Electric fan Vs Viscous fan?

[Rich_325_sport]

Why do people change viscous fans for electric fans? what are the advantages/disadvantages.

I'm asking because i think the viscous fan on my sport has a dodgy clutch (not physically checked it yet) as it gets hot in traffic (didn't used to) and i've changed thermostat, radiator, and coolant recently. As i am looking at the fan anyway, i thought i'd ask as i'd seen the mod before.

cheers

Rich

[Turbo-Brown]

Guess electric fans don't sap power all the time, which is nice, personally I prefer the mechanical ones though because fans do take quite a lot of power and in traffic I'm always scared of blowing a fuse or having the motor fail (just paranois though )

[e30_Turbo]

I'm looking at a RS turbo fan for my new project.....seen two on the 2.5 rad before, not sure on temp switch values tho...

And I so want rid of the truck noise when she gets hot.......must sap a few ponies then.....

[Karan]

I'm looking at a RS turbo fan for my new project.....seen two on the 2.5 rad before, not sure on temp switch values tho...

And I so want rid of the truck noise when she gets hot.......must sap a few ponies then.....

i have a dual circuit switch which can work at 80degc or 88degc..... depends how u wire it up.... mines wired to 88 at the moment and switches on just above half and brings temp down to exactly half

[e30_Turbo]

I'm looking at a RS turbo fan for my new project.....seen two on the 2.5 rad before, not sure on temp switch values tho...

And I so want rid of the truck noise when she gets hot.......must sap a few ponies then.....

i have a dual circuit switch which can work at 80degc or 88degc..... depends how u wire it up.... mines wired to 88 at the moment and switches on just above half and brings temp down to exactly half

I'd think the 80 would be better as I bet the lump gonna get real hot real quick......it does hit just over half now, will keep an eye on when turbo's on......may need to add these just in case.

[E30BeemerLad]

I mentioend this to my brother not long back as I was thinking about going the RS Turbo leccy fan route, thinking I would be saving myself a couple of BHP.

He said not to bother as the viscous will flow more air and stops working above 40mph.

He works for Lotus Engineering and spends his day running all manner of machinery on rolling roads doing emissions testing and general design consultancy work.

So I haven't bothered considering it since.

[hoshy]

I've heard good things about this. and there must be a reason manufacturers moved from viscous to electric... Usually it's cost but I'd imagine the electric setup is more expensive so it must be either better for bhp or more reliable. Either way I reckon it's a good plan.

[e30_Turbo]

I mentioend this to my brother not long back as I was thinking about going the RS Turbo leccy fan route, thinking I would be saving myself a couple of BHP.

He said not to bother as the viscous will flow more air and stops working above 40mph.

He works for Lotus Engineering and spends his day running all manner of machinery on rolling roads doing emissions testing and general design consultancy work.

So I haven't bothered considering it since.

Thing is, once it gets hot the joint will sieze up giving the fan it's power, so no matter what speed it'll still be powering the fan......not sure how he figures they stop after 40 tho.....never heard that before......

See if you can get his reasons for it....be interested to hear what he thinks.....

I'm going electric so I have contol over the system.........I may need to adjust the fan size and temp control soon.........

(the noise it makes is a big factor too )

[E30BeemerLad]

Carl - I have emailed my Bro and will let you know if he bothers to respond

cheers
lee

[e30_Turbo]

Carl - I have emailed my Bro and will let you know if he bothers to respond

cheers
lee

Who's Carl????

Mark.

[E30BeemerLad]

:yeahthat:

sorry mate - losing the plot!

[Brianmoooore]

[quote="hoshy"]I've heard good things about this. and there must be a reason manufacturers moved from viscous to electric... Usually it's cost but I'd imagine the electric setup is more expensive so it must be either better for bhp or more reliable. Either way I reckon it's a good plan.[/quote
Most manufactuers have moved from mechanical fans to electric, because they have their engines mounted sideways, and driving the wrong wheels.

[Brianmoooore]

I mentioend this to my brother not long back as I was thinking about going the RS Turbo leccy fan route, thinking I would be saving myself a couple of BHP.

He said not to bother as the viscous will flow more air and stops working above 40mph.
.

He's making a not unreasonable assumption that the fan moves the air through the rad at a certain speed, and at about 40MPH that speed is matched by the ram effect through the radiator. Hence the mechanical fan is doing no work, and consuming no energy, even if the viscous coupling is lock (which it probably won't be, as the ram effect will be providing more than enough cooling).
To provide the same amount of airflow as a mechanical fan, an electric fan will consume about twice as much power from your engine (via the altenator).

[e30_Turbo]

I mentioend this to my brother not long back as I was thinking about going the RS Turbo leccy fan route, thinking I would be saving myself a couple of BHP.

He said not to bother as the viscous will flow more air and stops working above 40mph.
.

He's making a not unreasonable assumption that the fan moves the air through the rad at a certain speed, and at about 40MPH that speed is matched by the ram effect through the radiator. Hence the mechanical fan is doing no work, and consuming no energy, even if the viscous coupling is lock (which it probably won't be, as the ram effect will be providing more than enough cooling).
To provide the same amount of airflow as a mechanical fan, an electric fan will consume about twice as much power from your engine (via the altenator).

Can't argue with that, top info

[E30BeemerLad]

yeah , me too, can't believe my brother, clever little fcuker! Oh and you too Brianmoore!

[Wilson]

I mentioend this to my brother not long back as I was thinking about going the RS Turbo leccy fan route, thinking I would be saving myself a couple of BHP.

He said not to bother as the viscous will flow more air and stops working above 40mph.
.

He's making a not unreasonable assumption that the fan moves the air through the rad at a certain speed, and at about 40MPH that speed is matched by the ram effect through the radiator. Hence the mechanical fan is doing no work, and consuming no energy, even if the viscous coupling is lock (which it probably won't be, as the ram effect will be providing more than enough cooling).
To provide the same amount of airflow as a mechanical fan, an electric fan will consume about twice as much power from your engine (via the altenator).

Bloody hell... that really makes sense!!!!

[Widge]

Yeah but when you're sitting in a traffic jam at idle the fan is only doing 900rpm when it's cooling efect is needed most. Manufactureers switched to leccy fans as they have more control, when you're sitting still at idle they can be going flat out disipating all the heat built up from just before you stopped. I'm gonna switch to leccy, how do people attach the fans to the rad? The other thing is a fan behind the rad can only suck through at about 1 atmosphere, whereas a fan in front can blow at as many as it can, therefore more air flow.

[Karan]

I mentioend this to my brother not long back as I was thinking about going the RS Turbo leccy fan route, thinking I would be saving myself a couple of BHP.

He said not to bother as the viscous will flow more air and stops working above 40mph.
.

He's making a not unreasonable assumption that the fan moves the air through the rad at a certain speed, and at about 40MPH that speed is matched by the ram effect through the radiator. Hence the mechanical fan is doing no work, and consuming no energy, even if the viscous coupling is lock (which it probably won't be, as the ram effect will be providing more than enough cooling).
To provide the same amount of airflow as a mechanical fan, an electric fan will consume about twice as much power from your engine (via the altenator).

this is true but my electric fan only ever comes on during traffic.... when power isnt an issue.... it stops pretty much as soon as i start moving.... so electrical power loss via alternator really isnt an issue.... electric fan really is a no brainer.. only prob is some sort of electrical failure in the system...

[Karan]

Yeah but when you're sitting in a traffic jam at idle the fan is only doing 900rpm when it's cooling efect is needed most. Manufactureers switched to leccy fans as they have more control, when you're sitting still at idle they can be going flat out disipating all the heat built up from just before you stopped. I'm gonna switch to leccy, how do people attach the fans to the rad? The other thing is a fan behind the rad can only suck through at about 1 atmosphere, whereas a fan in front can blow at as many as it can, therefore more air flow.

my fan is a blow thru in front of the rad.... u can make up a bracket....like demlotcrew has done or just use special cable tie type clips to secure it agianst the rad

[Wilson]

I'm gonna switch to leccy, how do people attach the fans to the rad?

I'd like to know this, assuming we are talking RST fans?? (Used to have 3 spare RST fans, but gave them all away with all bits when I sold the RS!!!! )

[hoshy]

Makes sense to me too. I may try this on the RR too, just to see.

[Demlotcrew]

I mentioend this to my brother not long back as I was thinking about going the RS Turbo leccy fan route, thinking I would be saving myself a couple of BHP.

He said not to bother as the viscous will flow more air and stops working above 40mph.
.

He's making a not unreasonable assumption that the fan moves the air through the rad at a certain speed, and at about 40MPH that speed is matched by the ram effect through the radiator. Hence the mechanical fan is doing no work, and consuming no energy, even if the viscous coupling is lock (which it probably won't be, as the ram effect will be providing more than enough cooling).
To provide the same amount of airflow as a mechanical fan, an electric fan will consume about twice as much power from your engine (via the altenator).

Ok so your stuck in traffic and the clutch is locked you then pull away and accelerate to 50mph but the fan is locked so if anything the air would be trying to speed the fan up but its locked!

Also i think its more to do with engine speed than road speed. (but i do understand what your saying) I can remember watching a plane film and the old prop based planes would have to rotate the blades on the propeller to stop drag.

Ive done it and it cost me less than getting a new belt driven clutch fan.

Also it does make a difference!

A

[Brianmoooore]

I mentioend this to my brother not long back as I was thinking about going the RS Turbo leccy fan route, thinking I would be saving myself a couple of BHP.

He said not to bother as the viscous will flow more air and stops working above 40mph.
.

He's making a not unreasonable assumption that the fan moves the air through the rad at a certain speed, and at about 40MPH that speed is matched by the ram effect through the radiator. Hence the mechanical fan is doing no work, and consuming no energy, even if the viscous coupling is lock (which it probably won't be, as the ram effect will be providing more than enough cooling).
To provide the same amount of airflow as a mechanical fan, an electric fan will consume about twice as much power from your engine (via the altenator).

Ok so your stuck in traffic and the clutch is locked you then pull away and accelerate to 50mph but the fan is locked so if anything the air would be trying to speed the fan up but its locked!

Also i think its more to do with engine speed than road speed. (but i do understand what your saying) I can remember watching a plane film and the old prop based planes would have to rotate the blades on the propeller to stop drag.

Ive done it and it cost me less than getting a new belt driven clutch fan.

Also it does make a difference!

A

And if your electric fan is on it is absorbing plenty of power from the engine via the altenator

[Karan]

He's making a not unreasonable assumption that the fan moves the air through the rad at a certain speed, and at about 40MPH that speed is matched by the ram effect through the radiator. Hence the mechanical fan is doing no work, and consuming no energy, even if the viscous coupling is lock (which it probably won't be, as the ram effect will be providing more than enough cooling).
To provide the same amount of airflow as a mechanical fan, an electric fan will consume about twice as much power from your engine (via the altenator).

Ok so your stuck in traffic and the clutch is locked you then pull away and accelerate to 50mph but the fan is locked so if anything the air would be trying to speed the fan up but its locked!

Also i think its more to do with engine speed than road speed. (but i do understand what your saying) I can remember watching a plane film and the old prop based planes would have to rotate the blades on the propeller to stop drag.

Ive done it and it cost me less than getting a new belt driven clutch fan.

Also it does make a difference!

A

And if your electric fan is on it is absorbing plenty of power from the engine via the altenator

yeh but it will stop when u start moving...the power loss in traffic os not an issue./.....

[hoshy]

I don't think the fan stop as soon as you start moving do they? surely tit won't be off until the temp drops, thus it would draw power whilst accelerating from lights in traffic. Which would suggest that there's not much benefit. it would also be of interest to see how much juice the leccy fan draw in comparison to the loud music you listen to. hmm moving off topic now sorry

given that the car will always need cooling when in traffic I doubt there's any difference between electric or viscous when the car needs additional cooling. we need a good old empirical study.

maybe somebody with a gtech could do tests with and without the fan connected. given we've already discounted the in-traffic differences the test can be viscous fan vs. no fan

[hoshy]

maybe need to think of the torque differences of 4/6 pots and engine capacity. I'd bet a 4pot would see more benefit than a 6pot

[Karan]

I don't think the fan stop as soon as you start moving do they? surely tit won't be off until the temp drops, thus it would draw power whilst accelerating from lights in traffic. Which would suggest that there's not much benefit. it would also be of interest to see how much juice the leccy fan draw in comparison to the loud music you listen to. hmm moving off topic now sorry

given that the car will always need cooling when in traffic I doubt there's any difference between electric or viscous when the car needs additional cooling. we need a good old empirical study.

maybe somebody with a gtech could do tests with and without the fan connected. given we've already discounted the in-traffic differences the test can be viscous fan vs. no fan

gtech and RR testing is pointless as we're talking 1-2hp and there are too many variables suh as air temp etc......

ud be surprised how quickly the leccy fan stops as the water temp drops very very rapidly when u start moving at like 4ompg again..... are u serious,u telling me u care about the 2hp when accelerating just after traffic.... its not as if ure gonna be flat out... the water cools down quickly once moving and the leccy fan switches off.... the viscous remember is controlled more by the air temp around the viscous unit? am i correct? so responds less quickly and will switch off way after the water has dropped to a required temp.... see what im saying...

advantage here is that the exact temp can be controlled with leccy fan but cant with viscous

[Widge]

As far as I see it, an electric fan will be flat out whatever the engine revs (when it's on obviously) which means the car won't cook when idling (if somthing goes wrong or it's really hot etc) which was what worried me about the viscous.

It has the added advantage of never having to get that bloody left hand threaded viscous b1tch off again!

[hoshy]

I don't think the fan stop as soon as you start moving do they? surely tit won't be off until the temp drops, thus it would draw power whilst accelerating from lights in traffic. Which would suggest that there's not much benefit. it would also be of interest to see how much juice the leccy fan draw in comparison to the loud music you listen to. hmm moving off topic now sorry

given that the car will always need cooling when in traffic I doubt there's any difference between electric or viscous when the car needs additional cooling. we need a good old empirical study.

maybe somebody with a gtech could do tests with and without the fan connected. given we've already discounted the in-traffic differences the test can be viscous fan vs. no fan

gtech and RR testing is pointless as we're talking 1-2hp and there are too many variables suh as air temp etc......

ud be surprised how quickly the leccy fan stops as the water temp drops very very rapidly when u start moving at like 4ompg again..... are u serious,u telling me u care about the 2hp when accelerating just after traffic.... its not as if ure gonna be flat out... the water cools down quickly once moving and the leccy fan switches off.... the viscous remember is controlled more by the air temp around the viscous unit? am i correct? so responds less quickly and will switch off way after the water has dropped to a required temp.... see what im saying...

advantage here is that the exact temp can be controlled with leccy fan but cant with viscous

All I'm really saying is that instead of speculating maybe we could actually find out. I've been told that Bexley tried the electric fan conversion and found that there was *UP TO* 7bhp.

"are u serious,u telling me u care about the 2hp when accelerating just after traffic"

You must've misunderstood me mate. Most of what I was talking about was completely discounting any in traffic difference.

Fair point about how quickly the electric turns off before the viscous cools down.

[boybimmerm3]

the main reasons for electric fans being used are for better fuel cosumption and more accurate cooling of the engine.

[Widge]

JJ, I saved that woman's dog

"JJ, one of the hamsters had a panic attack...."

Gotta be may fave film ever

PULL OVER!!!

[Toby_Unna]

yeah i agree with boybimmer and with widge. a leccy fan can kick in and out as often as it wants to keep the engine at its optimum temp.

i gave up on viscous when it failed on my m535i. bought a new one and the car was nasty to drive, once the whole thing was hot in traffic in hot weather, it took ages to get the thing to disengage, felt noticeably less powerful and sounded like a hoover

and to cap it off, the thing wouldn't keep the car cool when i went to le mans and it was really hot, after 15 mins sitting in traffic i had to start reving the engine a bit to blast cool air through.

saying that it might have been a bad (euro car parts) fan, my 528i never made the wooshing noise to loudly and never used to overheat, and i never touched the viscous fan in 3 years.

end of the day i found a citroen bx in a breaker which had 2 square fans, put one in the m535 and one in the 335, cost Ԛ£15 per car plus a few wires and a relay pattern viscous fans cost Ԛ£25 or something

[Widge]

Right, I have two blanking bolts on the thermostat housing, a la

What car do I need to get a fan switch thingy from so that it fits the thread on these holes? Anyone done it ? I just don't want to have to use one of those in hose thingys, I want it to look original to all intents.

[Karan]

Right, I have two blanking bolts on the thermostat housing, a la

What car do I need to get a fan switch thingy from so that it fits the thread on these holes? Anyone done it ? I just don't want to have to use one of those in hose thingys, I want it to look original to all intents.

u can put it there which would be nice or u can just put it in the drivers side of the rad.... my rad is a replacement one from gsf/euros and has a provision for a sensor on the drivers side... ures may have this also....

[Martinaston]

Sorry to stick my nose in but does anyone know of any original BMW parts to make the fan run after the ignition is turned off ?
I'm thinking of trying to put an electric water pump in as well (earlier thread)