thermostat, thermo fans and switch questions

[river]

Hi,

if its swithced on at 65 degrees at the bottom then once the engine gets upto temp then the fans will run constantly and thermostat will close again.

Well I am assuming the bottom hose and subsequent water temp on the lower hose (ie coming out of the radiator) is at a lower temp than the temp at the top, where it come sout of the engine and into the rad.

So, if (using just example numbers) the bottom is at 65deg when the top is at 90 deg, when we need the fans switched on, then you need to fans to come on (again just example numbers) when the bottom is 60-65 deg.

What I am trying to say is if you switch the fans on via the bottom hose temp then you need to take into account what the top hose temp will be. If you use the top hose temp then you want your fan to come on at 90deg. If you want to use the bottom hose to switch the fan on then you need it to switch on at 65 deg - assuming an approx 30 deg rise in temp from what temp comes in compared to what temp comes out of the engine.

So you could use the temp from either the top or bottom to switch on your fans, but the temp for activating the switch would be lower if you use the bottom hose temp.

seeyuzz
river

[Shakotan_Aaron]

but if your cooling the water to (example) 65 degrees then wont a 82 degree thermostat close up?

[river]

Hi,

It will if it is at the bottom hose. But if the thermostat is at the top then it needs to open at the hotter temp of water coming out of the engine.

The cooling system is a closed environment. Hot water comes out at the top of the engine and goes into the top of the rad. Cooler water comes into engine from the bottom of the rad.

If you are using the hotter water, from the top, to activate the thermostat and/or fans then you need the thermostat to open at (say) 80deg and the fans to come on at (say) 90deg.

If you are using the cooler water, from the bottom, to activate the thermostat and/or fans then you need the thermostat to open at (say) 70deg and the fans to come on at (say) 80deg.

If the cooler water coming into the engine (from the bottom of the rad) is too hot then you can guarantee the water coming out of the engine will definitely be too hot also. Similarly, if the temp coming out of the engine is too hot, then you can rest assured the water coming into the engine (from the bottom of the rad) will also be too hot. They affect and follow each other.

My personal preference is to have the temp sensor, thermostat and fan switch to be all in the same location - be it the top or the bottom. Moreso I like to know the temp of the water that actually comes out of the engine and use that as my reference as opposed to the temp of the water going into the engine.

seeyuzz
river

[allencr]

Don't give up.
How much power would our viscous fans waste if they only worked according to engine heat and not by the radiators condition.

[crownv8]

Hi,

It will if it is at the bottom hose. But if the thermostat is at the top then it needs to open at the hotter temp of water coming out of the engine.

The cooling system is a closed environment. Hot water comes out at the top of the engine and goes into the top of the rad. Cooler water comes into engine from the bottom of the rad.

If you are using the hotter water, from the top, to activate the thermostat and/or fans then you need the thermostat to open at (say) 80deg and the fans to come on at (say) 90deg.

If you are using the cooler water, from the bottom, to activate the thermostat and/or fans then you need the thermostat to open at (say) 70deg and the fans to come on at (say) 80deg.

If the cooler water coming into the engine (from the bottom of the rad) is too hot then you can guarantee the water coming out of the engine will definitely be too hot also. Similarly, if the temp coming out of the engine is too hot, then you can rest assured the water coming into the engine (from the bottom of the rad) will also be too hot. They affect and follow each other.

My personal preference is to have the temp sensor, thermostat and fan switch to be all in the same location - be it the top or the bottom. Moreso I like to know the temp of the water that actually comes out of the engine and use that as my reference as opposed to the temp of the water going into the engine.

seeyuzz
river

I understand what you are saying, but, the electric fans only need to turn on when the radiator has little or no air flow through it. Ie, when the car is stopped or slow driving and there is little or no temp differece from top to bottom. Remember the radiator won't cool the water without air flow. That is why you have a 90-95 degree switch in the bottom hose. If the water going in at 95ish comes out the bottom at 95ish and the fans turn on.

After they have run for a while the water temp at the bottom hose will reduce to 85ish and the fans will turn off with only a very slight change of temperature at the top. If you are still stuck in traffic :-( the temperature between the top and the bottom hose will equalise again and the fans will turn on. Once you move off again and get on the freeway :-) and the radiator has good air flow the bottom temp will drop down to 80ish and the fans don't need to run.

If you have the switch in the top hose and you are doing some "track work" for example the engine temp usually rises and if the switch is up the top the fans will come on even though the radiator is doing its stuff and cooling the water. In this scenario the fans can actually slow or disturb the air flow though the radiator while the car is driving at speed and cause more problems, like overheating.

In the end, as long as the car doesn't overheat it doesn't really matter. But this has been the thinking on fan switches for many many years.

Cheers,
Shane.

[Shakotan_Aaron]

river, i agree with the location for the reference for a temp gauge being in the top.

im talking a JZ engine here and the thermostat is in the bottom hose (feeds strait threw the water neck/thermostat into the pump).

if the water is any cooler then 82 degree which is the temp of the thermostat then its going to close perhaps not completely but enough to slow the water flow making the water stay in the engine longer and the water entering the top of the radiator will actually be hotter. this is what im talking about with the thermostat and fans fighting each other for temp control. if the thermostat was in the top hose, then what you are saying would be 100% correct.


oh and i have no idea how much HP is lost by the viscus fan. not enough for me to be worried by

edit: this (possibly byass) website claims 8.5% power loss
http://www.kenlowe.co.uk/fans/consumers/fans03.html#no3

[allencr]

oh and i have no idea how much HP is lost by the viscus fan. not enough for me to be worried by
edit: this (possibly byass) website claims 8.5% power loss
http://www.kenlowe.co.uk/fans/consumers/fans03.html#no3

Thanks but, the viscus fan ref isn't about power at all, its about what the radiator needs & when it needs it, like more airflow when what''s passing through it remains too hot.
Also, the thermostat's place isn't important to the switch or radiator or fan, only that it sense the engine coolant.

[river]

Hi,

Agreed. While some power would be lost by turning the belt, I find it hard to beieve it would consume 8.5% of the engine power in doing so. The viscus fan works well and silently. I never know, by audible reference, when it's kicked in and I don't notice any difference to engine performance when it does. Sure, I see the temp go up a little and then drop down to normal, so I know the fan is coming on and off as required. The viscus fan, unlike the switched electric fan, has a soft activation/de-activation cycle. The fluid slowly heats up (inside the fan unit) and it gets thicker which allows the fan to grab more (ie less slippage on the hub) and suck in more air. Similarly when the temp goes down the fluid gets less thick and the fan unit slips more and sucks less air. The electric units are either on or off and you notice this because there is no "soft" activation/de-activation.

On Trini, who runs a big kick arse thermo fan, you certainly know when its activated. The engine labours a little as it is driving the loaded alternator, which must supply the current to run the fan. While stationary you can certainly hear the electric fan when it cuts in, but if the car is moving (even slowly) you dont hear it.The fan certainly displaces a lot of air as you can feel a warm breeze coming from under the car if you stand beside it when the fan comes on.

I am trying to figure out how a thermostat on the bottom hose would work, especially when the engine is is cold and has just been started. The thermostat has a small bypass which allows some water to flow even when it is fully closed which means water does flow through the system, but only a minimal amount. If you have a thermostat on the bottom hose then how does it get hot enough to open? Initially warm water would be coming out of the engine and into the radiator, which cools the water, so wouldn't it take longer to open a thermostat which is on the bottom hose? And, if so, by the time it does open the water coming out (from the engine) be very hot because the thermostat is activated upon the cooler radiator water?

Is a thermostat which sits on the bottom hose different in design or have different open/close parameters to a thermostat that sits at the top of the engine?

seeyuzz
river

[Shakotan_Aaron]

if i had all the set-up and it wasnt such a hassle id go a hydro fan due to the awesomeness of it.

4A also has the thermostat in the bottom hose.

yes you are correct, a tiny bit can bass bit it really is only a tiny bit. note the hole with the jiggly pin in the top.



in my mind a TRD thermostat wouldn't be that bad of an idea, they are 71degree openers and arnt that expensive. but this lot should have worked as its as it came from factory and JZ motors are otherwise a great design.

[crownv8]

The thermostat in the 1UZ is in the bottom hose. I'm pretty sure the 4cyl Camry is the same.

The bulb to activate the thermostat is inside the engine not facing the radiator so it will warm up with the coolant locked inside the engine just the same as a top mount thermostat. So it should operate similar to a top mount one. I don't know why Toyota decided to put the thermostat in the bottom hose?????

My 1UZ has an 82 degree thermostat and the engine usually sits between 85 and 90 degrees.

Be careful putting cold thermostats in. The EFI system is designed to run at around 85 degrees. Making it run colder will result in poor fuel economy amoungst other things.

Also, I prefer the viscous fans, they move a lot more air than most electric fans. I just got rid of the electric one's on my car and put the viscous back on with a shroud. Much happier. The car doesn't run hot if I'm stuck in traffic and the air con likes it better too.

Cheers,
Shane

[Sciflyer]

I dont know about poor fuel economy, i run a TRD thermostat in my daily UZZ31 (which is around 71C) and i still get ~10L/100km, never noticed any difference in fuel consumption

[Bananaman]

im using a new china/ebay alloy radiator for mx83, i tried a jza80 radiator (figured it was rated for the motor) but it was too tall.

Same as me then. I too was going to run it in the bottom hose for the same reason as you, for whatever reason i gave in and ran it on the top hose... The end result is it still runs exactly how i want it, it's just ugly / in your face. With said china radiator i have EL fans and a 92-87 temp switch in one of those speco adapters (leaky... will tap a thread in thermostat housing when i can be bothered). When i'm driving, fans are off. When i stop, they kick in - and work well enough that it will cycle on and off as it sits there.

Not much clearance to the motor though, engineer may not like it when i finally get it done. The extra thickness of the alloy rad puts it pretty close

[Shakotan_Aaron]

Be careful putting cold thermostats in. The EFI system is designed to run at around 85 degrees. Making it run colder will result in poor fuel economy amoungst other things.

So today i completely flushed the system, tested thermostat and the rest.

Also i noted the points at which the idle/map seemed to change as ive been curious about people saying that TRD and other low thermostats wont run the motor hot enough. the temps where 40deg (reached that quickly) then a second change at 65. these where not just my imagination as they where spot on with the defi. So if a person where to run a lower temp thermostat they should be able to get away with a 72deg TRD or billion item without it being in this warm up enrichment mode.

[river]

Hi,

Not much clearance to the motor though, engineer may not like it when i finally get it done. The extra thickness of the alloy rad puts it pretty close

Is clearance an issue with engineering? I have about 2 mm between my electric fan and the engine. It's a very tight fit, but what do you expect when trying to fit an FMIC, oil cooler, air-con unit and radiator on an RA28 without changing the front end looks. Mind you, it is a big fuckoff 16inch mother of a fan.

I'm looking to get a triple core radiator next, so that will be fun and games trying to get it to fit.

seeyuzz
river

[Shakotan_Aaron]

Hi,



Is clearance an issue with engineering? I have about 2 mm between my electric fan and the engine. It's a very tight fit, but what do you expect when trying to fit an FMIC, oil cooler, air-con unit and radiator on an RA28 without changing the front end looks. Mind you, it is a big fuckoff 16inch mother of a fan.

I'm looking to get a triple core radiator next, so that will be fun and games trying to get it to fit.

seeyuzz
river

I didnt have an issue with clearance on my car in regards to engeneering, mine is also REALLY close, i had to trim the studs on the water pump. maybe run 2 fans? maybe 2 10" fans or something?