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Err, just noticed: Did you mean Eheim 1048, because the 1046 deadheads at 1.2 mH2O?
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I meant the 1046. 4' = 1.2m deadheaded. See my post above.
As for the rest:
You need to normalise the pressure drops at a certain flow rate that allows for a lowish margin of error first, and then map it back to the pump's PQ curve.
Remember pressure drop is proportional to the flow rate squared.
So revisiting your scenario, being the micra, be-cooling rad, and WW or MCW462B, we find that at a normalised 5lpm the pressure drops for each system is:
WW -> 0.7mH2O (rad), 0.2mH2O (tubing/pump fittings), 0.8mH2O (block) -> Total of 1.7mH2O
MCW462B -> 0.7mH2O (rad), 0.2mH2O (tubing/ pump fittings), 0.4m H2O (block) -> Total of 1.3mH2O
Now let's map that back to the Micra PQ curve.
WW system @ 2.2lpm => PD = 0.33m - and this matches up with the PQ curve for the Micra - predict 2.2lpm therefore
Modded MCW462B system @ 2.4lpm => 0.30m - and this matches up with the PQ curve for the Micra -> predict 2.4lpm
Looking at the C/W curves for the WW and the modded MCW462B at 2.2/2.4lpm respectively, and we find ~0.205 and ~0.235 respectively.
The WW is still clearly the better choice.
I think you need to check the axes on the Micra graph. They are litres per hour, and I think in a number of places you misconverted.