DIY rear diff cooler build - Advice

Joris_44 · 10-19-2022, 08:21 PM

Put a 1.5way Kaaz LSD in my weekend/track car and it's running too hot, even w/ Z1 aftermarket cover. Melted 1 set of bushings so my winter project is building a rear diff cooler in the spare wheel well. I've got the pump, lines and cooler squared away but I'm stuck on the control. I don't want to use a mechanical thermostat but would like to use a digital thermostat triggered by the diff oil temp sensor (that I need to install) to activate the pump and fan relay. I looked but I can't find any thermostats for automotive that can read the diff oil temp sensor and then activate a relay. Does anyone know?

370z NA with a lot of mods

Rusty · 10-19-2022, 08:40 PM

I used off/on switches for the pump and fan. I just watch the diff temp gauge. When it gets to around 230F. I'll turn it on. The highest I've seen was 270F. With both pump and fan on. It will dropped to 170F.

SeeThruHead · 10-19-2022, 09:12 PM

the sensor will output a specific voltage
you can connect a relay that will activate at a specific voltage off of the sensor circuit.

use something like this to control the pump (comparator relay control circuit)
LM393 DC 12V 2Bit Voltage Comparator Relay Control Circuit Module

compare a reference voltage vs the voltage reading from the sensor. if the sensor is higher, relay turns on the pump

when the voltage drops because temps drop the relay turns off.

EDIT:
that board is overkill for you use case, you could probably create this circuit from scratch, but I'm not good enough with this electrical stuff to know how.

MotorvateDIY · 10-19-2022, 10:50 PM

Quote:

Originally Posted by Joris_44

I looked but I can't find any thermostats for automotive that can read the diff oil temp sensor and then activate a relay. Does anyone know?

I think this may help.... I have re-purposed a Nissan Sentra coolant sensor to read the differential oil temp and manual transmission temperature on my G37.

From here I could enable a relay to turn on a cooling fan, if required.

Joris_44 · 10-20-2022, 06:44 AM

Quote:

Originally Posted by Rusty

I used off/on switches for the pump and fan. I just watch the diff temp gauge. When it gets to around 230F. I'll turn it on. The highest I've seen was 270F. With both pump and fan on. It will dropped to 170F.

Thx Rusty. 100F drop! Wow that’s great, more than I hoped for

Joris_44 · 10-20-2022, 06:47 AM

Quote:

Originally Posted by SeeThruHead

the sensor will output a specific voltage
you can connect a relay that will activate at a specific voltage off of the sensor circuit.

use something like this to control the pump (comparator relay control circuit)
LM393 DC 12V 2Bit Voltage Comparator Relay Control Circuit Module

compare a reference voltage vs the voltage reading from the sensor. if the sensor is higher, relay turns on the pump

when the voltage drops because temps drop the relay turns off.

EDIT:
that board is overkill for you use case, you could probably create this circuit from scratch, but I'm not good enough with this electrical stuff to know how.

Thanks! seetruhead. This is exactly it. I was looking at clunky thermostats with a display but this you can use with a nice automotive oil temp gauge. Now I need to buy my sensor and do some calibrating in the kitchen :-)

Averying · 10-20-2022, 07:58 AM

Quote:

Originally Posted by SeeThruHead

the sensor will output a specific voltage
you can connect a relay that will activate at a specific voltage off of the sensor circuit.

use something like this to control the pump (comparator relay control circuit)
LM393 DC 12V 2Bit Voltage Comparator Relay Control Circuit Module

compare a reference voltage vs the voltage reading from the sensor. if the sensor is higher, relay turns on the pump

when the voltage drops because temps drop the relay turns off.

EDIT:
that board is overkill for you use case, you could probably create this circuit from scratch, but I'm not good enough with this electrical stuff to know how.

Quote:

Originally Posted by SeeThruHead

the sensor will output a specific voltage
you can connect a relay that will activate at a specific voltage off of the sensor circuit.

use something like this to control the pump (comparator relay control circuit)
LM393 DC 12V 2Bit Voltage Comparator Relay Control Circuit Module

compare a reference voltage vs the voltage reading from the sensor. if the sensor is higher, relay turns on the pump

when the voltage drops because temps drop the relay turns off.

EDIT:
that board is overkill for you use case, you could probably create this circuit from scratch, but I'm not good enough with this electrical stuff to know how.

This seems like a pretty cheap/easy solution but am I stupid to think that with this board paired with a diff temp sensor, you’re not going to actually know what temp the relay is activating at? There’d have to be some controlled calibration off-car before install.. am I right?

Sent from my iPhone using Tapatalk

SeeThruHead · 10-20-2022, 09:47 AM

i think you have to look at the specs of the sensor to match temp to output voltage

Averying · 10-20-2022, 10:18 AM

Quote:

Originally Posted by SeeThruHead

i think you have to look at the specs of the sensor to match temp to output voltage

And then mess with the pot on the board to get the relay to activate at the desired sensor output voltage. Makes sense

Sent from my iPhone using Tapatalk

Rusty · 10-20-2022, 12:35 PM

Here's the thread on my diff cooler.

MA Motorsports Diff Cooler Install

Joris_44 · 10-21-2022, 07:28 AM

Quote:

Originally Posted by Averying

And then mess with the pot on the board to get the relay to activate at the desired sensor output voltage. Makes sense

Sent from my iPhone using Tapatalk

That’s what I though too. I was going to use Near boiling water (with a kitchen thermometer) to set the switching point and install an automotive oil temp gauge in parallell

Joris_44 · 10-21-2022, 07:37 AM

Quote:

Originally Posted by Rusty

Here's the thread on my diff cooler.

MA Motorsports Diff Cooler Install

Nice! I looked at that one! But it won’t fit with the Hks exhaust so I’m moving into the spare wheel well. Way too much dead air there anyway.

From there few 10 min sessions I did on track before overhearing I loved how the car handles. Did you like the upgrade to clutch lsd too?

10-19-2022, 08:21 PM	#1 (permalink)
Joris_44 Base Member Join Date: Jul 2017 Location: Chicago Posts: 5 Drives: 17 370Z Sport Blk M Rep Power: 8	DIY rear diff cooler build - Advice Put a 1.5way Kaaz LSD in my weekend/track car and it's running too hot, even w/ Z1 aftermarket cover. Melted 1 set of bushings so my winter project is building a rear diff cooler in the spare wheel well. I've got the pump, lines and cooler squared away but I'm stuck on the control. I don't want to use a mechanical thermostat but would like to use a digital thermostat triggered by the diff oil temp sensor (that I need to install) to activate the pump and fan relay. I looked but I can't find any thermostats for automotive that can read the diff oil temp sensor and then activate a relay. Does anyone know? 370z NA with a lot of mods

10-19-2022, 08:40 PM	#2 (permalink)
Rusty Ronin Samurai - Assassin Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 68 Posts: 35,217 Drives: 2011 Nismo GM 6M Rep Power: 2684438	I used off/on switches for the pump and fan. I just watch the diff temp gauge. When it gets to around 230F. I'll turn it on. The highest I've seen was 270F. With both pump and fan on. It will dropped to 170F. Joris_44 likes this. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html

10-19-2022, 09:12 PM	#3 (permalink)
SeeThruHead Track Member Join Date: Jun 2020 Location: Toronto Posts: 716 Drives: Red '18 Sport Manual Rep Power: 23498	the sensor will output a specific voltage you can connect a relay that will activate at a specific voltage off of the sensor circuit. use something like this to control the pump (comparator relay control circuit) LM393 DC 12V 2Bit Voltage Comparator Relay Control Circuit Module compare a reference voltage vs the voltage reading from the sensor. if the sensor is higher, relay turns on the pump when the voltage drops because temps drop the relay turns off. EDIT: that board is overkill for you use case, you could probably create this circuit from scratch, but I'm not good enough with this electrical stuff to know how. Joris_44 likes this. __________________ My Build thread STH Build Plan Thread Images too big fix here Last edited by SeeThruHead; 10-19-2022 at 09:23 PM.

10-20-2022, 09:47 AM	#8 (permalink)
SeeThruHead Track Member Join Date: Jun 2020 Location: Toronto Posts: 716 Drives: Red '18 Sport Manual Rep Power: 23498	i think you have to look at the specs of the sensor to match temp to output voltage __________________ My Build thread STH Build Plan Thread Images too big fix here

10-20-2022, 12:35 PM	#10 (permalink)
Rusty Ronin Samurai - Assassin Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 68 Posts: 35,217 Drives: 2011 Nismo GM 6M Rep Power: 2684438	Here's the thread on my diff cooler. MA Motorsports Diff Cooler Install sx moneypit likes this. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html

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