I have an camera that has its focal length animated to zoom in and im not getting any motion blur from this. Im getting blur from the camera transform and the objects moving but not the zoom.

I don't see how to establish motion blur based solely on the camera's changes in focal length and/or aperture, either.

Maybe it's got something to do with motion vector attributes. If Mantra really doesn't support built-in FOV motion blurring, you might have to introduce some frame blending during the compositing phase. Or just use camera transforms to move in closer.

http://www.sidefx.com/docs/houdini12.5/render/cameras [sidefx.com]