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Thermocouple vs Temperature Sensor for Intake Air Temperature

Practical Standalone Tuning

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Wondering if anyone has some feedback/advice regarding intake air temperature measuring devices. I have an Elite 1500 and am currently planning my concentric layout for the harness.

I have an 8 channel thermocouple that will feed exhaust temperatures to the ECU via CAN. I have 6 channels left on the thermocouple box and was wondering if running a thermocouple for intake temperature sensor is a good idea or if anyone has run it this way.

The main benefits I am thinking with running the thermocouple for intake air temps are, faster time response constant on the thermocouple vs normal resistance temp sensor and will also free up one of the analog inputs on the ECU that could be use for another sensor.

Any thoughts?

I usually only see TC used for IAT in cases such as un-intercooled promod etc where the temps are above the working range of a standard thermistor. In general a good quality thermistor designed specifically for automotive IAT measurement will be faster than most common TC's. I know you can get specialised TC's manufactured with thin wires, exposed junctions and special refractory encapsulation for high speed air temp measurement but they are $$$.

As some general points a common TC can be more accurate than a thermistor, but slower, more expensive, more sensitive to emi etc, less capable of error detection, requires an amp, specialised wire and connectors.

A thermistor is cheap, fast, easy, could be less accurate - especially at the upper end of their working range, but generally well suited to the job. I personally wouldnt move away from the proven road unless I was expecting my air temps to be above say 130°C regularly.

While it's possible, I think you should use a normal solution for a critical engine sensor like intake air-temp. Use your Thermocouple inputs for data logging, (like both sides of a radiator or intercooler to see the temperature drop). Just use a standard fast-response air temp sensor.

Awesome, thank you for the feedback it is much appreciated. I already have a fast acting intake air temperature sensor (from RIFE sensors) so I will maintain my original plan of using that as the source for IAT's to the ECU.

David, I like that idea for using the additional TC inputs for radiator and intercooler pre and post temps, I might even throw one at the GBOX and DIFF now that I think about it.

If I had an 8 channel I would have one in each runner if possible.

It is a 13B rotary (2 rotors) so only two are needed for the exhaust gas temperatures.

Has anyone used thermocouples for water temp sensors. you would have to use a closed tip thermocouple but the slow moving temp of the coolant would'nt make a closed tip thermocouple response time much of an issue.

does anybody know if there are any issues using the thermocouple in correction or compensation tables?

the other issue might be longevity, do thermocouple sensors rust away in coolant quicker than normal thermistor sensors.

Nothing wrong with using thermocouple type sensors as long as you have the necessary temperature range, resolution and reliability.

I've pretty much stopped using anything but K type thermocouples for builds that have the budget to throw a single 8 channel expander in the mix. Standardizes sensor bodies to a point as well as connectors. There's a little spend in proper interconnects and wire but the convenience is worth it to me.

That said, there are a lot of sub par parts such as said connectors and wire, not to mention the thermocouples themselves because they're very easy to manufacture at scale for industries that integrate them, so my suggestion is do homework on where you're sourcing parts.

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