D5 vario cooling influence

I found this while poking about the interwebz.

http://www.dazmode.com/_Reviews/2010/FLOWTEST.htm

I apologize if it is old but it is very interesting. Basically shows the speeds of the pump in the vario (not overall, there must be some speed, obviously) make very little difference.

That holds true until you get below about 1 gpm or so, then the temps curve will rise fairly sharply. You need to keep the minimum flow rate above a certain minimum level, which for most waterblocks is around 1 gpm. You can see the curves on that waterblock in your linked test here at skinnee's pages for an example.