They should be  different in 1300 and 1600 (maybe more)
But blowing flow can be measured somehow and maybe somebody knows some numbers  
I´m planning to install 2 electric fans  on my type4   I thaught that  something like this:
http://cgi.ebay.com/ebaymotors/2X-9-UNIVERSAL-12VOLT-1550-CFM-REVERSIBLE-RADIATOR-FAN-/110749083674?pt=Motors_Car_Truck_Parts_Accessories&fits=Year:2010&hash=item19c928e81a
They are 1500cfm each   is it enough or not?  I would like to use it on street on summer when temp is +15 to +25c

and with those temps, why waste money on something else if the stock setup will work fine?

Seems to me that the late Dog House fan spits about 300 cfm at speed, while a 911 deal is closer to 1000cfm. Sound about right? I believe Jake Raby did some serious testing on fans a few years back, as well as Gene Berg years ago (but not the 911 fan conversion)...

heres mine untested yet



cheers andy

Excellent information! Saves a lot of time and tedious calculations ... plus this is 'real' data.
So now you know! WE know.

Personally, I think the advantage of the stock system may lie in the directional capabilities of the airflow; so much over the head(s) & so much over the cylinders (and that varies over its length).
From that perspective & with the electric fans, you may have too much over the bottom of the cylinder and too little over the head (practically none at the center section of the fan as the motor is there). Basically uneven flow as necessitated by the design of the engine itself.
The electric, radial fans may certainly work, but it seems the 'squirrel-cage' design fans are more reminiscent of the flow & directional characteristics of the original system.

TxT