Have an acewell speedo and it has ability to display two temperatures. I would like one of these to be inlet air temperature but they don't have an open element sensor to do this (the closed one works just fine but it responds too slow to be of any use in a turbo engine). I figure I can just replace it with an OEM air temp sensor of similar resistance. I measure it (roughly) as:
Ice water 0 degrees - 300000 Ohm
Room temp 20 degrees - 138000 Ohm
Boiling water 100 degrees - 7000 Ohm

These seem a lot higher than most OEM sensors but maybe someone knows of something that will work. Otherwise what about carefully drilling holes in the casing of the closed element sensor. I assume it has some sort of thermister inside but no idea if it is full of resin or anything.

You might be lucky and find that the curve for each is the same, but probably not. I took some resistance readings of a standard Acewell sender. I will see if I can find them for you.

If dissimilar, you could maybe look at the converter from https://www.spiyda.com/magento/index.php/

Those were the readings from a standard acewell sensor (closed element). Actually the cheapo ntc thermistors on ebay seem to have similar curves so maybe i can cut the thermistor out of an oem air sensor and replace with another

Ah, sorry. Misunderstood.

If I remember correctly the Acewell does not show temperatures under 20 or 25oC. I assume this is because fluids are not often in that range and/or the sender and associated electronics are tuned for a higher temperature range, nearer 100oC. Therefore larger measurement unceratainty at lower temperature of a voltage divider sensing the signal, perhaps.

What range of temperatures do you get on the inlet?

That range is ok. I'm only interested in the air temp when it goes past 50 degrees as not running intercooler.