Here's my post with the ipmi hex command which helped me: serverfault.com/.../132958
I added a PCIe card to my r730xd.  The fans went from 3,800 RPM to 17,000. The Lifecycle log showed: The suggested solution to this is:  If a lower fan speed is required, contact your service provider for the appropriate IPMI commands to reduce the default fan speed response for new PCIe cards. I have been working with my local Dell service contact but they so far are not able to provide me with the IPMI sequence I require to not scream the fans.  FWIW, my t410 has the pair of this card (a Mellanox 40/56GB dual port card) and it has not adjusted the fans in the least.  Mellanox describes this as a low power card.  Whenever I remove it from the screamer, the heat sink is not even warm to the touch.   Anyone have any luck getting this info? 
r730xd excessive fan speed