[RocktimusPryme]

Super Cool information. I think the fact that companies kept using engine driven fans on heavy duty trucks well after most cars dropped them shows how well they perform in certain situations.

But to add to the conversation, I think people often don't frame the electric vs mechanical fan argument correctly.

Most people who have cooling issues on old cars with clutch fans, have them at stops and low speed traffic. Im not saying you can fix this, but to me, this is where an electric setup shines. They arent RPM dependant like an engine driven fan is. You can have all the beans the electric fan can provide at a low RPM where the engine driven fan cant spin faster than the water pump. At a certain point I don't know how much dead max airflow matters. Once its adequate, its adequate. The bigger decision point might be, which setup can give me the most airflow when I need it?

Now I have head horror stories of people going to electric fans and the problem flipping, all of a sudden they get hot at highway speed, but I think that is a matter of the shroud not letting enough air through. I think your testing shows that clearly, which the openings and the fans blocking said opening being an airflow limiting factor. Which is pretty easily fixed with those flaps that you see with some OEM shrouds and the higher quality aftermarket units.

Aside from the obvious mistake people make with buying inferior electric fans to start with, I think that is probably the biggest mistake people make in going electric. Shroud airflow at highway speed.

Side note. I have this enormous Bosch electric fan with shroud I bought from a swap meet for $5. I believe its from an early 2000s Mercedes C230. Its 19.5 inches, the same size as the big bad AC GM clutch fans. I can wire it to come on full blast, it even has a built in slow start. But it has 4 wires, a large ground and large hot, that I believe is meant to always be hot. Then another smaller wire when given 12 volts signals on. The 4th wire I assume is meant to be PWM speed controlled.

Ive been trying to figure out an easy way to make it work because I think it could be the new Lincoln Mark VIII fan if I can. I even bought a cheap PWM controller which I can make work when I put it on the big wires to control speed, but I think the speed should be controlled by that 4th wire.