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Piston slap impact noise has been investigated using a piston secondary motion simulation. This simple model accurately estimates piston slap impact, by considering the hydrodynamic effects of the piston skirt oil film and the friction forces at various contact points. The results were compared with the actual piston motion measured by a link mechanism. Consequently, the calculation accuracy was confirmed to be sufficient to make precise estimates of piston slap noise.

This paper has clarified the noise generating mechanism on the BOSCH AD type fuel injection pump by using numerical and experimental analysis methods. The calculated vibration of each part has been verified to coincide well with the measured acceleration data. Based on the detailed analysis, the major noise source of the injection pump was found to originate from the tappet vibration caused by the steep pressure drop at the end of injection. After performing some parameter studies by using the simulation model, it turned out that some specifications of the injection pump influenced its sound power.

Recent progress in noise and vibration analysis technology had made great contributions to both noise level reduction and sound quality improvement in the interior noise of passenger cars. However, in spite of remarkable reductions in interior noise level, the sound quality in diesel passenger cars is still judged to be worse because of its different sound characteristics compared with gasoline versions. By using subjective testing, it was found that the main cause of poor sound quality in our test vehicle was the high contribution of relatively low frequency half-order multiple components, principally 2.5 and 3.5 order of engine rotation. The undesirable vibration transfer characteristics of the chassis was found to be one cause, but the half order components of powertrain vibration were also shown to be at a high level, and were the source of the excitation.

The authors developed a new method to calculate engine exciting forces by solving equations of motion using measured angular velocity fluctuation at the flywheel of the engine. Vibration response of a powerplant to the calculated engine exciting forces can be obtained by rigid body frequency response analysis with NASTRAN program using the measured value of the powerplant moment of inertia and the mount rubber characteristics. Calculated acceleration levels of a powerplant by this method were in close agreement with the measured ones. This method can be applied to estimate a powerplant vibration mode and levels when such parameters as engine mount locations are changed. As examples, the effect of reciprocating mass and cylinder-to-cylinder variation of fuel delivery were quantitatively discussed.