I am using the Define R4
not Mini - but so I dont have to remove my motherboard? - I can just turn the heatsink? - and I need to remove exhaust fan or is it necessary in the Define R4?
Yes, you can just turn it, but do remember to apply new thermal paste, if you do not, you will likely get air bubbles caught between the CPU and heatsink, that is why you need to reapply, even if the heatsink has just been removed briefly.
You will still want to run the rear exhaust fan to remove hot air from the case and improve air flow.
And yes, looking at it again, I can see that it is the Define, just took a quick look before and just noticed the top 4 white pci brackets =) well, brainfart hehe