07-21-2008, 11:35 PM
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Join Date: Jan 2007
Location: Denver Co
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Is switching to an electric fan worth it?
I saw this on Centerline - is it worth doing? Centerline Products: FT645 12-Inch Electric Cooling Fan Kit
My current fan has a blade thats missing a small chunk, thought I'd replace the blade, but if there are cooling and power benefits to going electric... Well that makes sense to me??
Jeff |
07-22-2008, 12:58 AM
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Slacker
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Join Date: Mar 2006
Location: Northern NY, USA
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The power benifits would be neglidgeable, or at least not really worth the extra cost unless you are going for every modicum of power you can squeeze out (in which case, start by ditching carpeting, door liners, passenger seat, spare tire, big wet cell battery, jack, tools, and anything else that adds weight so you can get the free HP boost of a better power to weight ratio before spending money to make more  )
Not to say they don't give a small power boost, just that it's so insignificant in the grander scheme of things it's hardly worth doing for that reason alone.
The cooling advantage can be a gray area with as many people reporting better cooling with electrics as those that say the cooling got worse. (a good US spec mechanical fan with a good shroud can cool just as effectivly IMO)
The one thing you can say about them though: they are dead quiet until they turn in as opposed to the mechanical fan that makes noise all the time.
Things to also consider, mech vs electric:
Blow a fuse? Electric fan quits
Improperly set or failed temp sensor? Electric fan quits
Wire comes loose? electric fan quits
Charging system weak? Electric fan helps kill it more when the fan kicks on
Corrosion in the bushes, brushes or motor in general? Slow spinning to high draw to non-spinning at all electric fan
**
Break the belt? Mech fan quits (and charging system, and water pump)
Belt comes loose? Fan slows down losing effectiveness (and charging system, and water pump)
Imbalanced blades? Mech fan will eventually tear up the water pump bushing
Break a blade? Either will likely still turn, but the imbalance can cause issues.
EG: mech fan loses a blade, it'll eventually damage the water pump bushing, and may stuff the bit of blade through the shroud or radiator. Electric fan loses a blade, it'll effect the radiator in time ('cause that's what aftermarket ones are mounted directly to) and may stuff the bit of blade through the radiator. |
07-22-2008, 01:00 AM
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Alfa fans do explode for a few different reasons, sometimes taking out the radiator and denting the hood from inside. They also require engine power to drive them, and some complain of the noise. The electric fan is operated by a thermostatic switch, with an over ride if desired. They don't explode. With the car running, they are a little quieter than the pump driven fan. They don't take power from the engine to run them as they are usually off at speed. Being electric rather than mechanical, they can fail. However, as you are probably aware, most new cars use electric fans either in combination with a mechanical fan or as a stand alone system. Many racers use these as they do not operate at speed when air movement is enough for cooling. The choice is yours.
I would strongly suggest you do not continue to use your car with a damaged fan.
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 Gordon Raymond
Illinois SNO Chapter DIRECTOR 
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07-22-2008, 05:10 AM
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My fan exploded last week and put a big hole in the radiator  Like Darren and Gordon said... don't risk driving the car with a damaged Fan. |
07-22-2008, 06:03 AM
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the reason most engines use electric fans now isnt because of increased eficency, it is because it would be hard to route fan belts aroound the corner on sideways mounted engines. the electric fan still pulls engine power in the form of increased load on the alternator. it still takes the same amount of power to turn a fan, whether by belt or electric motor.
cliff
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07-22-2008, 06:10 AM
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In the Spiders' nest...
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Join Date: Jun 2005
Location: Nutley/NJ & Middletown/OH, USA
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 Quote:
Originally Posted by sgtpeper
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I wrote a post about my experience with the electric fan. You can see it by clicking here.
Best regards,
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Enrique
Spider 74, 84 & 87
164 93L & 95Q
Milano 88 Verde
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07-22-2008, 06:31 AM
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Years ago I installed an electric fan in a 87 Spider. I went the shade tree mechanic route and set it up as a pusher with black nylon ties. I did notice in the summer the car ran a lot hotter in traffic then I was comfortable with. I personally do not think it is really worth it and have not done it to my current cars.
Tom
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07-22-2008, 10:18 AM
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Quote:
Originally Posted by sgtpeper
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1) 5-7 hp boost.
2) You get better cooling when you need it the most, i.e. when the car is idling or sitting in traffic. That's when the mechanical fan is turning the slowest. When you're at speed, generally the electric fan isn't needed, so you get a power boost when you need it.
3) If you mount it in front of the radiator, you get a much more open engine compartment. On a Spica car, you can now replace a water pump without touching the fan, radiator, etc.
My .02,
bs
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07-22-2008, 10:20 AM
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Quote:
Originally Posted by Alfacliff
the reason most engines use electric fans now isnt because of increased eficency, it is because it would be hard to route fan belts aroound the corner on sideways mounted engines. the electric fan still pulls engine power in the form of increased load on the alternator. it still takes the same amount of power to turn a fan, whether by belt or electric motor.
cliff
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The electric fan will still give you some benefit, as it's generally not turning when the car is moving at speed. It does most of it's work when you're idling, or sitting in traffic, at those speeds hp doesn't really matter.
bs
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07-22-2008, 10:22 AM
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Weird you seem to be the only one who really believes in this mod.
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07-22-2008, 10:24 AM
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to move a specific amount of air against a specific back pressure requires the same hp regardless of power source. the efficency of the fan blades is in the formula tho. but to claim 5 hp for a fan driven by the belt, and nearly none by an electric fan doing the same work is not right. also, the airflow through the radiator at speed would reduce the power required to turn the fan, whether electric or belt driven. most of the electric fans have no shroud, so should not be as good at cooling the radiator as a fan with a shroud.
cliff
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07-22-2008, 10:41 AM
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I haven't done this mod yet but I want to. Yes, I realize that there are risks but they can be mitigated by a competent installation. A few questions for those who've done this:
1. Push or pull? I'm leaning towards a pusher (I no longer have A/C)...any issues?
2. Shroud or not? Any gain/loss from ditching the shroud with a pusher fan?
3. Thermostat location...in/on radiator of course, but which part? up by top hose or down by lower hose?
4. On/off temps?
5. Manual on/off control with a separate relay as a backup to the thermostat. Good idea?
Lastly,
6. What CFMs are required--for 12" fans, I've seen anywhere from 1100-1400 listed? What are you guys running?
TIA for a good thread,
Paul
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Paul
'86 Spider Graduate
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07-22-2008, 11:01 AM
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Quote:
Originally Posted by sgtpeper
Weird you seem to be the only one who really believes in this mod.
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There was somebody back in the 70's that dyno'd a bunch of common mods for the time, that's where the 5-7 hp number comes from. I didn't make that one up. Is that number lower with some air flow over the front of the motor? Probably.
Does an electric fan draw 5-7 hp from the motor? I'd argue that on a couple of points. First, the electric fan doesn't generally come on when you're at speed, if it's not on it's not draining hp. Second, when the electric fan *is* on, it can draw from stored power (battery), not purely from the alternator.
I do know one person who did not like the electric fan when it was installed as a pusher, felt the engine ran a little warmer than normal that way. Aside from that, I know quite a few people that have installed electric fans, and aside from the one, all are happy.
Alfa did away with mechanical fans in the Alfettas, no?
bs
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07-22-2008, 11:16 AM
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Quote:
Originally Posted by BattleBug
I haven't done this mod yet but I want to. Yes, I realize that there are risks but they can be mitigated by a competent installation. A few questions for those who've done this:
1. Push or pull? I'm leaning towards a pusher (I no longer have A/C)...any issues?
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Quote:
Originally Posted by BattleBug
2. Shroud or not? Any gain/loss from ditching the shroud with a pusher fan?
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Imo, you absolutely need a shroud.
Quote:
Originally Posted by BattleBug
3. Thermostat location...in/on radiator of course, but which part? up by top hose or down by lower hose?
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At the bottom. If you look at your Spider, in the sheet metal at the bottom of the radiator, on the drivers side, you'll see a little half moon sized recession. That's a perfect spot to install a bung and thermo switch in the radiator.
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'84 manufacture ~ '85 MY Spider Graduate 
