A passenger vehicle onboard computer system for engine fault diagnosis, performance measurement and control

This paper describes a microprocessor based on-board instrumentation system with applications to engine fault diagnosis, performance measurement and control. A non contacting measurement of engine angular position, taken at the flywheel by means of a magnetic sensor, provides a signal proportional to crankshaft angular velocity. The signal is then appropriately digitized and interfaced to a microprocessor, along with timing information regarding engine position. Suitable processing of the signal by the microprocessor provides information in real time regarding crankshaft speed and torque nonuniformity, which is employed to detect engine faults and to yield a measure of engine performance. Experimental verification of a prototype instrument has been carried out on the road in a number of vehicles, with very successful results. A variety of experiments have confirmed the usefulness of the system for applications in fault diagnosis and performance measurement, and the potential of the system for some aspects of engine control.