[Shepherd777]

Originally Posted by drmiller100

Be VERY careful about the rpm you try to spin it at. Axial flow fans (traditionally a boat's propeller, but a traditional car fan sort of acts like one) the amount of air is a function of the RPM, the diameter, and the pitch of the blades.

An aside. What would be REALLY cool would be to drive the fan with a hydrostatic pump - the logic would be to measure exit temp coolant out of the radiator, and drive the fan faster until the coolant temp drops.

Horton made me sign a waiver not to operate the fan higher than 2200 rpm's. So I know it is good for at least that. But that high an rpm in this truck is a moot point. We will be operating the 450hp Cummins diesel in this truck just like an electric motor. That is, at almost a constant speed, in the most optimal range of 1100-1300 rpm. Procedure: go up a hill, drop to 1800ft. lb. torque peak @ 1100 rpm, split the 13 speed transmission to the next lowest gear, rpm's will climb to only 1300, go up the hill some more. Rinse & repeat. No grade rpm @ 55mph will be 1150, if I remember the math correctly.

Horton has supplied the hardware and software for a viscous unit. The WindMaster Revolution fan is controlled by Horton's wonderful Stratis viscous device. And the Stratis is also a very intelligent fan clutch. Fans and Fan Drives - Stratis® / Viscous Fan Drives | Horton It constantly monitors the engine computer (ECM) and if the engine only needs 5% cooling from the fan, that's all the fan puts out. Why use that other 95%, and waste all that fuel, if you don't have to?