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Topic Review (Newest First)
07-14-2013 07:13 PM
Timelord83 Having swapped my Dodge Ram From a Clutch to a E-fan and my wrangler today. I can honestly say they have generous power gains. I have the 4L wrangler sport and 318 in my ram. I have an amperage gauge on my ram and both are thermostat controlled via a radiator probe. They turn on when X shut off when Y
On I took the wrangler for a spin today and with no one in front of me The fan came on twice both on steep grades otherwise it was off 90% of the time. I Plow with my Ram and it has an Air Compressor and winch I installed the AMP gauge to see how bad I was taxing the stock Alternator with the plow and E-Fans, plow is electric over hydraulic (I HATE IT But it pushes snow like a beast).

Also heats up quicker as there is no fan pulling air during a cold start, perfect for Vermont Winters.
07-14-2013 06:33 PM
Jerry Bransford Stay with your engine driven fan which definitely can move far more air through the radiator than an electric fan will. The only reason I would ever install an electric fan was if my TJ was in deep enough water enough that I would want to be able to temporarily turn the fan off before getting into deep water.

And there is no free lunch where an electric fan and more HP is concerned. Both a mechanical and electric fan both place a load on the engine. The electric fan simply places its load on the engine via the alternator which becomes harder to turn when asked to provide the additional amperes drawn by the electric fan. Which is why generators at dams require so much water pressure to turn... they have such a huge electric load on them that they are hard to turn.
07-14-2013 06:25 PM
freeskier
Quote:
Originally Posted by O_M_Jeep View Post
Anyone know how an alternator works? There are no little gears in there, it does get a little harder to turn as the power draw increases, but not as hard to turn as a 5 bladed propeller. I run directly off the battery, that's like feeding a water wheel from the lake, not the river.
Do you know why it get's harder to turn? The alternator stator is controlled by the PCM. The PCM monitors voltage. When voltage drops it increases the current through the stator, increasing the force of the magnetic field, and making it harder to turn.

As you probably know the alternator puts out 14 volts. It does this so it can charge the battery. When you hook things up directly to the battery it will NOT draw from the battery, it will still draw power from the alternator because the battery and alternator are wired in parallel. It WILL draw power from the battery when the load exceeds what the alternator can provide, which will cause a system wide voltage drop. Once the voltage drop reaches the voltage of the battery then power will start being drawn from the battery. This is typically only seen during winching.

Quote:
You don't get something for nothing, of course, no one said the power to run the electric fan is free, but the power to run the fan comes from a power storage source, the battery, and the whole point of this discussion is that the amount of engine power to run the alternator it's already turning is being taxed less by not having to also turn the fan.
Even if the above weren't true, where does the battery get it's power from?

Quote:
I know for a fact there is, with a 2.5L engine, a marked increase of available power when the engine doesn't have to turn the fan mechanically.
Lets now talk about the efficiency of an alternator. Alternators are maybe 60% efficient. Then you have the motor of the fan, which again is maybe 60% efficient. Every time you convert power from one form another you have an energy loss.

It all comes down to a very simple statement. If you have an electric fan moving 2500 CFM of air, it will draw more horsepower from the engine than a mechanical fan moving 2500 CFM of air. It's that simple. There's no arguing it.
07-14-2013 06:03 PM
O_M_Jeep Anyone know how an alternator works? There are no little gears in there, it does get a little harder to turn as the power draw increases, but not as hard to turn as a 5 bladed propeller. I run directly off the battery, that's like feeding a water wheel from the lake, not the river.

You don't get something for nothing, of course, no one said the power to run the electric fan is free, but the power to run the fan comes from a power storage source, the battery, and the whole point of this discussion is that the amount of engine power to run the alternator it's already turning is being taxed less by not having to also turn the fan.

I know for a fact there is, with a 2.5L engine, a marked increase of available power when the engine doesn't have to turn the fan mechanically.
07-14-2013 05:45 PM
Ironhead Jed
Quote:
Originally Posted by Jeffreybomb View Post
We're not thinking it's "getting something for free." Obviously, the fan has to run and it needs power. However, we were thinking that if the fan is disconnected from the engine and given electrical power instead, it would allow the engine to provide more power to other components.
the problem is one of the components that it would be powering is the alternator, which is now requiring more power due to the electric fan
07-14-2013 05:31 PM
Jeffreybomb We're not thinking it's "getting something for free." Obviously, the fan has to run and it needs power. However, we were thinking that if the fan is disconnected from the engine and given electrical power instead, it would allow the engine to provide more power to other components.
07-14-2013 03:07 PM
00silverTJ
Quote:
Originally Posted by O_M_Jeep View Post
The laws of thermodynamics? lmao, show me the math. I know what I have observed, not on paper, not an equation, not even a theory, but the practical application.

So, unless you have tried and experimented with the differences between application of available power with the electric vs mechanical variable, then I don't guess I put much stock in your theoretical opinion.

But seriously, you use the three laws of thermodynamics and show me the math, here, I'll help you get started - Physics4Kids.com: Thermodynamics & Heat: Laws of Thermodynamics
His response would seem obvious to me. Put a fan on an engine and let it blow;

Or, run a belt from the same motor to an alternator; let it generate electricity; run that electricity to a battery, then feed a fan off that battery.

I don't know anything about thermodynamics but I am old enough to have heard the saying " nothing comes for free" a gazillion times, and actually let it sink in.

So I don't see how the electric fan could provide an overall increased level of efficiency. I think that is what he was getting at.

Increased amperage draw means increased alternator demands, means increased engine demands, means increased heat, means increased demand on the fan; and so on.
07-14-2013 02:48 PM
Jeffreybomb
Quote:
Originally Posted by Ironhead Jed View Post
in theory, if there is a power increase, it would be much more noticeable on a 4cyl than a 6 cyl
Yeah, that's what my buddy thought, too.
07-14-2013 02:46 PM
Ironhead Jed in theory, if there is a power increase, it would be much more noticeable on a 4cyl than a 6 cyl
07-14-2013 02:33 PM
O_M_Jeep The laws of thermodynamics? lmao, show me the math. I know what I have observed, not on paper, not an equation, not even a theory, but the practical application.

So, unless you have tried and experimented with the differences between application of available power with the electric vs mechanical variable, then I don't guess I put much stock in your theoretical opinion.

But seriously, you use the three laws of thermodynamics and show me the math, here, I'll help you get started - Physics4Kids.com: Thermodynamics & Heat: Laws of Thermodynamics
07-14-2013 01:57 PM
freeskier
Quote:
Originally Posted by O_M_Jeep View Post
I have a 2.5L, I switched from the mechanical to an electrical fan, I have never had any trouble with cooling, and I do have a kill switch for the fan, I have never had any alternator issues and I don't run it off of a thermostat, when the key is on, the fan is on (unless the kill switch is off). What I noticed the week I switched back and forth, one, then the other, then back, then both, looking at behavior is this - with an electric fan I have measurably more power, with the electric fan I could use 5th gear in places I couldn't with the mechanical, I could maintain speeds better. I don't know how much more power it gives, I don't watch mileage, I don't own a dyno, but I know in the real world on the street and on the trails, the electric fan cools just as well if not better and gives a nice return on available engine power.

I will also say that as well as not running it through a thermostat I also do run it straight from the battery through a relay, perhaps that is why I have never had any alternator trouble or loading.

I use a $70 O'Rielly fan and a $5 relay and a $12 switch, no trips to junkyards, no thermostats to wire, no $1000 systems, simple, easy, and damned effective.
That statement right there breaks the laws of thermodynamics. An electric fan will ALWAYS require more energy to pull the same amount of air through the radiator as a mechanical fan. The only reason an electric fan has a net lower energy use is because it can completely turn off when not needed.
07-14-2013 01:29 PM
O_M_Jeep I have a 2.5L, I switched from the mechanical to an electrical fan, I have never had any trouble with cooling, and I do have a kill switch for the fan, I have never had any alternator issues and I don't run it off of a thermostat, when the key is on, the fan is on (unless the kill switch is off). What I noticed the week I switched back and forth, one, then the other, then back, then both, looking at behavior is this - with an electric fan I have measurably more power, with the electric fan I could use 5th gear in places I couldn't with the mechanical, I could maintain speeds better. I don't know how much more power it gives, I don't watch mileage, I don't own a dyno, but I know in the real world on the street and on the trails, the electric fan cools just as well if not better and gives a nice return on available engine power.

I will also say that as well as not running it through a thermostat I also do run it straight from the battery through a relay, perhaps that is why I have never had any alternator trouble or loading.

I use a $70 O'Rielly fan and a $5 relay and a $12 switch, no trips to junkyards, no thermostats to wire, no $1000 systems, simple, easy, and damned effective.
07-14-2013 01:12 PM
jeepwayoflife
Quote:
Originally Posted by Jeffreybomb View Post
Thanks for the insight. Does an electric fan ease the load on the motor and would that be a benefit to engine performance?
Technically then it would simply put more of a load on the alternator, making the engine work harder for that. In the end you might gain a couple HP if anything.

The reason people do electric fan swaps is so they can turn them off for water crossings where normally the clutch in a mechanical fan would be ruined.
07-14-2013 12:33 PM
Jeffreybomb Thanks for the insight. Does an electric fan ease the load on the motor and would that be a benefit to engine performance?
07-14-2013 12:24 PM
Ironhead Jed i was skeptical on the answer i am giving for some time. my previous background was all street rods and muscle cars, where electric fans can add a good amount of cooling assistance. on a TJ, it just isnt there. There are a thousand threads about this and after reading through tons of them, it seems like there is no justifiable increase in cooling performance.

a few things that i have noticed as differences that could be the reason for a difference in our jeeps

we have a very square radiator when compared to most vehicles. our fan shroud doesnt direct as much air towards the stock fan as in a more rectangular shroud. most of the air is pulled straight through the radiator instead

we have very large grill openings when compared to most vehicles

our engine bays are very open compared to most, which helps air flow past the radiator and out of the engine compartment

there are other things that equate as well, but i feel these are the biggest factors in the argument for stock clutch cooling. IMHO, your money would be better spent on some hood vents to help get the hot air away from the radiator at a faster rate
07-14-2013 12:12 PM
Jeffreybomb
Clutch driven vs. electric fan?

A buddy of mine (non-Jeeper) noticed the clutch-driven fan on my TJ. He told me I might benefit more from an electric fan, but he wasn't 100% sure because he's not into Jeep. He suggested I ask if there's a benefit to switching to an electric fan?

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