In VRAYforC4d you can add a Vray Motion Blur Tag to have extra control of motion blur of objects.
Name – here you can enter a name for the object.
Layer – If an element was assigned to a layer its layer color will be displayed here. This field reflects the layer color in the Layer Palette. You can drag & drop layers from the Layer Browser or similar layer fields onto this field. You can also assign layers or remove elements from current layers using the menus located behind the small triangle.
Deformation Blur – support of motion blur for deforming objects.
Motion Blur Samples – this value determines number of samples VRAYforC4D takes into account when blurring the current frame. Increasing this value produces smoother results at the cost of increased rendering times.