If you go into the archives and search for "coolant flow meter", you will find a few posts on this subject including a brief description of my current system.

        If you go to www.gfsignet.com and search under "Flow" you will find that model #515 is a small paddle wheel sensor that slightly protrudes into the flow path, offering minimal resistance. Go to "Fittings" and you will find a large selection of available fittings for this. I made my own which wasn't hard but requires some aluminum welding & patience.

        Last year I was using one of the EM2's aux. liquid temp inputs to display this as a 0-100% flow with 100% = to ~40L/s. This was just to see how the automatic pump controller would react to various flight conditions. I don't currently have it connected as I'm now using that input to measure the cooled coolant temps.

Todd    (need more channels on my EM2)

Sadly, the pivotal instrument, a flow meter that doesn't disturb the
system too much, is probably not available.  If someone could come up
with a flow meter in a 1.25" line, we could do some expirements.