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Sensor setup question

MoTeC M1 Software Tutorial

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I was just making sure that Im doing this correctly. I have 3 temp sensors that all read differently when all fluids and the ambient should essentially be the same. The car is in my garage and its 70F here. I hit the oil pan and the upper water neck with a temp gun and they both read 69F. My oil temp sensor reads 65F, the ECT sensor reads 59F and the Air Inlet Temp sensor reads 71F.

I have all the sensors setup with their proper cals from the menu (OE toyota coolant temp, GM air temp and GM oil temp). since the numbers should all read the same for the most part I switched to a manual cal and offset the whole table until all sensors are reading 69F. I am just making sure that this is the correct way to apply an offset to these sensors.



It's not uncommon to see small differences between different sensors and if you want to get accurate comparable results then you're best to use the same sensor. Simply offsetting the calibration isn't going to work as all you can be sure of is that the temp readings are same at whatever temperature you've been at when you've offset the cal - Above of below this it's going to be anyone's guess as to whether you're right or wrong.

It is possible to develop your own calibration or at least check your calibration if you have an accurate digital temperature sensor. I've got a digital voltmeter with a k type thermocouple input that I've used for this purpose. You can put the sensor you want to calibrate (or even better, both sensors at the same time) in a container of oil (a small pot works well) and then slowly heat the oil while monitoring the temperature vs sensor voltage.

With the M1 ECU you also need to make sure that your voltage reference is set correctly.

If all three temp sensors are in air, what do they read? Has the engine been recently run? has the ambient temp been consistent, or is it coming up from a lower temp?

You will have thermal mass to deal with with the fluids, so if they have been in an area that was colder, then they will take longer to react to the change in temp than a air temp sensor will.

I have found this with my car, in that I have individually calibrated each of the sensors in my engine, but looking at the temps after a cold soak over night, the oil and coolant temps take longer to get up to ambient than the air temp sensors do. Even the air temp sensors will have different response curves, dependent on their location in the engine, and the material that they are installed in.

As the temp sensors have non linear translations, you can't just move the scale up and down to try and match it, as you may end up making it worse in a different location. You would be better off to try one of the other calibrations to see if one of them matched the temp that you are seeing on a separate, calibrated, sensor, such as a K Type thermocouple.

The car had been sitting for a few days in the garage with out running. So obviously this is not a standard practice. I'm using the pre-defined calibrations for the GM oil temp sensor and the toyota coolant temp sensor. It just seems that they should read the same temperature in my situation and they're 10F different. Thanks for the response!


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