Thermal Fan Sensor/Switch: Whats the optimal Mount Location on a RB?

[SLVRBAKSLPZ]

All,

Currently getting a radiator w/ shroud and 16" brushless fan fab'd up. I will be using the sensor to switch on the fan. I will be using a stock thermostat(76.9c) with a 175-195f sensor switch.

I planned on getting the sensor thread bung welded to the lower half of the radiator near the outlet hose (mimicking the AC fan stock sensor switch location)

However, I've read much on that the switch needs to be mounted near the hottest point which would be near the upper hose.

Some of what I've read also states that it needs to be close to the thermostat. Most of that info is non-RB specific as some motors thermostat is located on the upper hose pipe.

Should the switch be close to the coolant temp sensor for thermostat??

Whats optimal when it comes to a RB?

[Dose Pipe Sutututu]

Personally I would use your ECU to control the fan, the OEM water temp sensor on the outlet from the plenum would be the best spot to sample water temperature.

If you use a SSR or an OEM fan controller (from another car)you could even duty cycle your fan so it gently ramps in as water temperature increases and say goes from 30% duty at 75°C and to 100% by 85°C as an example. Far more sophisticated and superior than an on/off thermo switch.

Makes everything a bit more premium.

 

[SLVRBAKSLPZ]

3 minutes ago, Dose Pipe Sutututu said:

Personally I would use your ECU to control the fan, the OEM water temp sensor on the outlet from the plenum would be the best spot to sample water temperature.

If you use a SSR or an OEM fan controller (from another car)you could even duty cycle your fan so it gently ramps in as water temperature increases and say goes from 30% duty at 75°C and to 100% by 85°C as an example. Far more sophisticated and superior than an on/off thermo switch.

Makes everything a bit more premium.

 

I thought about just doing the ECU route. With the Spal Brushless tech, the fan is basically variable speed on its own with the switch (low speed @175F /max @195F).

I also thought about getting one of the radiator hose sensor provisions to mount the switch, since it seems the upper is deemed the most optimal location.

 

 

 

[Dose Pipe Sutututu]

Nice!

If that's the case, just install that sensor on plenum outlet. 

You're sampling water that is being expelled out from the motor, you would assume it's the best location.

[SLVRBAKSLPZ]

6 minutes ago, Dose Pipe Sutututu said:

Nice!

If that's the case, just install that sensor on plenum outlet. 

You're sampling water that is being expelled out from the motor, you would assume it's the best location.

Thanks!

The sensor is 3/8 so i may not exactly get it on the plenum but its def going up top! I just found one of those hose adapter in 3/8 on the ebay.

I'll just plug the bung that they welded on the bottom and delete the OEM harness for the than AC fan sensor switch. The new fan is gonna do the job.

[GTSBoy]

If it were me, I'd just build a controller on an Arduino. Fit it with a little trim pot or two, put it in a sealed box, and use the sensor location in the rad tank. The trim pots would allow the on and off points to be adjusted, rather than relying on hard switching points. The logic in the controller could be as sophisticated or as simple as you like. You could even have extra RTDs or TCs looking at external air T, engine bay T, etc, to inform how hard to run the fan.

I'd see it as an opportunity to experiment with programming some fuzzy logic. Might turn out to be complete overkill, but good fun.

But, if you have the capacity to run it from the ECU, almost any other option is verging on silly. No extra sensors required, all sorts of additional logic available at the twitch of a mouse, etc.

Edited April 24, 2023 by GTSBoy