I want to replace the oil pressure switch on an EJ20 engine with a sender, and use the computer to log oil pressure, and turn the oil pressure warning light on at varying pressure depending on RPM. (You know, like VW did way back in the 80s)
I had thought/assumed that the switch was M10x1, but noooo.... it is BSP because of course a Japanese car would use a weird British thread.
Can anyone think of a fairly low profile 1/8 BSP sender?
I have quite a few RX-7 senders, which unfortunately are all bad, and new ones are so hideously expensive that of the two RX-7s I have, neither has a working factory oil pressure gauge. They are also huge and one-wire, I'd prefer a three wire unit.
Would part # AM 2269 from Pegasus Racing help? Its an adapter from BSP to NPT.
IIRC BSP is like 1 thread per inch different than NPT
I know this will make some folks recoil in horror, but my experience has been that if you run an 1/8"-27 NPT tap through those 1/8"-28 BSP threads, the resulting NPT threads will seal just fine. Then you can run one of the cheapo Chinese 0-100 psi stainless 3-wire senders from eBay.
Or do it right and get one of the adapters. I've done it both ways depending on the situation, and both ways have worked for me.
I think Link used to (still might? Havent looked in ages) make a 3 wire one. It was pretty pricey, though. About $200, I want to say.
Otherwise, everybody just runs adapters. I've always thought it odd, as there are a metric ton of engines that run 1/8BSPT threads, but nobody I'm aware of, outside of Link, makes a good 3 wire sensor.
Definitely have just run the NPT tap and used some rtv with good results.
I was hoping for something RockAuto-able that I could look up the pressure/resistance curve. Three wire because I already have three unused sensors on the intake manifold that have 5vref/sensor ground right there.
I remember my '88 Subaru had a gauge, sender is still available, is fairly cheap, BUT one wire and unsure about resistance curve. And I don't think it will fit.
All the pressure sensors that I have access to are NPT or MXX with a crush washer with a few with MXX and tapered seal at the tip (like an AN fitting) but usually for very high pressure like DI fuel sensors.
I think Harley uses a 1/8 npt fitting on the oil pressure warning switch, but I think the switch is like 5psi or something stupid low. One wire.
In reply to Paul_VR6 (Forum Supporter) :
It's weird, isn't it.
I actually had the perfect sending unit in M10x1.0 with a washer, but no.
I do not think there is room, but I have a whole lot of Chrysler oil pressure senders. Every 3.6 oil cooler comes with them, so I have a lot of used ones 
They look NPT though.
1/8 bspt male to m10x1 female adapter? for the Skyline I got a 1/8 bspt male to 1/8 bspt and 1/8 npt male tee to add my aftermarket sender.
https://www.ebay.com/itm/201959857209
Can you mount it remotely? Like get a hose and mount the sensor at the end? Might help with the space issue.
There is VERY little room in this engine bay, plus I have a healthy respect/fear of any kind of external oil line. Pressurized fluids want to be free!
It feels absolutely bitter cold so I did not get any work done this evening, but what I DID do is a little research at work, and some test assembly of the Subaru engine to see just how much room there isn't.
Here is the switch (boo, hiss)
It does not thread into the engine block/case like I had remembered, but into a fitting, which is apparently 18x1.5.
With the accessories on and the alternator all the way down, which it may need to be for hood clearance:
This may work, I have an idea.
M18x1.5 makes one think of oxygen sensor bung plugs, and I have a ton of those, but they are all internal hex. You know what is external hex, low profile, and M18x1.5? Mazda smoothcase transmission drain plugs. I still have about half a dozen dead smoothcases kicking around...
Adapter. Just Google it and you'll get a zillion hits. Everyone who's ever tried to put an oil sender on a '90s Asian car knows the pain...
