..what if? ..

[Ecc0]

..most of the cars i have had, were with mechanically attached fan to crankshaft so its always cooling down engine regardless engine temperature, and i found that rather good, safe and VERY reliable approach...my E85 had aluminum cast block and fan was electrical. I must say that car never ever had any problem with electrical fan or with temperature..rock solid, really..but i always felt a bit 'non secured'..I was hoping to see cooling fan attached to crankshaft of my S54 engine on my Coupe, because i thought it will be natural to have due iron cast engine block..but unfortunatelly, its electrical fan too..sigh..so, what if electrical fan fail to work, and in the middle of nowhere?? Engine will go bye bye or what?? Anyone had any experience with this ??

 

[astroboy]

1. Fan attached to crank too has a clutch which activates the fan when cooling needed. If that clutch fail to engage, engine still overheats.

2. Most folks convert crank fan to electric fan due to few reasons and never the other way round.

Benefit of running electric fan:
1. It spins at higher speed than the crank, hence more effective in cooling.
2. Electric fan is quieter and only spins when necessary
3. The combustion engine is relieved from the fan load, hence engine output is more focus to drive the wheels of the car rather than other ancillary functions. More "usable" horsepower and better fuel efficiency.

 

[Ecc0]

1. Fan attached to crank too has a clutch which activates the fan when cooling needed. If that clutch fail to engage, engine still overheats.

2. Most folks convert crank fan to electric fan due to few reasons and never the other way round.

Benefit of running electric fan:
1. It spins at higher speed than the crank, hence more effective in cooling.
2. Electric fan is quieter and only spins when necessary
3. The combustion engine is relieved from the fan load, hence engine output is more focus to drive the wheels of the car rather than other ancillary functions. More "usable" horsepower and better fuel efficiency.

..mm..im not sure about (1), because I see fan spinning in my RR all the time, ill check it...but most important, im wondering how critical is electrical fan failure during car motion ??

 

[astroboy]

You notice the crank fan spinning all the time because it's passive spinning due to the motion created by the internal shaft, u can actually use your hand to stop the fan, if the clutch didn't engage [I think only, DON'T TRY!! Dowan u to lose your fingers!] :4:

Another method u can try is try spinning the fan with engine OFF. If the fan spins, then there's a clutch. Try it out! :4:

That's a heat sensitive clutch and not controlled by any wire or electrical pulse. It kind of have a brain of its own.. :24:

RR Fan clutch:

 

[Ecc0]

..mm..yes, its looking exactly as it is on your pic (surface fan is attached on to)..mmm

 

[jarance]

You notice the crank fan spinning all the time because it's passive spinning due to the motion created by the internal shaft, u can actually use your hand to stop the fan, if the clutch didn't engage [I think only, DON'T TRY!! Dowan u to lose your fingers!] :4:

Another method u can try is try spinning the fan with engine OFF. If the fan spins, then there's a clutch. Try it out! :4:

That's a heat sensitive clutch and not controlled by any wire or electrical pulse. It kind of have a brain of its own.. :24:

RR Fan clutch:

It is control by a bi-metallic strip in a setup called fluid coupling.
The bimetallic strip consist of 2 metal which expand at different length for the same amount of change in temperature.
This will cause to bi-metallic strip to bend and push a rod and will adjust the amount of oil in the clutch fan.
By adjusting the oil, the speed of the fan will changed. i.e. the hotter the air thru the radiator, the faster the fan will
spinned but not faster than the engine rpm.

 

[Ecc0]

..i see..but in case of my Z, its entirely electrical, so in case electrical fan fail because of any reason, is it air flow itself enough to keep engine in 'safe zone' until reach destination/garage or anything, considering its driven normally and not in any racing mode or high rpm??

 

[astroboy]

It should... but to find such ideal traffic and weather situation is like striking lottery because the moment you slow down, your temperature will shoot through the roof.

Stop at the road side, open hood and let it air cool, then continue journey until it heats up.. then repeat the "pit stop"... on down hill, engage neutral and kill the engine.. :4: I tried that before, fan belt snapped due to alternator seizure. Hence water pump fail and it happened during peak hour in Kota Raya, I had to stop at every other bus stop to let the engine cool down, then drive by closely monitoring the temperature gauge on my E36 318i manual, limping my way to Jalan Ipoh. The few km journey took me almost an hour.. :4:

 

[t2ribena]

most electric fan does not dies off suddenly...normally it makes some grinding sound or the fan slows down and not able to achieve high rpm...for ppl who is passionate about their cars, it will be noticeable when then fan is going kaputs....coz every detail also you wan to know...hehehehe

 

[Ecc0]

..mmm..so at the end of the story, good old way of sticking it to the crankshaft is way more better and reliable...why they didnt do it on M cars, im wondering..

 

[bmwky]

Well IMO, electrical fans are more reliable, either it works or it doesn't. When it fails, it's very easy to find out, you temp will shot up very fast. Most of the time electrical fan fails due to the temperature switch/relay malfunction.

BMW didn't put a viscous clutch fan on their M cars probably due to the owners's "fear" that it may rob some HP off the engine.

 

[t2ribena]

to reduce the parasitic drag thus allowing the engine to churns out more power and increase the engine efficiency...

now with the efficient dynamics thingy...they even 'cut-off' the alternator charging circuit to the battery when you put your foot on the accelerator pedal and activates this charging circuit only when you off pedal or brake...that's the brake energy regeneration in the current ED cars...

the 'mechanical' fan can also fail as there is a fluid coupling clutch like astroboy says...its part of wear and tear...i think its more towards your psychology confidence on how this should work and not...but the truth is otherwise...i have seen failing clutches as many as electrical fan failure...

 

[Ecc0]

..im wondering is there any conversion kit available for electric->clutch fan , available..less control spots system has, more reliable is...my father had Mercedes W126, and that thing has fan fixed directly on to crankshaft, if im not mistaken..without any clutch or anything..and there is nothing to fail in such system...claim for more power sounds very weak to me, because plain physics says that for same air mass flow you have to have more energy wasted by engine to power electric fan+resistance in wiring(minor, but exists) and electronic systems need to monitor it, than raw fan attached straight to engine, pushing same airflow..if calculation is based on fact that electrical one turning on/off then yes, it uses less energy IN TOTAL..but when its running and it will, it will 'choke' engine more than mechanical one..simple as it is..and its far less safe than mechanical one...so im wondering still..whyyyyyyyyyy..

 

[t2ribena]

double posting......

 

[jarance]

My M54 engine have a clutch fan and a electrical pusher fan.

I once had an accident where the radiator was slight push in and prevent the clutch from turning
but the electric fan can still work.

Experienced the temperature rises to about 3/4 mark when at stationary but dropped back to normal (1/2 mark)
when the car is moving again.

Not a good experience to see the temperature going up and down while driving to the workshop.

 

[aidilj]

It should... but to find such ideal traffic and weather situation is like striking lottery because the moment you slow down, your temperature will shoot through the roof.

Stop at the road side, open hood and let it air cool, then continue journey until it heats up.. then repeat the "pit stop"... on down hill, engage neutral and kill the engine.. :4: I tried that before, fan belt snapped due to alternator seizure. Hence water pump fail and it happened during peak hour in Kota Raya, I had to stop at every other bus stop to let the engine cool down, then drive by closely monitoring the temperature gauge on my E36 318i manual, limping my way to Jalan Ipoh. The few km journey took me almost an hour.. :4:

Just a small point but turning off engine while coasting is not a great idea, you might use up all brake boost assist then the car would be hard to stop.

 

[ALBundy]

Ecco, are you sure your Z4M comes with an electric fan instead of a fan clutch?? As far as I know all S54 engines come equipped with a fan clutch, well mine does have a fan clutch! I just check on realoem.com to reaffirm, and Z4M is using a fan clutch. In the S54 engine, just like traditional ones there are 2 fans. One is a mechanical viscous fan or popularly known as a fan clutch and the other is the electric fan which is mounted in front of the air cond condenser.

On the M54 (double vanos), there is only ONE electric fan, mounted directly behind the radiator. For those that want to convert from fan clutch to electric fan, this is the fan to get. OEM ones about 1300-1500.

Jarance, yours could be a M52TU. M54 comes with only one electric fan as stated above. That's one of the difference between M52TU and M54.
Some milestones on the M5X engines,

M50 - Mother of all (e34, e36)
M50 TU - Single Vanos
M52 - Aluminium block (started in E36 328)
M52 TU - throttle by cable, double vanos (e46, e39)
M54 - Electric fan

 

[astroboy]

W126 fan clutch:

BMW S54:

BMW M54:

U still need an electric fan for the aircond though..

 

[t2ribena]

care to elaborate more on the losses you are referring to on the electrical energy used to power the fan vs the mechanical loss that you claim that it has lesser energy loss?

as mentioned earlier, parasitic drag from viscous coupled mechanical fan contributed to loss of energy, like all viscous coupling system, the system is not 100% efficient due to the slippage or partial engagement of the coupling...electric fan does not have this loss as it is a direct drive system...

apart from the parasitic drag on viscous coupled mechanical fan, the drag created by each blade in order to push/displaces the air creates significant 'unwanted' load on the engine...as the density of the air increases as the blade pushes it at higher speed, in this case as you rev your engine higher, the factor of the drag increases exponentially...to avoid this that is why the engineers opt for the electric fan, yes it loads but on the electrical circuit whereby when a higher rating alternator is used, this does not directly loads on the engine...in electrical system when you have sufficient current in the supply system, and the loads are within this supply current limits, you are not creating any loss of power to other circuit powering for example the spark systems and etc...

..im wondering is there any conversion kit available for electric->clutch fan , available..less control spots system has, more reliable is...my father had Mercedes W126, and that thing has fan fixed directly on to crankshaft, if im not mistaken..without any clutch or anything..and there is nothing to fail in such system...claim for more power sounds very weak to me, because plain physics says that for same air mass flow you have to have more energy wasted by engine to power electric fan+resistance in wiring(minor, but exists) and electronic systems need to monitor it, than raw fan attached straight to engine, pushing same airflow..if calculation is based on fact that electrical one turning on/off then yes, it uses less energy IN TOTAL..but when its running and it will, it will 'choke' engine more than mechanical one..simple as it is..and its far less safe than mechanical one...so im wondering still..whyyyyyyyyyy..

 

[aidilj]

Ecc0, by going electric the function of the fan can be controlled by software rather than temperature alone - set inside the mechanical clutch. In development, instead of changing a component to modify fan turning ON threshold they can just change the software.

And instead of just turning on or off, the electric fan be varied in speed. Means only use power as much as it needs to. And as it is controlled electronically, it can be turned off anytime when you need more power somewhere else.