Nissan 200SX Club - South Africa

hmmm...

@ calibrator... i guess that my experience in the IT business obviously counts for shit-all then!

i am obviously also taking from experiences that i've had in the motor industry, and i was trying to repeat an explanation that i got from an established mechanic once.

i also did a quick search on Wiki, and i got a response exactly like the one i tried to explain:

Wikipedia wrote: A fan clutch is an automatic device frequently used in automotive cooling systems. When the engine is cool or even at normal operating temperature, the fan clutch partially disengages the engine's mechanically-driven radiator cooling fan, generally located at the front of the water pump and driven by a belt and pulley connected to the engine's crankshaft. This saves power since the engine does not have to fully drive the fan.

However, if engine temperature climbs beyond the clutch's pre-determined setting, the fan becomes fully engaged, thus maintaining or lowering engine temperature.

Most fan clutches are viscous or "fluid" couplings combined with a bi-metallic sensory system similar to that in a thermostat.

regardless - here is where i am coming from:

1. you're right about the fluid in the coupling being silicone. and one property of THAT silicone is that the hotter it gets the more solid it becomes. in fact, it gets very close to being a near complete solid. so it makes sense that when the silicone between the coupling's plates is cold, the plates slip over each other. when it gets hotter, the silicone basically glues those plates together as it gets closer to becoming a solid.

2. it was a mercedes benz, if i am not mistaken, that i was describing. that was the car where the fan was barely spinning while things were cold. at that stage you could stop the blades with you hands and the engine would carry on idling. in fact, the fan would barely spin even if you revved the engine. but the hotter the engine got, the faster the blades would spin. so unless it was some drug that someone had slipped into my drink, that is what i experienced. but perhaps the germans do things differently to the japs.

3. i had never actually thought that deeply about the direction of flow of the water, but now that you mention it - it makes sense (i guess) to switch on the fans based on the temperature of the hot side. it also makes sense that the radiator fills from the bottom and runs towards the engine from the top. however...

4. i have never had any problems with the running temperatures of my ca18det. NEVER. so i wouldnt go as far as calling it a FUCKUP. my engine used to run at halfway on the stock temp gauge. which is what is recommended by the FSM. since i removed the aircon system it now runs ever so slightly below that halfway line??? go figure!!! i hope thats not to much of a fuckup either.

5. i would assume that when the water temperature switch turns the fans on, that the water flowing into the engine would be about 91 degrees celcius. i assume this because i hope that the thermostat is working properly, and at that temperature would therefore be open about 10 degrees prior to this. my assumption leads me to believe that the engine is operating at roughly the right temperature, which i believe to be about 100 degrees. i hope that is right, because i'm not about to go to my garage to get out my FSM now!

6. lastly, even on the drift track, my stock water temp needle stays just below the half mark. the water temp guessometer i have installed barely ever reads over 100 degrees. but dont forget thats on the cold side!

1st fact
You have heard one explanation and seen one car. I have seen hundreds all doing the same thing maybe that should count for something.

I have heard these rumours of locking viscous units but I have yet to see one and it makes absolutely no sense at all as I will explain. You must realise that there are various kinds of silicone pastes some slip as in a viscous fan drive and some lock with heat as in a LSD. You will also find that when a viscous is tired it doesnt transmit drive so you will get the effect that the fan is not turning very well.

After working for 15 years in dealerships I would well advise you to ignore what most mechanics tell you of a cars functioning.

Now if you would take the trouble to step up a car with a functioning viscous you will more than likely see exactly what I have described.

Why have cars been equipped with electric fans? To remove a power sucking device from the engine ie: a permanently engaged fan.

Why do cars have viscous fan drives? To allow the engine to be cooled at low engine speed which more than likely coincides with low road speed. As engine speed rises so does road speed and so does the power required to drive the fan. Hence the need to disengage the fan.

You will also find that most of the vehicles that have a viscous drive unit also have a electric fan as a backup and for use when the aircon is engaged.
Now a simple test
Start a car with a viscous fan.
Rev it up gradually and watch the fan it will start slowing down at some point.
Now get the car up to operating temperature and do the same test and you will observe the same thing.
Now switch the car off hold the fan with your hand or something and start
the car. The fan will attempt to turn but will happily stand still while the engine is running.

End of discussion untill you can produce a car and prove me wrong in which case I will admit I have seen something new.

i dont consider it the end of discussion if you say it is?

also, i mentioned one car that i had seen behave this way. and you just assume that its the only one i've ever seen.

i would love to find the car that behaved that way, but the chances are unlikely and we both know it.

but let me get this right:

you think a viscous fan should be running fully at low engine speeds?
you think a viscous fan should begin disengaging as the speed of the engine increases?

that correct?

this discussion led me to do more research, and everything i've found so far is nicely summarised by this little article:

The thermal viscous fan drive is a silicone-fluid-filled coupling used to connect the fan blades to the water pump shaft. The coupling allows the fan to be driven in a normal manner. This is done at low engine speeds while limiting the top speed of the fan to a predetermined maximum level at higher engine speeds.

A thermostatic bimetallic spring coil is located on the front face of the viscous fan drive unit. This spring coil reacts to the temperature of the radiator discharge air. It engages the viscous fan drive for higher fan speed if the air temperature from the radiator rises above a certain point. Until additional engine cooling is necessary, the fan will remain at a reduced rpm regardless of engine speed.

Only when sufficient heat is present, will the viscous fan drive engage. This is when the air flowing through the radiator core causes a reaction to the bimetallic coil. It then increases fan speed to provide the necessary additional engine cooling.

Once the engine has cooled, the radiator discharge temperature will drop. The bimetallic coil again reacts and the fan speed is reduced to the previous disengaged speed.

so there are obviously different designs out there. i dont remember seeing the little bimetallic coil, but then i dont always pay so much attention to detail. and i was wrong in saying that it depends on engine temperature. it seems fan operation is related to radiator discharge air temperature!

compared to the car i mentioned seeing - that car was cold when the fan wasnt engaging at all. perhaps it wasnt working properly. i dont know.
when it got hotter the fan speed at idle was significantly higher.

dude, without trying to offend you at all, is there a particular reason you're so aggressive when it comes to your own opinions???

Damn, to much to read. If you are looking for a decent electric fan, get the BMW Aircon fan, its from a 5 series, not sure what exact model, its a 2 stage fan, first same as regular fan and second, very strong. If I remember correctly, its a sucking fan.

You mean, that BMW fan sucks?

A thermostatic bimetallic spring coil is located on the front face of the viscous fan drive unit. This spring coil reacts to the temperature of the radiator discharge air. It engages the viscous fan drive for higher fan speed if the air temperature from the radiator rises above a certain point. Until additional engine cooling is necessary, the fan will remain at a reduced rpm regardless of engine speed.

Strangely enough none of the cars I have worked on have had this system.
How much heat gets transmitted to the viscous through the pump shaft? May cause a problem with the bimetalic spring engaging point?

Mebbe I am aggressive cause of all the "internet experts" telling me I dont know shit.
By all means prove me wrong and I will be the 1st to admit I was wrong but dont tell me I am wrong because of something that was read which may or may not apply.

LOL - you called me an "internet expert".

i have never claimed to be, but get this - i am not stupid either...

and the explanation i gave was factual, and was backed by experience, which, granted, was not my own. seeing a single car operate is barely experience, i agree with that. anyway, i reckon differences in opinion are good for both knowledge building and creative thinking.

i actually never knew about that coil until searching the topic. i've noticed them before, but never wondered what they were for. i always thought that ambient heat and heat through the shaft (as you mentioned) was the way it worked.

How much power does your viscous fan take to run?? How much power does your alternator take to keep up the voltage when your electric fans are on??

The way I see it is you will probably only gain 1-2kw which is nothing. If you ae looking for that 0.01 sec on the 1/4 mile, buy a faster car!!!

Ill stick with my viscous.

I didn't read all the mombo jumbo, I guess it all makes sence and and and...great!

I did my own electric fan swop with temp sensors and stuff and my car never overheats nothing, my temp guage doesn't even reach the halfway mark on the guege.

In my opnion, just the fact that you have more space to work infront of the enjine is worth it, no matter what gains and what not.

did my own electric fan swop with temp sensors and stuff and my car never overheats nothing, my temp guage doesn't even reach the halfway mark on the guege.

Derek, yes I know your sx as good as mine these days. Which I dont like and you know I dont like it, is the fact that you have to set the idle higher than the norm, since the electric fans mod. I just hope I never have to go that route. But the most important is that you are happy.

That was one of the reasons, if the fans or the lights were put on the idling dipped and went back up but I hate that so that is why I set my idling up, in any case as u say it works for me.

CEEVEE needs to shave the dudes in his avatar!!!

CEEVEE needs to shave the dudes in his avatar!!!

Bwahahahahhahaha It seems he does

VeeCee I never said u were an "internet expert" U do seem somewhat more clued up than the average surfer. However I get it almost every day from some "expert" or another and it really pisses me off.
EG: some twat on meeting me for the 1st time told me flatout that unichips are kak and dont work.

Now I dont know how many he has fitted but I believe its none so I am curious how he arrived at that fact. Thats the kind of character I can strangle.