Since I need a ton of air temp sensors in my GTR build, I’m taking a crack at making my own using a very fast response bead NTC element. Tony Palo already makes a really kick ass one that uses a TDK glass bead NTC element that has a ‘still air’ thermal response time of ~3s. That constant is an indication of the time to cool 63.2% of the way from a chosen heating point to ambient air temperature in still air. In fast moving air the response time would be much much faster, and in a liquid even more so.

I built these two test units using a similar NTC sensor from Cantherm that has a similar response time but slightly lower thermal mass. Since I have two ports in my Pre IC pipe I can directly compare both of these to not only a GM AIT, but also a low mass thermocouple. I also have a couple of other glass diode elements to try out.

For reference, the thermal response time of the typical ‘fast response’ GM AIT sensor is on the order of 15s. Both of these types of NTC sensors are of the fastest available in that form factor. An exposed tip thermocouple can have a response time as low as 1s in still air, and .01s in liquids, but the accuracy can be as low as +/- 5C.

I used a 3M epoxy potting compound to put the sensor inside a small 1/8NPT to hose adapter along with some Tefzel wire. I made these probes stick out a little bit more than normal because of the location of the adapter I need to use them in. I’ll post up data in a few days as to how they compare.

If you are looking to buy something to put in your build, just get the ones from T1. If you want to experiment with getting that extra 1%, follow along. 😉