Well...got curious/bored, ran a few tests.
I have a Delta 2600 RPM "Cessna Propeller"
, the 1800 RPM ECO stock fan (that they say was custom designed for this application), and a random Coolermaster red LED case fan...I estimate it around 1200 RPMs.
First off...having a slower push fan didn't seem to make much difference with either the stock ECO fan or my high RPM Delta, except perhaps some mild noise increase. I tried it both ways, on and off.
The 1200 RPM case fan pushing by it's self was not very efficient...as expected. There was a lot of blow back as air would rather back up then fly through the radiator. I know...duh
The Delta 2600 RPM fan in a pull config did the best, but also gave me a mild headache. It's so loud at that speed.
The factory ECO fan at 1800 RPM did very well, falling just ~2 degrees (Celsius) short of the Delta.
I noticed the factory ECO's fan blades have a better pitch and a bit more blade area, most likely for a mild compressing effect to help pull air through the radiator. I don't have any other radiators running around my house right now, but from memory this one looks to have a tighter fin pattern.
So, everything is exactly like you might think...if you paired up 2 super-kick-*** fans in a push<>pull I'm sure this device would perform better. duh
But the factory ECO fan does seem optimized for the best of both worlds, performance and silence. I wish I had the money for a pair of really quiet performance fans...as I bet that would be fantastic.
All be told, the factory fan in a pull is probably your best bet, short of spending lots more $$$ on a pair of good after market fans. Even still, I doubt you would see more than a 5 degree difference....if 5 degrees means that much to you, I suggest going full water and building a loop.
