Abstract: An automotive data recording device for collecting data from a vehicle and for storing the data for further analysis includes a first electrical interface adapted to interface with a vehicle data terminal capable of supplying raw data internally monitored by a vehicle computer having a memory for storing the raw data. A volatile memory temporarily stores substantially all the raw data stored in the vehicle computer's memory, and a non-volatile memory stores a desired portion of the raw data. The device also includes a microprocessor programmed to provide a first control signal to retrieve the desired portion of the raw data from the volatile memory for storage in the non-volatile memory and to provide a second control signal to retrieve the desired portion of the raw data from the non-volatile memory.

Abstract: A diagnostic envelope is used to analyze measurements from an internal combustion engine. Measurements may be from a partially assembled engine during a cold test to detect subtle mechanical anomalies, or from a fully assembled engine during a cold test or a hot test (with active fuel and spark). The measurements represent vibrational amplitudes corresponding to various crankshaft angular positions of the internal combustion engine. The first step in generating the diagnostic envelope includes filtering the measurements to enhance local variations. Filtered measurements representing a number of engine cycles are then combined to reduce random cycle-to-cycle variations. The diagnostic envelope is then generated by subtracting corresponding measurements obtained from engines with known operating characteristics. The diagnostic envelope is used in analyzing and/or classifying the engine.

Abstract: A predictive model is derived for subsequent use in a misfire detector in an internal combustion engine. Data collected using a test engine is curve-fitted using NARMAX techniques to obtain a computational formula for the predictive model which relates deviant acceleration at the accessible crankshaft section to deviant acceleration at the inaccessible crankshaft section. Thus, the model can be used during actual misfire detection to reduce the effects of the torsional oscillations.

Abstract: Irregularities in crankshaft velocity introduced when measuring crankshaft rotation at a section of a crankshaft in an internal combustion engine that is less damped to torsional oscillations than is another more accessible crankshaft section are corrected using a NARMAX-generated model to predict rotation measurements that would have been obtained at the inaccessible section based on data actually collected at the accessible crankshaft section. Thus, the effects of torsional oscillations in the crankshaft are substantially filtered away, resulting in crankshaft acceleration values that form the basis of a misfire detector having nearly maximum signal-to-noise performance.