There is a blocked off hole in the rear iron which I think is the oil pressure sensor plug. I want to use my defi 1/8" PT (not NPT) sensor. Would it thread in and seal fine? my search shows many different types of pipe threads as possible answer (NPT, BSPP, BSPT, BSP, BPT, etc.), and I am little overwhelmed. I want to make sure I have the right thread on that defi sensor (1/8" PT) for 20b rear iron..., and if not exactly what adapter I need. thank you.

 

I'm pretty sure its 1/8NPT, as I have used an extension adapter on the rear iron to fit the FD pressure sending unit

My DEFI D-gauge uses an 1/8npt thread, are you sure 1/8NP is no the same as NPT?

 

Defi made some US version which used NPT fittings. I'm pretty sure my defi gauges use something called "PT" which isn't the same as NPT. Some say they are interchangeable... some say don't do it. I guess I can just screw it on and keep an eye on it.

so the adapter you used had 1/8" NPT male fitting which threaded into the rear iron fine?

 

IIRC yes,

just lightly thread it in there and see if it binds or if you can get a few good turns on it without effort

 

let me ask for a second opinion before I take the car out of commission for a few days

can anyone confirm the oil pressure sensor thread in the rear iron?

 

I don't own a 20b but standard metric pipe is BPT. Did Mazda use full metric standard? I don't know.

 

I can't speak for a 20b, but Aaron Cake indicates that the oil pressure sensor in a 12A is 1/8 BPST.

https://www.rx7club.com/general-rota...gauge-1088078/

 

You're right, its actually BSPT, as its the same from the FC. The FD iron is 1/8NPT I think. But, I didn't even know this until now, and I successfully threaded the FD oil pressure sender into the block using an extension from home-depot with 1/8NPT. It appears the NPT will fit into the BSPT female, may just take a few more turns or a little more thread lock/tape. No issues here, no leaks, no cross threading etc.

 

thank you all. I did some extra research because there were too many nomenclatures. Here's what I found.

straight thread (wrong thread for rear iron): BSP == BSPP == BSSPI == BSPF == BSPG == PS == R == G (these are all f'ing same thing)

taper thread (correct thread for our rear iron): BSPT == PT == KR == Rc (all same thing)

so we need 1/8" BSPT, PT (defi), KR, or Rc threads for our rear iron.

Onto this NPT business. NPT and BSPT have different degree of taper. If you use NPT male into BSPT female, it will seal by 1-2 thread depth instead of 3-4 thread depth if you use the matching thread type. That being said, the online community as a whole is in agreement that you can screw in NPT male into BSPT female, but not the other way around.

good news is that if you have Japanese gauge such as defi, it comes with 1/8" PT or BSPT (which is the same thing). It will directly bolt onto the rear iron without adapter. Spacing is another issue I guess. I think I would need a spacer anyway to fit the sensor on there. Will report back this weekend.