Different MAT sensors?

[JeepsAndGuns]

So now that I have my test harness set up, I decided to start testing a couple sensors from my jeep 4.0 so I would know what I can and can not use.
I pulled the jeep MAT from my engine and tested it against the gm MAT I bought new at the parts store. The gm sensor reads correctly on my datalog dash, and I used a heat gun to test it. The jeep MAT uses the same plug, but the ohm range is incorrect. When its hooked up, instead of reading 70* like the gm one did, it read closer to 50*.
So I am going to have to swap to a gm MAT. Only problem is, the gm one uses larger threads than the jeep one. The gm sensor has the same thread size/count as the CTS (I think 3/8 npt?). However the jeep mat has smaller 1/4-18 npt threads. Other than the thread size, they are almost identical.
So I was wondering, is there a gm MAT from some other car/truck that is compatable with a 7727/$8D that has 1/4-18 npt threads?
I suppose if there is not one, you might be able to re thread the gm sensor. Looking at them, the "cage" around the elements are the same size on both, just the gm one has more material around the main body for the larger threads. I think you might be able to chuck it in a lathe and turn it down a hair and re thread it. But only going down that route if there are no other compatable mat's.
Anyone know of any?

Heres a pic, jeep on the right, gm on the left.

[EagleMark]

I don't know what size it is but 1996 4.3L CPI has a MAT in intake like the ones you pictured.

Only others I know of are plastic and go in air intake, IAT. Which may be easier and more accurate if that is what your bin/mask/xdf used from factory. Temps in intake manifoild are differant/hotter then air in air cleaner or air tube to air cleaner. 1991-92-93 Caprice, Roadmaster has one in air filter and 1994-95-96 Caprice Roadmaster, Camaro etc.. LT1 engine has one in air intake tube.

But CTS from just about all GM EFI all read same as IAT and way cheaper, last FOREVER there, just a little slower to respond, it's what I've always used and can't feel a difference or see one in data?

[dave w]

Years and years ago, I used the Standard Motor Products Illustrated Parts Guide to figure out sensor interchangeability. The guide would show thread pitch and thermistor ranges. I poked around the online version of the SMP guide and it's not as easy as flipping pages in a book that has about 1200 pages.

Anyway, the challenge I see is most newer / smaller sensors are going to be metric thread pitch.

I'd try machining a CTS down to the correct O.D on a lathe, and try cutting the tread pitch I needed on the machined CTS. Maybe the CTS has enough metal to be machined and re-threaded?

dave w

[EagleMark]

I did shave down a three wire CTS to fit into an oil pan drain plug. Then someone else did it and ran out of metal? Look up the Oil Temp Sensor in drain plug thread...

If it fails just plug the hole and add an IAT...

[dyeager535]

From now on if I intend to try and rethread sensors, I'm going to have a junkyard spare to practice on first. As Mark mentioned, the three wire (brass) sensor in question was too thin ABOVE the threads. I tried the same on a two wire CTS, and it turned out to be steel with a brass core, and solid all the way through. I have another CTS, same application, and it is brass. But I had that one turned on a lathe and it didn't snap like the three wire. Just be careful.

If I wasn't worried about leakage/sealing (pipe thread) then I'd ONLY cut the sensor down where there are threads, no further up the body. Still won't guarantee it doesn't twist off, but the portion of the body where there are threads on the one that broke, was thicker than the portion above the threads.

[JeepsAndGuns]

I will be running $8D, witch is set up for a intake mounted MAT.
I remember the thread about the oil temp sensors. This one I only need the threaded part re threaded. I just wanted to know if there was any already avalable with the correct thread size before I have one machined. I will drop this one off at the machine shop and see what they can do. If it gets distroyed, then I'm only out $18 for another sensor.
I will only swap to a IAT if there is no other options, as the ecm/bin will be expecting a MAT, not a IAT. Like you said, different temps between the two.

[EagleMark]

Just chuck up the sensor end in drill mounted in vise and spin it, use a file to shave it, get close to diameter and thread it with die. I did that one in 20 minutes or so and never done it before.

[RobertISaar]

could recalibrate the conversion table to match the jeep sensor.

[EagleMark]

could recalibrate the conversion table to match the jeep sensor.

Now, now, don't make it complicted! Were trying to bolt a part on here...

Never thought of that...

[dave w]

could recalibrate the conversion table to match the jeep sensor.

I hadn't thought of that either. I'm not sure I'd know how to recalibrate. Is there an 8D table to change? Maybe the hex code has to changed? Just wondering?

I tend to build / parts source an EFI conversion setup by GM Make / Model / Year.

dave w

[RobertISaar]

i may be a machinist, but if i can avoid potentially scrapping good parts, i avoid it.

as long as you could hold the two sensors in identical conditions(let's say throw them in a pot of water of something?), then just need to get the sensors around to a calibration point(there are 17), see what temperature the GM sensor is showing, then switch to the Jeep sensor and move the value at that portion of the table around until it matches what the GM sensor was showing. maybe switch back and forth again to confirm it's still the same.

obviously, this is done much easier with an emulator or at least a bank switch.

[Six_Shooter]

Why has no one suggested drilling the intake for the larger thread? That's what I do in a situation like this.

[EagleMark]

Probably to avoid removing the intake, it's a running vehicle... but yes that is a simple solution.

[Six_Shooter]

I've drilled intakes on vehicles for this, you just have to be careful, use rags, some grease, a vacuum and your head.

[JeepsAndGuns]

could recalibrate the conversion table to match the jeep sensor.

Wow, that can be done?
I would have no clue how to do it. Only problem I see, is finding a controlled environment to put the sensors in to get proper readings from them. Would the ADX also have to be changed?

I would also rather mod a $18 sensor than the intake on my jeep. So no drilling it. I might give what mark said a try, though I dont have any type of drill that will hold this thing.