Abstract: Substantially instantaneous, sub-cyclic speed of an internal combustion engine provided by clock counts between successive sensing of integral numbers of teeth on the flywheel of the engine provide plural speed indications within each cylinder stroke engine sub-cycle, which are utilized relative to each other, without conversion to speed dimensions, to determine dynamic, sub-cyclic operating parameters of the engine, such as relative power contribution of the individual cylinders of the engine.

Abstract: Diagnosing an internal combustion engine includes full throttle, specific speed tests such as measuring fuel pressure at two checkpoint speeds and at rated speed, and determining the pressure and speed where the governor reduces fuel pressure, an aneroid checkpoint of fuel pressure as a function of engine speed, and a fuel inlet restriction test, all without a dynomometer. The tests are performed with the throttle wide open, so that pressure can be measured downstream of the throttle at accessible taps, and/or to provide maximum fuel-flow test conditions. The speed comparisons are made during an acceleration with the throttle fully open, the instantaneous speed of which is accurately determined by flywheel tooth sensing.