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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Mon Aug 12, 2013 9:09 pm Post subject: |
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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? _________________ A redline a day keeps the carbon away! |
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aaron_sK Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Mon Aug 12, 2013 9:17 pm Post subject: |
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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. |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Mon Aug 12, 2013 9:21 pm Post subject: |
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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. _________________ A redline a day keeps the carbon away! |
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QwkTrip 11sec Club
Joined: 17 Feb 2004 Posts: 3942 Location: Peoria, IL
1989 Pontiac Firebird
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Posted: Mon Aug 12, 2013 9:24 pm Post subject: |
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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 11sec Club
Joined: 17 Feb 2004 Posts: 3942 Location: Peoria, IL
1989 Pontiac Firebird
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Posted: Mon Aug 12, 2013 9:35 pm Post subject: |
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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 Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Tue Aug 13, 2013 7:39 pm Post subject: |
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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!
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. |
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Alphius Peanut
Joined: 05 Sep 2006 Posts: 2429 Location: Grand Mound
1984 Chevrolet Camaro Z/28
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Posted: Tue Aug 13, 2013 9:35 pm Post subject: |
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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. _________________ 84 Camaro Z28 - LS1/T56
85 Silverado - Low and Slow |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Tue Aug 13, 2013 10:54 pm Post subject: |
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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. _________________ A redline a day keeps the carbon away! |
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91RSVert Member
Joined: 16 May 2007 Posts: 2736 Location: AR
1991 Chevrolet Camaro RS
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Posted: Fri Aug 16, 2013 2:13 pm Post subject: |
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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. _________________ 2008 GMC Z71
1991 Camaro RS Vert
1972 Jimmy 4x4
20ft Longhorn Car Hauler
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Alphius Peanut
Joined: 05 Sep 2006 Posts: 2429 Location: Grand Mound
1984 Chevrolet Camaro Z/28
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Posted: Fri Aug 16, 2013 2:37 pm Post subject: |
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My dual IROC fans draw well over 30amps for a second or two under startup load. _________________ 84 Camaro Z28 - LS1/T56
85 Silverado - Low and Slow |
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aaron_sK Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Fri Aug 16, 2013 4:01 pm Post subject: |
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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 Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Mon Mar 28, 2016 4:05 pm Post subject: |
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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 Master B
Joined: 11 Jan 2004 Posts: 5474
1987 Pontiac Formula
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Posted: Mon Mar 28, 2016 4:33 pm Post subject: |
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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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