Mechanical Fan VS Electric Fan

Revhendo,

"So, perhaps a better test would be to see how much airflow is required for your cooling system to operate efficiently and plan your fan set up from there?"

Agreed.

Additionally I would not imagine that the factory fan system would be overkill to the extent that it needs revision. There would be no reason for the factory to produce a significant overkill on a system. Secondly it is stone reliable. Then add on the increase in performance of the modified engine and it seems reasonable that a person would not be interested in less than factory cfm.

"The implied massive and equalizing load that you are talking about on the alternator would only be imposed by an electric fan of the same cfm rating working at the same rate as your beloved mechanical clutch fan."

True. I do love mechanical fans. I also very much like a lot of the awesome electrical fan setups posted here as they really look aerospace and bad ***. I agree with your statement above that the best test would be to determine the optimum cfm and water flow for an application.

"With an electric fan, you reduce the the mass of the fan/clutch/pulley/belt/bolts/dust/six bugs/whatever from the engine."

I partially agree.

Every time the elec fan cycles it burns energy getting up to speed so that is load. While it is running of course that is load. You still have a pulley and belt on the water pump so that rotational inertia is the same on those components even if you delete the clutch fan. In an electric fan scenario you have considerable loss of energy in translating rotational energy to electrical energy in the alternator then back to its original state in the elec fan motor. So there is loss of efficiency that cannot be applied to generating cfm. Simply changing to a modern plastic fan blade such as on a ford ranger could alleviate the stigma of a moderately efficient factory metal fan blade further increasing the net efficiency of a clutch fan set up.

I would be willing to bet if you had an electric fan that pulled the same as the stock clutch fan it would burn more horse power if you averaged it out over a 10 hour period.

I could of course be very wrong due to other factors that I am not accounting for. One could be that in an efficiently designed air flow system where an air dam and bumper contour promotes great air flow thru the radiator during driving speeds, an electric fan can completely turn off for potentially hours at a time producing zero crankshaft drag and make up for its inefficiencies, operating only at low vehicle mph. Not sure if that is a real world scenario though.

I still say that the only reason an electrical fan would use less energy is because it is yielding less work (cfm) therefore requiring less energy input. Same concept with an electric water pump.

Like you said, the question is how much yield is necessary to properly cool the engine in the application.