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The dynamic behaviors of power-plant have much effect on interior noises and vibrations of passenger cars, especially, in the frequency range below 1000 Hz. So it is very important to estimate the vibrations of power-plant at the design stage. To predict the dynamic behaviors of power-plant including the rotating elastic crankshaft system, the time domain dynamic simulation methods have been applied, however such analyses require much time and resource of computer. In this report, the exciting forces to the cylinder block are derived in the frequency domain from both the dynamic stiffness of bearing oil films and the dynamic displacements of crankshaft journals, so that the computation time is reduced considerably. To estimate the displacements of the crankshaft journals, the vibrations of an engine crankshaft system including crank journal oil films under firing conditions are calculated using the dynamic stiffness matrix method in the frequency domain.

A series of NVH experiments were performed for a set of single cylinder engine models made of aluminum, with bore sizes of 100mm. Each engine model consists of a cylinder head, a cylinder block and a bedplate. Each has the same size of 150mm × 150mm, with different heights of 100mm, 200mm and 80mm, respectively. By choosing 112 measuring points on the structure surfaces, we performed a series of impact tests for the following cases, (a) The cylinder head and the bedplate were fastened to the cylinder block by two sets of ISO M10 Tap-bolts, each with the lengths l1=117mm and l2=97mm. (b) The cylinder head and the bedplate were fastened to the cylinder block together by a set of ISO M10 Through-bolts of grip length l3=380mm.

A series of NVH experiments were performed for a set of single cylinder engine models made of aluminum, consisting of a cylinder head, a cylinder block and a bed-plate. Each has the same outer size of 150mm × 150mm; the different heights are 100mm, 200mm and 80mm respectively. Those dimensions were determined following the dimensions for a diesel engine in lightweight commercial vehicle with the bore size of 100mm and the crankshaft main bearing diameter of 60mm. We chose 112 of measuring points on the structure surfaces and performed a series of impact tests, for the following cases: (a) When the cylinder head and the bed-plate were fastened to the cylinder block by two sets of four ISO M10 tap-bolts, each with the lengths ℓ1 =117mm and ℓ2 =97mm. (b) When the cylinder head and the bed-plate were fastened to the cylinder block together by a set of four ISO M10 through-bolts of grip length ℓ3 =380mm.