Noticing my IAT reading looking off so I'm pretty sure the sensor calibration is wrong.

Anyone have a voltage map for the Triumph sensors?

 

Its the same resistance as the stock FD sensor.

 

I've been looking into this as well. The readings are definitely about 10* off from the stock sensor. They were close enough on the PFC but the Haltech seems to be more noticable. On the PFC, if the car sat overnight the coolant and IAT temps would match but the haltech is almost always off by 10* or so, at least in the 50-70* range.

 

I'm going to have to double check that today. I don't recall my IAT being off through the Haltech.

 

There is a tolerance to both the ADC of any ECU, as well as the sensor. 10* as a corner case does not sound surprising at all.

I recently went through a similar exercise with a Speedhut water temp gauge vs. Adaptronic and the stock sensor.

I actually characterized both inputs with a lab variable resistor, both sensors over temperature, replaced both sensors with new and characterized vs. the old sensors, and compared all the data to the expected calibration curves. Everything was within spec, but both setups were on the opposite ends of the tolerance to form a worst case.

Below are some pictures of how I characterized the sensors. Please excuse the kitchen laboratory

 

lmao, i thought i was the only one to do that stuff!

 

😆

 

Yup. My CTS and EGT sensors coincide, IAT is always 10-15* higher. Trying to come up with a good way to make a voltage map.

 

So I ended up doing some testing with the Triumph sensor and thought I'd post my findings here in case anyone needs the data.

The Testing:
First I placed the IAT sensor in ambient room air and documented the resistance value using a multi meter. I used a k-type thermocoupler to (digital bbq temp probe) to measure air temps. I verified the accuracy of the thermocoupler at ambient air temp to be accurate.

Then I placed both sensors in the freezer to get a low end reading.

Next I placed both sensors into a glass jar and sealed the top with plastic wrap to create a chamber. Both sensors were suspended in air, about the same depth into the jar, and not touching the glass or each other. Placed the jar into a pot of water on the stove in order to manipulate the temp of the air inside the chamber. I started by putting ice into the water to get some cool air temp numbers.

I documented resistance values about every 10F in a range of about 32F-180F. I repeated the test 3 or 4 times to ensure the accuracy of the data. I also contrasted the resistance values seen while heating the air temp versus cooling, as these values proved to show small variations (prob due to sensor response lag). I tried to take this into consideration in my voltage map by choosing values that represented something between the heating and cooling values.

The Math:
Next I needed to translate the resistance values into voltages that the ECU can understand.
I used this equation: (5V/(pull up resistance + measured resistance))measured resistance = Sensor voltage

It's kind of hard to write algebra here, so in other words...
* Add the pull up resistor value (Haltech uses 1000Ohm pull up resistor) + the resistance measured at the sensor. This is the total resistance.
* Divide the circuit voltage by the total resistance. This is a 0-5V circuit so we use 5V here. This is the current running through the circuit.
* Multiply the current by the sensor resistance and you get the voltage the ECU will be seeing coming from the sensor.

I found this article to be really helpful:
https://www.hpacademy.com/previous-w...ommon-sensors/

The Data:
(deg F = Ohm = Voltage)

32.2F = 4000 = 4V
46F = 3500 = 3.89V
54F = 2750 = 3.67V
65F = 2300 = 3.48V
78F = 1950 = 3.31V
90F = 1440 = 2.95V
103F = 1070 = 2.58V
117F = 800 = 2.22V
120F = 750 = 2.14V
130F = 600 = 1.88V
140F = 500 = 1.67V
150F = 400 = 1.43V
160F = 340 = 1.27V
170F = 310 = 1.18V
178F = 270 = 1.06V

I created a custom sensor in the Elite and plugged in some voltage values from 54F-150F (I live in CA where we don't know what cold is). To my satisfaction, when viewing live sensor data after sitting all night my ETG, oil temp, water temp, and IAT all agree +/- a few degrees. I've attached my .cal file here for anyone who would find it handy.

Disclaimer: I haven't got to test this outside of just idling because my FD is the bane of my existence and not road worthy at the moment. So if you choose to use this data you should verify yourself before trusting the accuracy.

 

I have a T1 glass air temp sensor now, stock coolant temp, AEM oil temp and Haltech egt thermocouples. I did the same and did my own calibration on the AIT sensor because I believed it was off as it was also 10-15 degrees higher than oil temp/ coolant temp. What I found was it was dead nuts accurate already. The egt reads the lowest, the oil temp and coolant temp are within a few degrees of each other, and the IAT is the highest. Coincidentally, this directly correlates with the height of their mounting locations.