While I was making the new fan shroud for my 949 Supermiata radiator and FM spec SPAL fans I took the opportunity to collect some relevant data to compare the 12" EBAY fans that I had on my old EBAY radiator to the smaller and bigger SPAL fans that are specced for the FM high air flow fan kits.
I hooked each fan to my battery charger, used a model airplane power/amp meter and Magnehelic gauge to measure the DP across the radiator with each fan.
Small Spal fan (3010.1522) 0.48" H2O, 9A, 11.3V
Big Spal fan (3010.2029) 0.50" H20, 9.5A, 11.25V
EBAY 12" fan, 0.25" H2O, 5.5A, 11.6V
See the pictures below of the measured DPs.
These SPAL fans were bought used and I have had the EBAY fans on the car for a few years so I am not comparing a new SPAL to a used EBAY fan. No matter how you slice it, that is half the DP which equals half the flow for the EBAY fan versus the SPAL fans. The SPALs make a ton more noise too and it is easy to tell they move more air.
I wish I had the time to dig up my factory fans and hook them up for a comparison.