[BillA]

and I had hoped a technical field might buffer me from economics, fat f***ing chance that

re testing fan/rad assys, not so many combos really
base (for heater cores only today) is fan on fins
2ed is ~1/4" standoff (built into all 'computer' rads)
3ed is greater than 1/4" (no measurable dissipation increase however, why bother ?)

some w/o data may theoretically contest #3, but I've confirmed such now with 2 separate benches and numerous rads
the convential rot is 1/2 the fan dia, but also at that distance I can measure no increase over 1/4" (our little muffin fans ?)

my question was: if measuring the differential air pressure (in 1/4" plenum to ambient/rad backside), will that nominally equate to a point on the fan's PQ curve ?