This picks up a discussion about the installation of an Omori EGT gauge. In particular the instructions indicate a 1/8 PT tap for the sensor.

Originally posted by J-Spec Tuning

Hi Dennis,
The probe goes into a bung that is provided with the gauge set. The hole that needs to be drilled and tapped to accomodate the bung is 1/8" PT (not NPT).
Thaison

Originally posted by jjunior887
I just found some info on the PT standard, it looks like it's the Japanese form of BSPT which is the british standard Pipe thread tapered. Not the same as NPT which is mainly used here in the US. Here's a Link (http://mdmetric.com/tech/tict.htm) to where I got some info. For you guys with the omori EGT gauge, what size tap di you use?-James

I agree that PT and BSPT may be the same. The thing is the directions say 1/8 PT not 1/8" PT. I think the 1 is pitch in mm and the 8 is thread count per cm. The measures would be metric not imperial.

If the above is correct then the conversion (according to their table) means the tap would be between 25 1/2 and 20 1/4 per inch. Neither of which is close enough to work properly.

I'm interested in figuring this out because I have a hole that was made for my Autometer EGT which was 1/8" NPT and now I need to make the Omori sender fit which is 1/8 NPT. It looks like they have a bung that mates with the 1/8" NPT but the trouble is finding one. Thaison from J-spec is looking into it for me right now. Here's where I got the impression that they make one somewhere
http://members.fortunecity.com/jjunior887/0bab56c0.gif -James

EDIT: I just noticed after looking through these directions that they are for the Defi gauges but it's all pretty much the same, we just don't have the control unit.

Thanks for scanning that in. I don't have my EGT yet, the one I ordered is a special order that Thaison at J-SPEC was very helpful in arranging.

The strange thing is that picture would indicate that the 1/8PT and 1/8NPT are identical. My impression was that James' original note indicated this wouldn't be the case. My knowledge of taps has gone from zero to the limits of what is on the site James referenced - so I don't know for sure what this means.

Anyone that can provide what size drill bit and exactly which tap to use for this EGT sensor please let us know. I would like to have the tools in hand when my EGT arrives. :)

Actually it's not the same, if you look closely it says "1/8PT OR 1/8NPT(optional part)", the 1/8NPT bung is the one I'm looking for.-James

James,

Have you tried to put the Omori sleeve in your old hole? Maybe just see how far you can finger tighten it with lots of wd40 and stop as soon as you get any resistance and back it out. I would think if you don't get any resistance after about 10 turns (which I think (8 threads per cm) would be about 1.25 cm of depth or almost an inch) then the current tap is close enough to work.

Just a thought.

Ed.

Originally posted by jjunior887
Actually it's not the same, if you look closely it says "1/8PT OR 1/8NPT(optional part)", the 1/8NPT bung is the one I'm looking for.-James

Ahh, very good point. In that case I am sure Thaison will find the optional sleeve and it should fit your old hole.

The thread that Thaison referred to for an install:

http://forums.nasioc.com/forums/sho...threadid=182975

This looks to be an autometer install.

Here is an install that did not tap the exhaust:

http://www.clubwrx.net/forums/showthread.php?s=&threadid=20114

On this install the person got a bung with no external threads with internal threads that matched the probe sleeve. Drilled a hole and then welded the bung outside the exhaust pipe over the hole. That is a good option too - if you have the right internal threading in the bung. :lol: Unless the Omori comes with a welded unthreaded bung, the search for the right bung could be as long as the search for the right tap.

One good thing about using a welded external bung, only the thin probe inserts into the exhaust flow. Putting the threaded sleeve bung directly into the exhaust will leave more of an obstacle in the exhaust flow if you thread the sleeve to the point where its threads go all the through the pipe wall.

Anyone ever find that 1/8 PT tap?

1/8PT (Japanese) is 1/8 -28 BSPT. Omori USA verified for me. I just installed the Omori sensor today and it looks like they were right :)