Which Oxygen Sensor?
 

Hi,

I need to replace the o2 sensor on my '80 SC Targa. Two choices:

Porsche OEM, which includes the grommet and connector for $143
Bosch for $27.50 which has a short wire with a crimp connector

That's a big difference in price, but I do wonder about the overall performance and longevity of the one with the crimp connector. Any thoughts?

Thanks, Todd

why do you even use it ..do you have to have a smog in Oregon? The car will run perfect without it.Are you using Catalist?

Ivan

"If" your ECU runs flawlessly, keep using it as you won't loose any performance.

Here you can see the correct setup:
https://nineelevenheaven.wordpress.com/the-911-sc-3-0-engine-with-catalyst-and-lambda-control/
Just get an universal BOSCH heated lambda narrowband sensor 0 258 986 502.
the two white wires will be connected to GND and switched 12v (best would be using a relay driven by the same 12v as the WUR, as then the sensor heater only gets power if engine is running.
The black wire will be connected to the wire of the OX-Sensor plug (crimped, not soldered).

Andrew,

This is a timely thread.....

I need the narrow band O2 sensor for my 1982 911sc lambda with SSI installed. 0 258 986 502 is not available in the US.

Is there a cross reference sensor you can recommend that is available in the US?

(I could never get the single wire O2 sensor to work in my SSI set up.)

Thanks.

Dave

Hi Dave, you need a 3 wire BOSCH compliant Universal Sensor -> compatible with the 3.2 Carrera.

So Andrew ,you are saying by unpluging the Oxy sensor you lose performance? Somehow i do not think so.Many 911 SC run without the oxy sensor and they do run perfect.With the oxy sensor you are looseing power,it was mainly designed for smog inspections in certain states...
Ivan

Ivan

No - I said clearly with using the ECU running flawlessly he won’t loose any performce. You simply interprete my words in another way.

And with the lambda system deactivated and running in open loop mode they run ok, but in terms of combustion and efficiency they do not run „perfect“ as perfect means optimum. There’s only one non optimal thing with the original ECU : with closed loop control and lambda regulation active, on high load the ECU enriches from approx 40-50% in stoich resulting duty cycle to 65% duty cycle where in some cases this is not resulting in lambda 0.85 for optimum performance. But honestly this is also the case when choosing your approach. As with a disconnected sensor and therefore with open loop mode, on high engine load it behaves exactly the same, as here also it switches to static 65% duty cycle. Means exactly same enrichment.

Sure on lambda based k-jet setups where sensor or anything else related is not working correctly, this will result in less power, where then deactivating the system gives a better performance. But it’s not the optimal solution.

All is explained in the article „lambda control“ on my website above.
https://nineelevenheaven.wordpress.com/the-lambda-control-of-the-911-sc/

Thanx Andrew for all technical explanation --but i will stick with mine....no CAT no OXY engine will run perfect..no need for all this lambda stuff;-)Back in the 1980`s and 90`s we had no AFR or other stuf you boys are using nowadays..All the cars ran perfect and even past the ridiculous smogs test in CA..i`m sure all the new digi stuff is very good ..but does it help you when you want to set up Carburators..i do it by feel and my hearing the engine..
Back in the 1970`s in Czechoslovakia we use to set the fuel mix like this , lighting a match behind the muffler tip if the flame went in too lean if it went out too rich...you adjusted the Skoda engines like that;-)
Again i admire your technical knowlidge...i leave at that;-)))

Ivan

I see we just have different interpretations on what means „running perfect“, but as you said we leave it at that and … have a beer. :-)

I would use the Porsche part. Make sure you inspect the plastic male end at your car that the sensor plugs into - most of them crumble or fall apart and to replace that end is really difficult because of the shielded wire that is used at that end.

Porsche is just a re seller of such parts, ... at the end most of the providers and selling brands get those Sensors from the same Supplier/manufacturer.

Thanks everyone for the responses - sorry it's taken me a couple of days to come back.

To respond to Ivan - yes, in Oregon, we have to pass smog (actually, just did in July), so I do need to keep the cat in place.

aoncurly - I don't remember who it was, but someone on here had created (printed?) a new version of the male end of the sensor, and I bought two from him (one as a backup for the future) a few years ago, so I'm good there.

I think before I had purchased the cheaper version, and I'm just questioning the crimping version (cheaper) vs. the more expensive Porsche version that has a single wire, including the grommet to go through the tin and the female end that plugs into the male receptacle in the engine bay.

I appreciate everyone's input!

I am contemplating spicing wires to plug sockets on my M3 oxy sensors.. any reason you specified crimped not soldered? Heat -risk?

The ones without the OEM clips are about $100 cheaper the M3 has 4(!) oxy sensors..

I'm curious to read the explanation for this. I've read some weird theories about the reference air being measured through the wire strands hence needing to be not soldered but crimped to preserve wire strands. :confused:

But I've also read that this is kind of urban legend. And the O2 sensor wire is soldered inside the ECU anyway.

So, BS or real technical justification?

Yes, makes sense that it has something to do with the resistance of the wires and a blob of solder would change that resistance.

Chat GPT gives a perfect answer and it’s English is far better than mine :-) :

Question:
Why should the wires of an ox sensor of a car being crimped and not being soldered? Something to do with reference air throughout the wire?

Answer:
Yes, the reason is not about normal electrical conductivity, but about the oxygen sensor’s design and how it “breathes.”

⸻

🔑 Key points
1. Most zirconia O₂ sensors need a reference to outside air.
• A narrowband or wideband oxygen sensor compares the oxygen in the exhaust with oxygen from outside air.
• Many sensors draw that reference air through the wire insulation and the crimped terminals, not through a visible vent hole.
2. The wire and terminal are designed to be slightly gas-permeable.
• The sensor’s lead wires are usually special “porous” or “vented” insulation.
• The factory crimp connection keeps electrical contact but still allows a small path for air diffusion.
3. Solder blocks the air path and can damage the sensor.
• When you solder, molten solder wicks up the strands and seals the conductor, stopping air flow.
• Heat from soldering can also damage the wire’s gas-permeable insulation and wick flux or solder inside, ruining the tiny vent path.
4. Crimping avoids heat and keeps the designed micro-vent.
• Proper OEM-style crimp terminals keep the mechanical and electrical connection while leaving the tiny air diffusion path intact.
• That’s why all sensor makers (Bosch, Denso, NTK, etc.) say: don’t solder O₂ sensor wires.

⸻

🚗 Bottom line
• Crimp = good → keeps the oxygen sensor’s reference air path and proper electrical connection.
• Solder = bad → can seal the vent path, overheat or contaminate the sensor lead, and cause inaccurate readings or premature failure.

If you must repair an O₂ sensor harness, use proper crimp butt connectors or OEM pigtails (sometimes with heat-shrink that still lets the wire breathe).

I have changed my O2 sensor several times. Always use a butt crimp. But I have been
using generic heat-shrink over the crimp for several inches either side to tidy it up.

Is there a special type of heat shrink required? Or is no heat shrink better?

Thanks Andrew

Just don’t let it shrink all the way down until it seals everything.

"• Many sensors draw that reference air through the wire insulation and the crimped terminals, not through a visible vent hole.
2. The wire and terminal are designed to be slightly gas-permeable.
• The sensor’s lead wires are usually special “porous” or “vented” insulation."
...having in the past worked as an occasional electrician, mostly household factory installs,
I find this information to be astoundingly hard to believe. Shocking even !
I don't know if I should simply stand corrected or if I need to be skeptical of Chat GPT or do more research. The oxygen sensor wires are heat-shielded with a woven tube of fabric and they are about 1/2" (-2 cm) away from the exhaust pipe ( on my BMW M3 ) these wires have one job to transfer electric signals, never considered them having to breathe or to send air through the strands...but I get it: there is a difference between a crimped wire and a soldered wire.
Do wires breathe? Not that i know of, but I know they can drown.. ie they generally don't do 'great ' submerged in liquid.