Originally posted by nrubenstein
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Why you should convert to an electric fan
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Thats a good point on the thermoswtich. I think it is also important to use a thermo switch with some hysteresis built in, so the fan isn't switching on and off constantly.
Years ago I built an electronic controller for my thermo fan conversion, was an electronic kit you could buy at Jaycar in Australia. It had a set point, and then you could set the hysteresis, so you could get it to come on at say 90degC, then turn off again when it got to 85degC or whatever. worked pretty good, never came on when cruising and only every now and then when stuck in traffic. I installed an override switch in the cabin so that i could force the fan on if required.Last edited by e30davie; 05-02-2017, 02:46 PM.
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it’s worth noting that hp is an rpm^3 function. in that video it was a low rpm engine 6000rpm only, and the pulley ratio looked about 1:1.
On the m20 even if the fan is 2” smaller diameter the water pump runs somewhat faster than the crankshaft and if you are turning the engine 7000rpm it is going to consume quite some hp. The difference between 7000 and 6000 is more than 50%
There is also a difference between warm/hot engine and a hot engine with the fan "fully" engaged as it is the rpm of the actual blades that matter.
you can feel the throttle response change and hear the additional noise when the OE clutch grabs, i try run my engine colder the stock and my fan takes quite a while to kick in and many times it doesn't engage 100% unless its really hot and im stuck in traffic for extended periods so under normal conditions it wouldn’t be causing that much parasitic loss to be worried about but it does have an effect.
As for electric at the end of the day you need to cool the engine in the worst conditions for me would be 115F sitting in heavy traffic with A/C .
I’ve thought about an electric fan to replace the clutch with aux fan kept OE but the stock system has worked well for me so far if parts are in good condition but with a robust parts and control there are certainly advantages with electric.
Maybe those who have done an electric fan can share their control strategy?
For the retrofitted electric fan do you run the electric fan at single speed or multi speed and under what conditions does it turn on, its on while engine is running, or is it a temp based thing?
for the aux fan what did you do?
- Aux fan 100% as is
- Aux fan as is but replace the temp switch with the lower temp switch
- Deleted aux fan
etc
etc89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...
new build thread http://www.r3vlimited.com/board/showthread.php?t=317505
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Originally posted by nando View Postthat's pretty silly. Most modern cars use a fan controller and no mechanical fan. Usually if they fail, the fan goes full tilt so you know something's wrong. I can't say I've heard of very many electric fan failures, if any at all. And mechanical fans definitely do fail.
Modern cars from the factory, yes, but when it comes to retrofitting an electric fan onto many older cars you have limited options of questionable quality. I am only familiar with systems utilizing a probe that fits in the radiator fins, or the Spal programmable units, neither of which work reliably from my own experience.sigpic
1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN
WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack
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Originally posted by e30davie View PostYears ago I built an electronic controller for my thermo fan conversion, was an electronic kit you could buy at Jaycar in Australia. It had a set point, and then you could set the hysteresis, so you could get it to come on at say 90degC, then turn off again when it got to 85degC or whatever. worked pretty good, never came on when cruising and only every now and then when stuck in traffic. I installed an override switch in the cabin so that i could force the fan on if required.
That is exactly how the Spal programmable controller is supposed to work, when it functions properly. I had one in a high comp 4AG AE86 and it was not trustworthy.sigpic
1991 325i Sport - Calypsorot Metallic - DAILY DRIVEN
WTB in SoCal: 8"/10" Lukebox, leather Sport steering wheel, 60L MotoMeter fuel gauge, Thule/Yakima roof rack
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Originally posted by 5Toes View PostI dont run a fan at all on my m42. The car runs prime, temp only creeps up in traffic after 10mins. lucky for me there is never ever traffic where I travel...
I might try this on my m42. Saving weight is a bonus also.
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Originally posted by Victell View PostHmmteresting. What are the high ambient temperatures where you live, or when in traffic?
I might try this on my m42. Saving weight is a bonus also.
While you can get away with running no fan on a track car, it's an awful idea on a street car. Just imagine if you get stuck behind a crash that reduces a highway to one lane with no exit before the crash, you'll have to creep forward to not lose your space like everyone else, and you'll likely overheat.
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Originally posted by roguetoaster View PostWhile you can get away with running no fan on a track car, it's an awful idea on a street car. Just imagine if you get stuck behind a crash that reduces a highway to one lane with no exit before the crash, you'll have to creep forward to not lose your space like everyone else, and you'll likely overheat.Originally posted by Matt-Bhey does anyone know anyone who gets upset and makes electronics?
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Originally posted by Vincent Brick View PostThat is exactly how the Spal programmable controller is supposed to work, when it functions properly. I had one in a high comp 4AG AE86 and it was not trustworthy.
Mine was pretty reliable, good couple of years of service. I just used a cheap electric fan without a shroud, if i did it again id just get an oem fan off some FWD car at the wreckers that have a shroud built in.
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Originally posted by Vincent Brick View PostModern cars from the factory, yes, but when it comes to retrofitting an electric fan onto many older cars you have limited options of questionable quality. I am only familiar with systems utilizing a probe that fits in the radiator fins, or the Spal programmable units, neither of which work reliably from my own experience.
The only difference in the newer BMWs is the sensor is in a radiator hose connection but it's on the same side of the radiator in basically the same position. They use a PWM controller instead of a switch, but what that really gives you is smoother operation (rather than on/off or two speeds with the E30 fan).
The concerns with leaking coolant are equally silly - if your car is leaking enough coolant to leave the thermoswitch exposed to air, then fix your damn coolant leak. lol.
George - I always thought using a manual switch for the fan was hacky and prone to failure. Use a thermoswitch or a PWM controller. You could just as easily forget to turn the thing on, which I've heard of happening too.
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lol i just replaced my fan clutch and fan blade, just because it was only like $110 for the clutch and blade, will move way more air than any electric fan for even close to the same price, it simply works, when the air coming through the rad gets hot, it locks up and pulls more air, when its not, it spins slowly and circulates a little air through the engine bay, which i personally dont have an issue with,
However, on my tii thats a different story, that thing is bolted straight to the water pump pulley, always pulling air all the time, that is definitely a good candidate for an electric fan.
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The other thing to consider is the "fail on" that most oem electric fans have, Id have to have a think about how that looks electrically, but i suspect its a normally closed relay. Having said that mine was always normally off, never had an issue. I am a paranoid coolant temp watcher though, so i would have caught the temp going up long before any dramas. If the wife drove the car it would be another story. which is why OEMs make them fail on....
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