Run electric fans all the time?

AJ/FormS said
I'll try to be as nice as I know how, about this;
I'm guessing you have no idea how alternators work. Electric fans are not zero energy devices.
I know nothing about electric fans, just like I know nothing about a lotta things, and I freely admit it. I have heard that the better fans draw 40 amps, so if that is true, then; at 40amps x13.5volts, they suck 540 watts or .724 horsepower net. But alternators are only maybe 10 to 20% efficient so really, .724/.15=4.83hp gross. If you have 2 of them, that's 9.65hp. And how much does the controller burn up? This energy has to come from somewhere, and the alternator is it.

But wait it gets better, In traffic at sub 30 mph, your fans could be both on, sucking all that 9.65hp from your monster engine, now idling along at the same 25hp, everybody else is moving at. Ok so 9.65/25=39.6% of your crank power is going to driving the fans. Gee that's 3.168 cylinders worth...... over 3 cylinders. So, you don't notice it cuz you just open your throttle a lil more. But it shows up at the pumps, all the same.

So what's the advantage to electric fans?
On the street for a street-only type car,cooling wise, there is no advantage.
At the track, being able to set them on max, in the pits, yeah, that could be an advantage.But my all steel, 7-blade, hi-attack angle, thermostatically controlled clutch-fan, keeps my engine at a constant 207*F no matter the circumstances, so...... no advantage to me.

After 35/40mph, for a streeter, neither fan even needs to be there, cuz ram-air is, has been, and will continue to be, the primary cooling force, pushing air thru the rad, rather than pulling.
Try to think of it this way; After 35/40 mph, my mechanical fan is in danger of being a restriction to cooling. But if I drive a lil faster the air pressure coming in could start to power my fan into generating power, just like a wind-turbine. Can your electric fans do that trick? lol. Well, no, um, they're not connected to the crank, and um, they're not even on. Think about it. The Earth is not a sphere. think about it.

DrCharles said
A quick Google shows that a typical car alternator is 55% efficient, not "10-20%". Also, 40 amps is what the well-regarded Contour fans draw when both are on full speed. No one would ever have two 40 amp fans.
So your 9.65 hp drain is WAY overestimated. That'd also be pretty hard to transmit through a single small V-belt going around a 2.5" pulley...

Again, you couldn't be more wrong. Except maybe about not knowing anything. I do know how alternators work, fans work

I tested my own setup at full speed sitting in my garage, and it draws 20A when running, verified with an inductive clamp multimeter, but most of the time its going to run at the lower speed which is 15A. So 15x13.5=202.5W. Then we convert to hp by dividing by 745.7 = 0.272 hp and then remove alternator efficiency at even for the benefit of the doubt, 50% efficiency, 0.544 hp loss. So even the most bad *** electric fan anyone can think of costs about 1hp. Inrush current is 35-38A to start from a stop but that is in the range of 1 second. The battery will take most of the hit there.

Your mechanical fan takes more than 1hp to turn always. The efficiency is not there with a mechanical fan which is why they have basically disappeared from anything modern.

The fan isn't generating power when you go a little faster. It's still a cost, its rotating weight attached to the crankshaft that you have to accelerate anytime the RPM increases. You would be indicating that air passing 90 degrees over a device running at a certain RPM is making the fan spin and applying power to the crank, which is not happening. I'm sure there is a condition where there is some amount of drag loss on the fan which would reduce the amount of energy you lose by moving it. Not any real way to quantify, but I'm driving down the road and the electric fan costs me literally nothing because its literally not on and not spinning. The RPM of an electric fan is also decoupled from accellerating or decelerating the engine.

My engine is also running a lot cooler than 207F. Going down the road its 180-185 and the fans turn on at 195 and off at 192.