Ok I spent today running a flow test to see how well I could estimate W from deltaT across waterblock. Numbers are tabulated
HERE
At low flow rates, I think W is reading low because the temp probe on outlet side is about 2' from the wb outlet. I am going to replumb so that it is only a few inches away. For really high flow rates then you have a different problem: 0.001C res is needed as 0.01C translates to roughly 9W at 2.25GPM. If you average 1.25-2.00GPM W then you get 81.53W. That's in reasonable agreement with your 2200MHz and 1.85V results (I am running 2200MHz and 1.85V Bios/1.81V in mbm).