Cooling system with electric fans

[MrOizo]

I am almost done with my electric fan setup and have been thinking about how i should go about this.

Looks like the norm is to have a fan switch on the engine outlet and have them turn on at a certain temp.

What i have been thinking is would it be better to have the sensor on the outlet (bottom hose) of the radiator as thats the temp that matters with what is going into the engine.

if the water coming out of the radiator is cool then the water coming out of the engine will be...

if the water coming out of the radiator is coming out hot, then the engine will make it hotter...

Is this worth looking in to? obviously the sensor will have to detect a lower temp.

anyways.... thoughts?

cheers.

[strx7]

On everything i have ever put an aftermarket ecu on (rx7, 5sgte corolla, 2jz surf) I have had the temp sensor for the ecu on the feed into the radiator, and the temp sender for the guage on the cool side. This allows ya to see the temp drop across the radiator.
Most vehicles generally run around between 90 and 95 celcius into the radiator. I have my fans set to switch on at 93 and off again at 90. In the corolla I switch them on at 96 and off again at 93. The corolla has a long, end tank type radiator which sees alot of temp difference in to out and if the fans turn on at anything below around 91, when they kick in the thermostat closes due to it being on the cold side of the cooling system.

[Stealer Of Souls]

If you put the switch on the bottom I would think it would turn on too late... The water coming out the bottom would be too hot and THEN the fans would switch on. You'd potentially end up with a large slug of water that is too hot getting sent back in for further heating...

[MrOizo]

Ok thanks guys.

Looks like i'll have to put the sensor up top with the water temp sensor. Just have to 'tune' the fan controller.

Cheers.

[strx7]

If you put the switch on the bottom I would think it would turn on too late... The water coming out the bottom would be too hot and THEN the fans would switch on. You'd potentially end up with a large slug of water that is too hot getting sent back in for further heating...

If you used a temp dependant switch and were placing it after the radiator you'd just use a cooler switching sensor, somewhere about 75-80 degrees would be in the ball park, application dependant.

The beauty with using an aftermarket ecu is you can switch things at whatever

[matt dunn]

Your thermostat will be low eighties temp wise,
and rad fan switches are mid nineties.

In therory the thermostat should be wide open and the water should be flowing arond the whole system flat out all at the same temp at the point the fans switch on.

If it's at the bottom of the radiator, the water in the radiator will cool pretty quick and the fan will not say on long,
but not much will have been cooled either, so it will cycle on of quite fast.


If you run it in the top hose it will keep running until the water coming out of the engine has cooled, so it will stay on longer, and also switch of for longer.

[MrOizo]

If you put the switch on the bottom I would think it would turn on too late... The water coming out the bottom would be too hot and THEN the fans would switch on. You'd potentially end up with a large slug of water that is too hot getting sent back in for further heating...

If you used a temp dependant switch and were placing it after the radiator you'd just use a cooler switching sensor, somewhere about 75-80 degrees would be in the ball park, application dependant.

The beauty with using an aftermarket ecu is you can switch things at whatever

I thought about placing it in the stock place where the hydro fan sensor is. i dont have the hydro setup so the hole just has the sensor bunging it.

[MrOizo]

Your thermostat will be low eighties temp wise,
and rad fan switches are mid nineties.

In therory the thermostat should be wide open and the water should be flowing arond the whole system flat out all at the same temp at the point the fans switch on.

If it's at the bottom of the radiator, the water in the radiator will cool pretty quick and the fan will not say on long,
but not much will have been cooled either, so it will cycle on of quite fast.


If you run it in the top hose it will keep running until the water coming out of the engine has cooled, so it will stay on longer, and also switch of for longer.

cheers for that. will have to decide where in the rad its going

[Py7h0n]

Trust me - JZ with electric fans is going to require them on most of the time once the temp gets up to normal.

Once mine are on, thats is, until I turn the engine off. Mine are configured to turn on >93 and off <90.

[strx7]

depends on your JZ and the size of your radiator. My JZ powered surf run pretty cool most of the time. Only time it gets hotter than 96 outta the engine is on the speedway track.

[matt dunn]

Trust me - JZ with electric fans is going to require them on most of the time once the temp gets up to normal.

Once mine are on, thats is, until I turn the engine off. Mine are configured to turn on >93 and off <90.

and what temp is the thermostat? If it's an 87 that will be why,
not enough difference between the thermostat temp and the sw point

[MrOizo]

Looking at the repair manual for the 2JZGTE, the opening temp for the thermostat is 80-84 deg C

I measured the temp of the water leaving the radiator of TOYWGN's JZX100's outlet hose and that was around the 60-65 deg mark. is this what i should be aiming for?


Is this temp ideal for a water temp to be leaving the radiator?

[Quint]

Necro!

MrOizo, I'm in the same situation atm, Where did you decide to put the switch in the end? and what did you use as your switching temp (on and off).

[matt dunn]

Most factory cars switch the radiator fans on at between 97 and 100deg,
and off again in the low 90's.

and the sensor needs to be on the engine side of the thermostat.

[MrOizo]

On the JZA70, there is a sensor port for the Hydro fans and i used that. not too sure what there is on the other A70 radiators.

I cant remember what i had mine switching at anymore - will need to measure it when i get it going again.

I do know it was sitting at ~90deg when running

Necro!

MrOizo, I'm in the same situation atm, Where did you decide to put the switch in the end? and what did you use as your switching temp (on and off).

[Quint]

Cheers.

[allencr]

The fan is there to cool the rad. when there is inadequate air flow through it and the coolant going into the engine isn't getting cooled down enough. That is why ANY factory setup you can find has the fan sensor on the rad. outlet/engine inlet side.
Using the engine outlet temp to control the fan, from the same location as your temp. gauge, will turn the fan on almost all the time whenever the engine is under a load & running hard. Even during Winter at +100kph.

[matt dunn]

The fan is there to cool the rad. when there is inadequate air flow through it and the coolant going into the engine isn't getting cooled down enough. That is why ANY factory setup you can find has the fan sensor on the rad. outlet/engine inlet side.
Using the engine outlet temp to control the fan, from the same location as your temp. gauge, will turn the fan on almost all the time whenever the engine is under a load & running hard. Even during Winter at +100kph.

Really as 99% of the modern cars I work on the fans is controlled by the ECU through the ECU temp sensor which is always on the engine side of the thermostat. And I work on cars all day every day.

switches in the radiators went out almost as long ago as cars with steel or copper tanks on the radiators.

Under almost all driving conditions the temp sensor should read close to the thermostat temp, say 81-87 deg,
and the fan will only turn on when the temp gets too high, around 95 deg.