milehigheric

Laws of thermodynamics and conservation of energy guys...Electric fans provide no 'extra' power assuming you are doing the same cooling job as the stock fan. When we are talking about loads we need to understand overall system efficiency.

Clutch fans use mechanical energy to spin the fan when needed. Electric fans use electrical energy to spin when needed which is supplied funnily enough by the mechanical energy in the first place. When it is transferred from mechanical energy to electrical (via the alternator) we actually waste energy, due to heat, noise etc. Our electrical systems run at 14.4V and the alternator will do all it can to keep it at that point. If we take a mechanical load from the engine and change it to an identical (same overall work) electrical load then the alternator will work harder. You actually use more mechanical energy (by the alternator spinning) just to cover the same identical load. This is also not factoring in inefficiency of the actual electrical fan itself either.

This is the reason our attempts at perpetual motion, nuclear fusion, cold fusion etc has not been overcome yet. To build a unit (doesnt matter what it does, or what its purpose it is for) that is greater than 100% efficient is seemingly impossible with current technology and scientific thought. In context, for an electrical fan to actually increase engine power both energy transfer (alternator) and the load (cooling fan) would need to be 100% efficient.

Any questions students

betelnut

Heh! Glad someone finally pointed this out. Anyone know how much of a load this puts on your alternator?

James Dean

Most fans only draw about 10-14 amps. About the same as a single off-road light or your high beams. I guess I need to turn off my DVD/NAV, lights, air pump and electric seat heaters.

90 percent of the time, our vehicle is moving and has no need for the fan to be running since there is already air flow. Only under load or while at idle do most electric fans turn on. Unlike clutch fans that turn all the time. This is where the load is reduced.

RustBucket

iTrader: (1)

The real question is how much energy does it take to shear the fluid in the fan clutch when the fan isn't running?

milehigheric

Really I thought that is why they were designed in the first place...to shut off when they were not needed, hence the word clutch.

10-14A is pretty substantial acutally. At 12V that is 168W...We loose at LEAST 30% energy in conversion from mechanical to electrical (roughly 50W in this case) bringing the power required to run an electric fan up to about 220W in total. For any power gains to be made would be to assume that the stock clutch fan uses greater than 220W in the first place. For those ludicrous claims of 10Hp gains would be to assume that the stock clutch fans actually consumes 7680W in the first place...crap if you ask me. With car manufactors extesnive R&D do you really think they would choose to install a clutch fan (that according to these claims) is up to 34 times less efficient than an electric fan? I didn't think so.

At the end of the day no direct comparison can happen without efficiency ratings of the clutch fan.

Tracey98277

well you can't use a mechanical fan in a front wheel drive. has anyone here ever tried Evens Watertless Coolant? they claim that there isn't even the need for a fan with their coolant due to its high boiling point. this would be the true answer to the inefficiency of a fan, just remove the need for it.

camo31_10.50

well idk about you dude, but my clutch fan is ALWAYS spinning...no matter if i'm goin 75mph or if i'm sittin in my driveway, and no it's not fubarred or messed up in any way thank ya very much.

and speaking from EXPERIENCE (not laws of thermo crap LOL )
my truck came with an electric fan, and i could take the hills between vian and sallisaw OK at 75mph no problem at all not losing any speed(and actually i could gain speed going up the hills)

well i replaced the electric fan with a new stock unit, and i couldn't hold speed going up the SAME EXACT HILLS!!!!!

that right there tells me that the stock clutch fan robs more power than you think.

to4menon4u

all the electric fan does is reduce resistance over the mech fan. the alternator may be working harder to produce the extra energy but the resistance it is creating is lower than a mech fan. as for how much less resistance? who knows but its enough to where you can feel a differance between the two ( maybe 3-4 hp )

drew303

......

Power gains, dream on. As someone else stated, when the fan is actually operating it's making the alt work much harder which is obvious when the fan kicks on and rpms drop (22r here).

Mech fans only actually do anything when your not moving, any forward movement and the fan is being driven by inflow. There is no HP gain between running a clutch vs electric.

The gain is in performance of cooling. I have a flex-a-lite fan on my 22r and it only comes on around 210F which the motor seldom hits unless im idling in traffic, drive-thru or wheeling. And the fan kicks on at an ridiculously obnoxious rpm (not sure what speed). And the motor cools down faster than ... insert your own perverted analogy here

Works wonders for cooling over a clutch-fan for wheeling and the option if you so desire to turn it off for deep water crossings is a SERIOUS bonus. Clutch fans spray the entire engine bay with mud and water and cause all sorts of issues in that manner.

I LOVE my E-fan =)

James Dean

Clutch fans don't ever shut off. They only slip or tighten depending on the temperature. This provides two benefits. 1-at higher rpms the fan isn't turning as fast and hard as the motor. 2-prevents the fan from becoming a solid object at certain rpm's (i.e. the speed the fan is turning would fight the natural air flow at certain speeds. This is the same reason why fan blades are usually staggered). There is still considerable drag on the clutch even after it has warmed up.

Flex fans and clutch fans are used mainly for three reasons. They are cheaper to make than electric fans, the motor is already turning (free drive system) and they used to be more reliable than an electric fan.

No you will not see major hp gains. You may feel a slight performance increase. Remember the only big draw is when an eletric motor starts (this usually happens at an idle), once it's running it draws very little power. Each one of my KC lights are 150w. So they draw about 11 amps each, 33 in total. I don't feel any hp power draw when they are on. Most cars run at 14 volts so your calculations can come down a little.

James Dean

Car manufactures have built non-efficient parts for years. Why do you think the aftermarket and performance market even exist. Intakes and exhaust are restrictive, incandescent lights are power hogs, interior wear out and break faster, etc. It's all about the Benjamin’s.

N204life

God bless America

camo31_10.50

thought i might revive this.

the stock clutch fan requires mechanical energy for it to work properly...so that means you have the alt. taking power from the motor, the fan, the A/C, and the Water Pump on some vehicles.


eliminate one of those, and you WILL see a gain.



want to make it EVEN MORE efficient????

then install an upgraded alt. that puts out around 90-110amps at idle!!!

THAT right THERE, will solve ANY of the "power" issues you guys TALK about.

like i said before, my '86 came with one and 235/75 tires..i could drive up some hills around my part of the country going 75mph or more...and maintain that speed or even GAIN speed....after i rebuilt the motor i put a new stock fan and clutch on it, same exact tires...and i was SLOWER going up the SAME hills...and couldn't hold speed and had to downshift to 4th gear....even had the SAME tank of gas!!!


my 3.0 fan TURNS at idle, but i can tell it's not spinning as fast as the motor is, so it's working!

irab88

iTrader: (4)

i saw a program about hyper-milers; people who squeeze every ounce of power out of the engine for the sake of fuel efficiency. what they do is disconnect the alternator (via relay) at higher speeds, leaving the electric fan to run off the battery alone. that takes all the load off the alternator. period. at slower speeds, they re-attach the alternator to charge the battery, or just charge it at home, and have no use for any alternator.

(these are also the people who switch to mechanical steering boxes to eliminate that pump, as well)