I'm gonna disagree on you on this. The Derale fan shroud stands off the radiator at least an inch creating a plenum that will allow the fan to draw air across the entire radiator, unlike the pusher setup right against the radiator, that literally only uses the diameter of the fans footprint over the rad core when standing still. When the fan is running, it is moving air, and air will take the route of least resistance out the fan, that includes ALL the air in the shroud and that air has to be replaced with air across the radiator core. No pressure buildup when he fan is running. Electric fans also regulate temperature better than a mechanical fan as they can be controlled by thermo switches. It does not have to be on when the motor is cold start up, the duals usually have a dual fan controller that will have one running while the other one is only kicked in when the temp goes over a preset value. A mechanical fan never disengages, doesn't work when the motor is turned off (heat soak) and runs full blast at WOT when you probably dont even need it as air across the rad is a given. One guy saw a 3.85% gain in HP and 8.93% gain in Torque going from clutched mechanical to electric. Whats a ~4% gain of HP on your motor? 9% torque gain? Even though the electric fan is causing more drag on the alternator, its still way more efficient than the mechanical fan. I understand some guys wont use them (as noted) but you can't deny the benefits of the electrics over the mechanicals.
