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This paper describes the method to detect S. I. engine misfire for the OBD II requirement. In most methods related to the misfire detection, the fluctuation of crankshaft speed is used as an input parameter[1, 2, 3, 4 and 5]. If the misfire detection is performed by the pattern of crankshaft speed without considering the engine dynamics, it is difficult to determine the misfire at high speed and low load condition. So this paper proposed the single degree of freedom energy model of engine dynamics for the misfire detection. Through this model the integral of torque by cylinder pressures are estimated using the variation of crankshaft speed and it is possible to detect the misfire by this integral value.

This paper describes to measure the cylinder pressure in a SI engine using the variation of crankshaft speed. Assuming engine dynamics as a single degree of freedom the energy equation is derived. Through some assumptions each cylinder pressure can be estimated form the pressure torque. Through this study cylinder pressures by this method show good accord with measured value in low to medium speed ranges. For more accurate analysis the crank angle based modeling of friction and vibration is required.

To clarify the atomization characteristics of transient diesel spray droplet size distribution of spray was measured and Sauter mean diameter (SMD) was also calculated using the optical method based on Fraunhofer diffraction theory at different locations along the spray axis and at different time from the start of injection. To investigate the effects of various operating parameters on drop sizes the injection pressure and the density of gas phase into which spray injected was varied. At each location of spray the timewise measurement of SMD showed its peak value at initial stage and gradually decreased to reach an almost constant value noting that the fully developed spray and droplet - gas equilibrium were being approached. This indicated that the atomization of spray was not a process that ended as the liquid left the nozzle exit but one that continued in time and space.