I can't remember exactly but the e-fan I have moves over 3500 CFM and it still lacked in keeping the motor cool enough. One thing to make note of is the air passing through the rad at speed with a e-fan goes everywhere.... through the fan, around the fan, sides of the rad. With a shroud the air is "funneled" directly on the block of the engine. A shroud plays a big role in engine cooling. I used to be a non believer that the shroud was kind of waste money but no longer. I really believe that a e- fan mounted as a puller centered in a shroud would be better.