The Myth Of The Electric Fan

[rick540]

8th radiator, holy cow Rick, are you saying I should budget for a new one every second year?

Nah, you should be fine for a while seeing as I replaced virtually the entire cooling system with new parts and filled it with the correct mixture of genuine BMW coolant.

It's when guys put in plain water, or neglect a leak etc that stuff happens.

 

[frikkieh]

So let me get this - MERC's actually have a motor and propellers to power the vehicle? :rollsmile:

I had to replace my electric fan that was failing intermittendly. This is not just a fan with an electric motor, it has an electronic circuit inside the fan assembly that rotation fires SCR's, connected to the magnetic coils that actually make the fan spin.
This is the BMW's version of electric fan speed control (which was re-designed BTW on the replacement unit)
Due to the design, I can believe that the viscus fan will indeed move more air.

 

[Fordkoppie]

The mechanical fan on the merc is a very clever piece of kit.
It has a clutch like the AC compressor. When activated by a thermo electric switch, it engages with a 100% lock until the system has cooled down.
When in that mode it sounds like the fan only can propel the car forward. lol

 

[moranor@axis]

merc also use the same kind of clutch to turn off the super charger :rollsmile:

 

[Sankekur]

merc also use the same kind of clutch to turn off the super charger :rollsmile:

Have heard of that, a pretty cool idea :grin:

 

[Phoenix]

After my 2nd radiator and expansion bottle as well as hoses and cowling etc. i did an electric fan conversion on my 325i.

I'm sure a few of the fanatics can remember my BMW Spilling it's cooling system on Zwartrkops a while back and then again 3 weeks later with the replacement tds fan from bmw.....

If you dice/race/play with your car get rid of the visco unit. This is ofcourse my personal R9k later no labour included opinion. i personally preferred the Visco unit until it declared war on my wallet.

The electric conversion however is not simple and you will need a different thermostat, fan switch and atleast 1 if not 2 high volume fans.

Like i said, this is my personal opinion and i do push my car pretty hard.

 

[bimmer330]

i think a lot of enthusiasts make one common erroneous assumption.. and that is that the engineer that originaly designed the intake/exhaust/cooling/whatever system did not know what he was doing..

ok, so obviously they have design parameters that they have to meet, weight,cost ect. but thinking you can modify a system for the better without understanding why it was designed in a certain way originaly is a bit silly..

after researching the viscous vs. electric fan some time ago i also discovered the vast amounts of air moved by a viscous fan , and decided to not to replace them with electrics on my remapped diesels, which already suffers from a higher heatload than the cooling system was designed for..

just my 2c ..

South Africa also suffer from high temperatures sometimes and the electric fans do work harder here then in Europe.

 

[BAD328iT]

"This article makes no claims as to it's validity when applied to other vehicles. I get a lot of angry email from various automotive forums where this article is posted saying how wrong I am, yet every one of those people seem to miss the fact that this article is specific to the 2nd gen ('86-'92) RX-7. "


Did everyone miss that part of the huge article? Sure it is a fact that electric fans will not move the same aount of air as a mech one of the same scope but the statement of a higher load on the alternator? the alternator has a fixed amount of drag on the system, even if you get a bigger altenator the amount of rotational strain exstra will be very minimal but if you put a fan assembly on, it is alot more drag as it is alot more weight. rotating over much wider radius. Also the alternator does not create more drag with more strain, it has a fixed output no matter what the elec usage of the car is, if it is not adiquate you may start losing saprk, and can ealily be fixed buy fitting a bigger altenator that wont add as much drag on the crank as the fan.

elec ftw

 

[rick540]

the alternator has a fixed amount of drag on the system,

No it does not have fixed drag. The drag is relative to the load on the electrical system.

 

[zaleonardz]

Or just move to Alaska, cooling issue solved

 

[whattingh]

the alternator has a fixed amount of drag on the system,

No it does not have fixed drag. The drag is relative to the load on the electrical system.

+1

 

[freerider]

Ill just stick to my electric fan thank you very much. On the interwebs we will find just about everything to justify anything.

 

[Fordkoppie]

Ill just stick to my electric fan thank you very much. On the interwebs we will find just about everything to justify anything.

+1
And no one seems to worry about their alternators when fitting silly speakerboxes and amps. Oooh noooo - anything but an electric fan :slap:

 

[zaleonardz]

Including Steve Hoffmeyer ?

Ill just stick to my electric fan thank you very much. On the interwebs we will find just about everything to justify anything.

 

[freerider]

Ill just stick to my electric fan thank you very much. On the interwebs we will find just about everything to justify anything.

+1
And no one seems to worry about their alternators when fitting silly speakerboxes and amps. Oooh noooo - anything but an electric fan :slap:

I have a 16inch unit, when it comes on you cant notice any dimming of dash lights etc. Ive been in many a car where every bass beat has the dash lights dimming like crazy.

Including Steve Hoffmeyer ?

Ill just stick to my electric fan thank you very much. On the interwebs we will find just about everything to justify anything.

Well, almost everything...

 

[tarintino]

What I didn’t read in the write up posted is any reference to inertia - Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion.

Inertia is a constant that the engine will have to overcome in order to spin the fan blades and keep them spinning even more so when it reaches temperature and locks, as the fan blades are now rotating directly with the engine more force is required to rotate the blades and that force increases the faster you go (higher engine rev’s) so surely if an electric fan is used horse power is increased higher in the rev range as the engine doesn’t have to use energy to push the viscous fan.

Of course I'm only accounting for when the fan is in the locked position, when in the "free" position inertia is almost nonexistent so I don’t believe that the electric fan would be better than the viscous fan in this scenario.

The biggest gains would be on those nasty Toyota’s with the fans that spin in unison with the engine.
:rollsmile::rollsmile:

 

[freerider]

Even in the so called free position, hold a viscous fan but the nut and turn the blades. There is still a considerable amount of resistance present.

 

[Nic_s]

Electric and viscous each has plus and minus points as talked about in the article.

Viscous can be very noisy and when fully engaged it will take away some HP. Personally I've never even noticed the viscous in my 318i, but the 540 is another matter where the viscous is quite loud.

Electric is quite more of the time, but it is less efficient and moves less air. There's no getting around that.

If the electric works 100% fine for you, then I say go for it. I'm thinking of doing it with my 540 as I'm tired of the vacuum under the bonnet, but I will add another temp sensor because the one in the dash is electronically pegged and only shows that the car is overheating when it's to late.

At the end of the day the article should only be used as a guide. Neither is best as that will depend on the car/setup you have.