Mechanical fan Vs Eletrical Fan For cooling system - PeachParts Mercedes-Benz Forum

Actros617 · #1 10-05-2008, 02:10 PM

I saw a eletrical cooling fan and it says it gives better mpg,power and cools much more than a the mechanical fan, but the size of the looks kind of small (covers 75% of the radiator), anyways which is better Eletrical Or mechanical Fan???

bustedbenz · #2 10-05-2008, 02:14 PM

Quote:

Originally Posted by Actros617

I saw a eletrical cooling fan and it says it gives better mpg,power and cools much more than a the mechanical fan, but the size of the looks kind of small (covers 75% of the radiator), anyways which is better Eletrical Or mechanical Fan???

I'll be greatly in the minority here but I'm a very dedicated supporter of the mechanical fan. Speaking from my own Mercedes, at least, I've always seen more temperature problems arise from the failure of the mechanical fan clutch than I have seen from the failure of the electric fan (Which, therefore, indicates to me that the mechanical fan, when functioning, is the more valuable device). I can't imagine the mpg difference could be significant enough to merit the modification, and I can't personally see how a fan in FRONT of the radiator is going to provide as much cooling effect to the engine as the mechanical one behind the radiator right in front of the engine itself is going to be able to.

Actros617 · #3 10-05-2008, 02:18 PM

http://www.dieselgiant.com/diesel_parts_for_sale.htm#Electric_Fan_Retrofit_Kit

This is what i was talking about??? The price is OVER KILL But i can get or make one for the fraction of the price...

sixto · #4 10-05-2008, 02:31 PM

As a point of trivia, the 190E has an engine driven fan with electric clutch.

To busted's point, there's probably very complex thermodynamics involved in deciding whether a puller or pusher is more effective. I presume Actros means replacing the clutch fan with a puller. If they make electric fans with sufficient CFM to cool a GM big block, they probably make something powerful enough for a 617. The question is, is there enough radiator surface area to fit such a fan? The compromise would be to hang an MB fan on an electric motor

One thing you can try on a cool day is to run a test loop with and without the clutch fan, keeping an eye on the temp gauge. Should be safe in a 617 with a working aux fan for backup. Note mpg and 0-60mph differences to see how much benefit there is to an electric fan.

Sixto
87 300D

sixto · #5 10-05-2008, 02:32 PM

You can talk to Charmalu. I believe he trusts his new Metric Motors 617 to a puller.

Sixto
87 300D

Actros617 · #6 10-05-2008, 03:10 PM

My only concern about the eletrical fan is IF IT QUITS, than that spells TROUBLE.

Matt L · #7 10-05-2008, 03:17 PM

It also spells trouble if your fan clutch gives out.

bustedbenz · #8 10-05-2008, 03:27 PM

I realize that nobody can ever design a system for every possible worst-case scenario, nor does it make sense to be paranoid about them, but with that disclaimer here's food for thought:

The electric fan is not an accessory; if it replaces the mechanical fan then it becomes a required piece to keep the car moving down the road. When your alternator dies three hours away from home, you WILL become roadsided when the voltage gives out in the battery and your fan can't run any longer, whereas a mechanical fan will keep right on turning and allow you to keep driving with no ability to recharge until you either need to start the engine or run the headlights.

Just something to think about and bear in mind, it's one more thing that may potentially cause a few hours delay waiting for a tow at a bad time, that wouldn't HAVE to exist.

kerry · #9 10-05-2008, 03:51 PM

Had an electric fan on a 617 in a 409d. It couldn't handle the heat load on a long climb. Mechanical fan could.

CANDIDE · #10 10-05-2008, 04:34 PM

Quote:

Originally Posted by Actros617

I saw a eletrical cooling fan and it says it gives better mpg,power and cools much more than a the mechanical fan, but the size of the looks kind of small (covers 75% of the radiator), anyways which is better Eletrical Or mechanical Fan???

The problem with the electrical fans is: without a custom fan shroud assembly a large portion of the radiator surface is not used by the fans.

I have 2 electric fans on my 300sdl and I will have a custom shroud built when I finnish my front end rebuild. Without the custom shroud, it cools ok. But, with winter coming, its a low priority for a few months.

Jeremy5848 · #11 10-05-2008, 05:28 PM

As Busted has implied, one of the advantages of a diesel is its ability to keep moving in spite of a charging system failure. Replacing the mechanical fan with an electrical one negates that advantage.

It's also worth remembering that the mechanical and electrical fans serve as backups for each other (even though not really designed to do that). Should the mechanical clutch fail in such a way as to disable the fan completely (does that ever really happen?), the electrical fan will operate when the coolant temp gets high enough. If on the road in a remote area, one could always hot-wire the electric to stay on all the time. That would provide enough cooling to get you back to civilization.

Deni · #12 10-05-2008, 06:34 PM

What sort of cfm does the mechanical fan flow at ~4000-4500 rpm? Can that flow be matched from an electrical fan so that maximum cooling can be had from idle?

If I'd start worrying that I'd get stuck in the middle of the desert light years from civilization I wouldn't go there in the first place.

sixto · #13 10-05-2008, 06:53 PM

Quote:

Originally Posted by Deni

If I'd start worrying that I'd get stuck in the middle of the desert light years from civilization I wouldn't go there in the first place.

Amen!

Sixto
87 300D

#14 10-05-2008, 10:00 PM

Quote:

Originally Posted by Actros617

I saw a electrical cooling fan and it says it gives better mpg,power and cools much more than a the mechanical fan

All three of those claims are false.
The mechanical fan is clutched so it does not consume much power when free wheeling. The only time its locked is when the engine is above 90*c. The electric fan still loads the engine by loading the alternator when its on.

If you are not overheating then the mechanical fan does not consume significant power, replacing it will not return anything but psychological gains and what minimal amount of fuel it does save will never be enough to cover the cost of the fan conversion. Gaining 1hp is not worth blowing $350!

At highway speeds the fan airflow pales in comparison to the natural airflow through the radiator caused by the vehicle moving, thats why MB limits the fan speed to 3500rpm. Above that RPM you'll be doing in excess of 75mph and the fan could never keep up with natural airflow let alone exceed it.

The only time an electric fan would have an advantage over the mechanical is at slow city or traffic jam speeds. In that case you would still be much better off upgrading the front electric fan and adding a temperature switch to its circuit.

If you want a worthwhile upgrade to the stock 5-blade aluminum fan, swap in the smaller waterpump pulley and 9-blade plastic fan from an 84-85 model. The plastic fan has less mass and moves more air and the smaller pulley (0.9:1 instead of 1.09:1) moves more water, both combined make for much better cooling performance. (Bo NOT use the smaller pulley with the aluminum fan or you could end up with fan failure and blade holes in your hood!)

kerry · #15 10-05-2008, 10:28 PM

Quote:

Originally Posted by ForcedInduction

you could end up with fan failure and blade holes in your hood!)

I had a fan blade break off on a 68 Landcruiser FJ 55 when I was driving about 55 mph. It was a dramatic event. The whole vehicle began shaking. I thought I had thrown a rod. Upon inspection, the blade had cut up thru the radiator and tank, and straight thru the hood, where it had launched to sites unknown. It was flying so fast I did not see it as it exited the hood despite the fact that I was looking directly at it. If my head had been bent over the motor when it happened it would have been a quick and easy end.