Hi, I am familiar with these grainy renders. I agree with what DustRider mentioned. Also, it seems that IRAY likes light to render faster. You can add more light to your render by upping the Environment Intensity and Environment Map settings in the Render Settings. I have had success with upping one or both of these values. Then I use the Exposure Value in Render Settings to get the light the way I want just like a photographer would.

Jack238