake torque and horsepower of an internal combustion engine without connecting an external load. Means are provided to operate the engine at full throttle and with all but one out of n of successive ignitions inhibited, the value n being selected so that the engine operates with just enough power to equal the frictional load of the engine and maintain an equilibrium speed at the upper end of the engine speed range. The engine is then operated momentarily with full ignition, and then with no ignition, during which a determination is made of the rate at which the engine decelerates through the equilibrium speed. The deceleration rate is multiplied by the known inertia of the engine to determine the friction torque of the engine at the equilibrium speed. The friction torque is multiplied by n - 1 to predict the brake torque of the engine at the equilibrium speed when operated normally with external load. Horsepower is determined by multiplying torque and speed.

Abstract: Satisfactory or unsatisfactory engine compression is diagnosed by comparing the amplitude of the starter motor current, when cranking an engine having its ignition inhibited, with a reference value. The reference value is adjusted in accordance with the intake manifold absolute pressure, as determined from measurements during the test of ambient pressure and intake manifold vacuum.

Abstract: Means for and method of testing the power of an internal combustion engine. A tachometer means coupled to the engine generates one electrical pulse per engine cycle of the engine. While the engine is full-throttle accelerated, a computer means measures the time periods between successive pulses, each time period constituting the reciprocal of the average engine speed during the particular engine cycle. One-half of the time period corresponding with a low speed and one-half of the time period corresponding with a high speed are added to the intermediate time periods to determine an acceleration time period which is a measure of engine power. The acceleration rate is determined by subtracting the reciprocal of the time period corresponding with the low speed from the reciprocal of the time period corresponding with the high speed to determine the speed change, and dividing the speed change by the acceleration time period.