The search for more and more sophisticated models for the dynamic behavior of cars, mainly for the prediction of their acoustic properties, leads to modelling of very complicated parts of the vehicle such as seats, exhaust lines, etc... We show in this paper how to test the validity of the models and describe the tools developed at the PSA-Peugeot-Citroen/LMARC to both improve the accuracy and reduce the size of the finite element model. Firstly, the methodology used to prepare and validate the models is described. Secondly, we show how to update the finite element model of sub-components by comparing the measured dynamic behavior to the predicted one. Thirdly, two ways are proposed to simplify the models for sub-components: the first one consists in condensing the stiffness and mass matrices on the boundary degrees of freedom. It leads to a simplified mathematical model. The second one, devoted to hollow girders and tubes, consists in the determination of an equivalent beam having the same dynamical properties. This second method has the advantage of preserving the physical meaning of the model. The capabilities of the proposed methods are illustrated by a few examples coming from the car industry.
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