I have a non-stock exhaust, that drops straight down and then goes under the transmission to head backwards on the right-hand side.
Getting to the inside of the three nuts that hold that to the exhaust header is incredibly annoying.
This is mostly a complaint. I designed the exhaust poorly. But, wow, think about bolt access when you build new stuff. I wish I'd stayed with the A12 two-bolt exhaust.

However, the question part: where would you put an oxygen sensor?
I know in the A15E it was formed into the cast iron header itself.
I don't have one of those, and unless I braze, it's hard to get a port welded into cast iron.
So I'd like to put it right below the header, in the steel exhaust pipe.
Here's the problem: with the A14 (and all the non-fuel-injected cars)the joint between the exhaust and the header is a steel on steel joint, and it may leak. If it's leaking, the sensor isn't going to be accurate.
It looks like on the fuel injected models they used two flat plates with a sealing gasket.
What would you do?
I suppose I could machine a thin foil-ish copper gasket that I stuck on the joint and compressed with the three bolts to get a compliant seal.
My exhaust pipe hangs low and regularly hits the ground, so I'm doubtful that would last very long.

This might be more difficult than I thought it was going to be...

I installed mine just past where the header bolts to the exhaust. As my set up is strictly for an air fuel gauge it doesn't much matter if it's off a bit.

I would think you'd want it in the collector area.

You should be able to get an exhaust gasket for a 3 bolt flange? You could try the Copper gasket and sensor friendly copper sealant ?
Is there no room above the flange to weld in a sensor bung above horizontal?
dp

Yeah, I'm looking at just below the joint. (But low enough I can get the clamping collar for the joint down past the screws, obviously.)

I'll look for a copper seal/gasket: I hadn't yet found one available.

Zigmondo: there is room above the gasket but I have a cast iron header. (Haven't yet made my own.) That'd be a perfect place to put it but I can't weld cast iron. I've brazed steel to cast iron before but this definitely needs to be airtight, and I'm not confident of my ability to manage that.

Thanks!

Sorry 'Smells' I misunderstood when you said you had a "non stock exhaust" I immediately thought
headers as well when you mention cast headers on an A15E "but I dont have one of those ".
It's bit hard to picture the actual issue without a photo - is that possible ?
I wouldn't be too woried about putting it after the join, if thats the only position available, as some tuners use a 'sniffer' O2 sensor which is just an O2 sensor shoved up the tailpipe. Just has to be mounted above the horizontal ( I think its to avoid condensation contamination )
Permatex ULTRA copper is sensor safe

https://www.mxstore.com.au/p/Permatex- ... PonKoZ68nopsaAs1pEALw_wcB