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Twilightoptics
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Joined: 13 Jan 2004
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Location: Auburn , WA

1987 Chevrolet Camaro IROC-Z

PostPosted: Mon Aug 12, 2013 9:09 pm    Post subject: Reply with quote

The load a e-fan puts on the alternator is FAR less drag on the engine than a clutch fan engaged. That said, clutch fans tend to come on WAY late IMHO where as an e-fan comes in sooner. Hotter engine = more efficient but less power.... so what do you want?
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aaron_sK
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Joined: 23 Jan 2006
Posts: 8834
Location: Back in beautiful Tacompton

1987 Chevrolet Camaro IROC-Z

PostPosted: Mon Aug 12, 2013 9:17 pm    Post subject: Reply with quote

Twilightoptics wrote:
The load a e-fan puts on the alternator is FAR less drag on the engine than a clutch fan engaged.


That's the commonly held belief, but I've never bought it.

It seems to me that if you move the same amount of air using the same means of power (gas burns, fan turns, air moves) then the energy usage would be about the same. There is not some massive loss of energy in heat or anything.

Doesn't make sense to me, but I'm not an engineer, merely a drunken idiot. Wink
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Twilightoptics
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1987 Chevrolet Camaro IROC-Z

PostPosted: Mon Aug 12, 2013 9:21 pm    Post subject: Reply with quote

There's moving air, and there's moving the equipment. Clutch fan has much more rotating mass than your simple electric fan that needs to be light to keep the amp draw on the motor down.
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QwkTrip
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Joined: 17 Feb 2004
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Location: Peoria, IL

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PostPosted: Mon Aug 12, 2013 9:24 pm    Post subject: Reply with quote

aaron_sK wrote:
I'm more interested in the fact that you still get freakin' magazines!


If you want to quickly research something then electronic media is great. But you still can't beat the fun of finding a new magazine in the mail and relaxing on the couch!
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QwkTrip
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PostPosted: Mon Aug 12, 2013 9:35 pm    Post subject: Reply with quote

Alternator is about 80% efficient. And then the electric fan motors are another loss (not sure the efficiency of the fan motors).

I think my article was a single fan vs. single fan. Aaron, do you even have the option of using dual fans with duty cycle management by an ECM?
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aaron_sK
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1987 Chevrolet Camaro IROC-Z

PostPosted: Tue Aug 13, 2013 7:39 pm    Post subject: Reply with quote

Twilightoptics wrote:
There's moving air, and there's moving the equipment. Clutch fan has much more rotating mass than your simple electric fan that needs to be light to keep the amp draw on the motor down.


With the big old steel clutch fans I could see an argument being made for rotating mass, but the new clutch fans are all plastic and the clutches are much smaller than the old ones. On the other hand my Taurus e-fan and two-speed 40amp motor are heavy! Laughing

QwkTrip wrote:
Aaron, do you even have the option of using dual fans with duty cycle management by an ECM?


It seems plausible that you could make MS control two fans, but it doesn't really make sense to so since you are burning a lead from the ECM to do something that a ten dollar thermal switch can do. I am not even sold on the idea that I will need the second speed on this fan. I will run the car with the ECM controlling only low speed and see how the temps are.

Even on GM's dual fan cars, one fan is always triggered by a thermal switch and/or the aircon.

TL;DR warning:

I would bet that at simply moving air (especially a lot of air) a clutch fan would be far more efficient than an e-fan because it doesn't suffer energy loss from wiring resistance or alternator and motor inefficiency.

A clutch fan never has zero drag (even when the clutch is disengaged), it cannot be disengaged above a certain speed (when it is useless due to airflow) and when the engine is at it's most inefficient (cold start) it is locked on until the RPM rises enough to disengage it. That cold start and constant drag is where you see energy loss. Stuck in traffic on a hot day the e-fan is wasting your gas compared to the clutch fan.

In my mind a clutch fan is like a carburetor. People on the internet argue about which is "better" but it's subjective. In some applications it is better than EFI. I don't mind having a carb, I know and understand them, but when I build a car an e-fan and EFI are just easier for me so that's what I run. Cool
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Alphius
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PostPosted: Tue Aug 13, 2013 9:35 pm    Post subject: Reply with quote

aaron_sK wrote:
It seems plausible that you could make MS control two fans, but it doesn't really make sense to so since you are burning a lead from the ECM to do something that a ten dollar thermal switch can do. I am not even sold on the idea that I will need the second speed on this fan. I will run the car with the ECM controlling only low speed and see how the temps are.

Even on GM's dual fan cars, one fan is always triggered by a thermal switch and/or the aircon.

It is fairly arbitrary to add outputs to the MS, if you wanted two-speed control it would be easy to wire up.

I can't speak for anything else, but I know on LS1 F-Body cars the dual fans have three modes, all ECU controlled. No fan activation ever happens by a temperature switch.

Off
Both fans slow speed
Both fans high speed

They also do have an A/C on mode that is controlled by the ECU, but that's not really relevant to the discussion.

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Twilightoptics
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1987 Chevrolet Camaro IROC-Z

PostPosted: Tue Aug 13, 2013 10:54 pm    Post subject: Reply with quote

Plastic clutch fan is still larger and heavier. Has to move more air at low rpm. E fan just goes.

40amp? That doesn't seem right. Both my big nasty mr2 fans measure less than 10a together and they were designed one for cooling one for ac.

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91RSVert
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1991 Chevrolet Camaro RS

PostPosted: Fri Aug 16, 2013 2:13 pm    Post subject: Reply with quote

When I went hunting for an efan a few months ago on summit. It asked how many amps I wanted it to draw. I'm going to ASSUME that the more amps it draws, likely the faster and more are it would move. But I do know that also depends on the design(s) of the blades.
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Alphius
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PostPosted: Fri Aug 16, 2013 2:37 pm    Post subject: Reply with quote

My dual IROC fans draw well over 30amps for a second or two under startup load.
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aaron_sK
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PostPosted: Fri Aug 16, 2013 4:01 pm    Post subject: Reply with quote

I don't have an ammeter that will read high enough so I can't test it myself, however the factory Ford harness has a 20amp breaker on the low speed side and a 40amp on the high speed side.

Here's a test of a later single-speed Ford fan:

http://www.youtube.com/watch?v=gWJFzAMsIlc
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aaron_sK
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PostPosted: Mon Mar 28, 2016 4:05 pm    Post subject: Reply with quote

Yes, I am bumping a three year old thread. Why? Because new testing data!

This is the victim: a two-speed electric fan from a '94 or '95 V8 Mustang. Very similar to the ever-popular Taurus or Lincoln fans that all the kids like.



This is the test rig. My truck battery (engine off), an el-cheapo Harbor Freight 30 Amp digital fusebox tester, and an old inline fuseholder repurposed with alligator clips so I can use the tester inline and break it but good!



BTW, I highly recommend that setup. Cheaper than a proper ammeter, but much more versatile than your average 10 amp multimeter test.

Unfortunatly there are no more pictures because holding my phone, the tester, and both leads on the battery while also keeping the fan from blowing itself away proved to be too much of a pain, so you'll have to trust my numbers here:

Low-speed startup: 22~24 amps
Low-speed running: 11.8-11.9 amps

High speed startup: Off scale high (30 amp meter)
High speed running: 27-ish amps
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chevymad
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Joined: 11 Jan 2004
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1987 Pontiac Formula

PostPosted: Mon Mar 28, 2016 4:33 pm    Post subject: Reply with quote

I've got the snap-on version of that ammeter. Think it goes to 40 or 50amps though and has adapters for different fuses. As you say, can be very handy.
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