And this is what that very bottom test looked like running it against the heatercore. The heatercore is very restrictive for airflow, so most rads will probably have noticeably less pressure drop and result in more air flow than this, but it give you an idea.
http://img3.imageshack.us/img3/8294/...onradiator.png
I'm measuring the pressure difference on each side of the fan with the gauge and the air flow on the inlet side.
It's alot like a pump test, measuring the pressure difference relative to flow rate. It seems my last test is showing more of a prominent step in the curve. That's the sort of thing I'm interested in seeing and should show up alot better with the stronger fans.