Digital Tuning Coolant Temperature Sensor Microsquirt

Nightstang00 · Feb 17, 2020

I have a 93 gt with a on3 turbo kit and a microsquirt. I currently run an auto meter coolant temp gauge and that sensor is installed where the factory sensor is on the driver side. I removed the heater core pipe due to not using the heat or ac. I used the hole that the metal heater core pipe threaded into the intake manifold for the relocated coolant temp sensor that the ecu uses which originally is in the heater core pipe that I removed. My gauges were both pretty even prior to this, now I am getting a 15-20 degree difference sometimes. I also changed my radiator and now am running the turbo setup. I want to ensure the gauge that the microsquirt reads (relocated into heater core pipe mounting thread in the intake manifold) is accurate. If this wouldn’t work, does anyone have any suggestions ?

a91what · Feb 17, 2020

Pictures please. The ect sensor needs water moving past it, if it's in a deadhead location it may not read correctly.

Nightstang00 · Feb 18, 2020

I circled the only two places I have reading coolant. The passenger side is the side in question. The driver side had never been touched. That side is reading higher. The driver side gauge stays between 200-210 and sometimes under 200. Thepassenger side gauge goes around 170-190 which is connected to the microsquirt

a91what · Feb 18, 2020

They are on different sensors styles, 10* offset between them is not uncommon. I always believe the one the ECU is connected to.
170-190 is a large swing, what thermostat is in it?

Nightstang00 · Feb 18, 2020

a91what said:
They are on different sensors styles, 10* offset between them is not uncommon. I always believe the one the ECU is connected to.
170-190 is a large swing, what thermostat is in it?

I just got a new duel pass radiator, new t state 180 , and moved that sensor to the place it’s at now on the passenger side. Just wondering if there is a better place for it. I don’t think that the bottom of the sensor touch’s the coolant unless the coolant travels up a tad to reach the bottom of the sensor since it has an adapter in there to have the sensor fit.

General karthief · Feb 18, 2020

I would say the bottom of the sensor is in the coolant, it likely will not read if air is trapped there, if in doubt just loosen up the sensor with the system up to temp and let a small amount of coolant seep out.

a91what · Feb 18, 2020

Modern efi is designed to run at 200-210* The correct thermostat will get you up to a stable temperature, you want the fans setup so that the temperature only moves about 5* or so if they are electric the ECU can control them.

Nightstang00 · Feb 18, 2020

a91what said:
Modern efi is designed to run at 200-210* The correct thermostat will get you up to a stable temperature, you want the fans setup so that the temperature only moves about 5* or so if they are electric the ECU can control them.

So that temp is what I’m showing on the gauge that wasn’t changed. It’s the other sensor that now is reading lower, which is connected to my Microsquirt. I’ll check to see if there is any air in the system and if when it’s hot I can loosen it up and coolant comes out.

a91what · Feb 18, 2020

Double check your ECU thermistor calibration, remember the thermistor do not read linearly and sometimes a small discrepancy can stack up.
Write down the hot idle values for both gauges, then in the morning do the cold value. Is there a difference in the cold value? If there is then we need to modify the calibration completely.
You will also need to use a multimeter and get a resistance reading from the pins on the ect sensor with it unplugged. Do this hot and cold.
Then I'll help you fix the offset issue.

Nightstang00 · Feb 18, 2020

a91what said:
Double check your ECU thermistor calibration, remember the thermistor do not read linearly and sometimes a small discrepancy can stack up.
Write down the hot idle values for both gauges, then in the morning do the cold value. Is there a difference in the cold value? If there is then we need to modify the calibration completely.
You will also need to use a multimeter and get a resistance reading from the pins on the ect sensor with it unplugged. Do this hot and cold.
Then I'll help you fix the offset issue.

Awesome I’ll get the values tonight. I’ll double check to ensure the sensor is calibrated let you know.

vristang · Feb 20, 2020

What kind of sensor is hooked up to the gauge? Is it a 3 wire V-ref sensor similar to the ECT?
The ECT will still function if it is in an air pocket, but it will just read the temperature of the air that it is in. Not accurate coolant temp, but it still works the same way.
I would NOT crack the cooling system at temperature/pressure. Being sprayed by hot pressurized coolant would ruin your day...

Not sure I read your post right, did you add the turbo the same time you noticed these differences? Or was it just the heater tube that you removed?

Nightstang00 · Feb 20, 2020

vristang said:
What kind of sensor is hooked up to the gauge? Is it a 3 wire V-ref sensor similar to the ECT?
The ECT will still function if it is in an air pocket, but it will just read the temperature of the air that it is in. Not accurate coolant temp, but it still works the same way.
I would NOT crack the cooling system at temperature/pressure. Being sprayed by hot pressurized coolant would ruin your day...

Not sure I read your post right, did you add the turbo the same time you noticed these differences? Or was it just the heater tube that you removed?

I removed the coolant tube and changed the radiator and thermostat and installed the turbo all at once. This is the picture of where I relocated the coolant sensor

a91what · Feb 20, 2020

vristang said:
What kind of sensor is hooked up to the gauge? Is it a 3 wire V-ref sensor similar to the ECT?
The ECT will still function if it is in an air pocket, but it will just read the temperature of the air that it is in. Not accurate coolant temp, but it still works the same way.
I would NOT crack the cooling system at temperature/pressure. Being sprayed by hot pressurized coolant would ruin your day...

Not sure I read your post right, did you add the turbo the same time you noticed these differences? Or was it just the heater tube that you removed?

The ect and iat sensors are 2 wire thermistors... they are referenced to sig grd not 5v signal. The ECU has an internal pullup installed to convert this to something the ECU can measure.

Nightstang00 · Feb 20, 2020

Nightstang00 said:
Awesome I’ll get the values tonight. I’ll double check to ensure the sensor is calibrated let you know.

Haven’t got a chance to get the numbers but I did add in calabration setting -the ford sensor. It shows this now, but the temp gauge wasn’t incorrect prior to all the changes I did.

Digital Tuning Coolant Temperature Sensor Microsquirt

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