S40 V40 Parts: S40 P1 Oxygen sensor PO141/Lambda sensor

[canis]

I think this is a myth.

When copper wires are manufactured, they are stretched through a series of rollers, each pair faster than the preceeding pair. In order for the grip on the wire to be sufficient, the insulation and copper become clamped, and it's why recovering the copper from flex is so much harder than solid cores - the plastic insulation is squished into the crevices of the copper strands. The obvious experiment is to try blowing down one end. I'm not going to try it, because I think I can predict it will be impossible.

If a sensor needed a reference air source, it could more easily be obtained from a port in it's casing, which is in open air, after all. Drawing reference air from inside the car, especially under the carpet, especially after the bacterial action on dead skin, spilt coffee, dropped toffees, would be silly as it wouldn't be an accurate source of ambiant oxygen available from the external environment, which is the source of oxygen the sensor is measuring to do the job of monitoring combustion mixtures.

Should a sensor absolutely demand air from inside the cabin, the most obvious and practicable solution would be a pipe. The wires could be run inside the pipe to offer them protection. The pipe would need to be air-tight. All images of sensors, and the ones I've seen myself, are not like this. The outer sheath typically is shorter than the overall wire length, and the number of wires to the sensor can be easily seen - indeed, counting them is an important factor when identifying their type.

Modern cars are littered with breather tubes. Rear axled cars even vent evaporative gases from their differentials via a tube the entire length of the car, to burn them off. That's a lot to do for the puny amount of hydrocarbon the EP90 will produce, but that's the level of seriousness. Same with petrol tanks, which used to simply vent into the open air, now are carried to the front bumper and collected in a charcoal canister to be burned later. With all this breather pipe business going on, running a tube to the sensor would be child's play. Venting through copper strands becomes an increasingly farfetched notion.

I've just read this page , and I've no reason to doubt NGK's authority on the matter, and nowhere is reference air mentioned, save for one line which reads thus:

The inside of the thimble is hollow and is used to hold ambient air as a reference gas.

The impracticality of supplying this hollow with air sucked (how?) through electrical flex under the insulation is simply too farfetched.

So unless someone can find factual evidence, I'm calling this busted.

You're welcome

[canis]

Sorry for double-posting. Virgin-on-the-ridiculous-media at their best.

[oliverpervasive]

I have screwed in the ebay item from a v40 1.8 sports which has the Volvo code as per the replacement part for the obsolete one ( see earlier)
Its ticking over as if hunting a bit - but its not been run for a week and is jacked up - I'm going to secure all the bits and take it for a run.

Question : will the engine light go out if it is now all OK - or will I need to reset it to clear codes?
I don't have vol- fcr so its a trip right over London to borrow from Bigfella.

I think I could disconnect the negative battery lead - but I don't have the radio code ( its not written on it)

[bobthecabbage]

The older sensors did draw their reference air from a hole in the sensor.

This has obvious drawbacks due to being liable to contamination/blocking.

Bosch (and probably others to be honest) draw their air from the wiring harness.

Oxygen is a very small molecule in the order of 0.000000293 millimetres or 293 picometres. Therefore it is not too much of a stretch to imagine that they can fit down between the conductors or between the conductors and the insulation of a wire. If you imagine the the gap between stands of the conductors might be 100th of a millimetre so 0.01 millimetres then 34129 oxygen molecules could fit side by side down that gap and if you imagine that gap to be circular then that would be 914860002 oxygen molecules.

So that is nearly 1 billion oxygen molecules per gap of which I guess there could be 30 or 40 gaps depending on how many strands in the conductor. Then you would need to add the gap between the conductor and the insulation which would probably double that value and then multiply that by the number of wires. So I reckon we could easily be looking at 200 billion oxygen molecules. That is in a slice of cable one oxygen molecule thick.

If we say that air is only 20% (actually 21% I think) oxygen by volume then reduces us to 40 billion oxygen molecules.

If we then say that the wire is 500 millimetres long we get 68259385665529010238 oxygen molecules present in the wires.

As oxygen is very small then the molecules in the wires can probably be replaced through diffusion through the insulation itself as well as by bypassing the seals on any connectors.

Obviously the consumption of oxygen is so small that this system provides an adequate supply to replenish any oxygen consumed by the process.

Forgot to add this link to video where bosch say their connector lets the air in.

https://youtu.be/u3OWEB_6GBc

[oliverpervasive]

After a cruise through the streets of Hounslow I am pleased to report my engine warning light has gone out. No need for reset or battery unplug.
So the replacement o2 sensor from the v40 sport worked- Yippee/sound of beer being opened!

I will splice the old one but will put it in the spare parts pile in case I never need it.

Thanks for all the inputs/tips and theoretical discussions as to how the sensors actually sense!

Now to find the radio code.....

OP

[druid]

Originally Posted by bobthecabbage

The older sensors did draw their reference air from a hole in the sensor.

This has obvious drawbacks due to being liable to contamination/blocking.

Bosch (and probably others to be honest) draw their air from the wiring harness.

Oxygen is a very small molecule in the order of 0.000000293 millimetres or 293 picometres. Therefore it is not too much of a stretch to imagine that they can fit down between the conductors or between the conductors and the insulation of a wire. If you imagine the the gap between stands of the conductors might be 100th of a millimetre so 0.01 millimetres then 34129 oxygen molecules could fit side by side down that gap and if you imagine that gap to be circular then that would be 914860002 oxygen molecules.

So that is nearly 1 billion oxygen molecules per gap of which I guess there could be 30 or 40 gaps depending on how many strands in the conductor. Then you would need to add the gap between the conductor and the insulation which would probably double that value and then multiply that by the number of wires. So I reckon we could easily be looking at 200 billion oxygen molecules. That is in a slice of cable one oxygen molecule thick.

If we say that air is only 20% (actually 21% I think) oxygen by volume then reduces us to 40 billion oxygen molecules.

If we then say that the wire is 500 millimetres long we get 68259385665529010238 oxygen molecules present in the wires.

As oxygen is very small then the molecules in the wires can probably be replaced through diffusion through the insulation itself as well as by bypassing the seals on any connectors.

Obviously the consumption of oxygen is so small that this system provides an adequate supply to replenish any oxygen consumed by the process.

Forgot to add this link to video where bosch say their connector lets the air in.

https://youtu.be/u3OWEB_6GBc

Stop using science, it confuses people

[canis]

Originally Posted by bobthecabbage

Bosch (and probably others to be honest) draw their air from the wiring harness...

Thanks for going to so much trouble, I guess I'll just have to take your word for it. I'm not 100% convinced. Points have been missed, questions still remain, and the film doesn't say very much, and the accompanying animation is somewhat ambiguous. Nevertheless I am indebted to you for taking the time to explain so thoroughly.

[bobthecabbage]

I can't find an electron microscope picture of a wire in cross section but I found this diagram.

http://www.12voltplanet.co.uk/user/S...core_cable.png

Basically what I'm saying is that as the conductors are round and therefore cannot stack neatly together without leaving gaps, then as far as oxygen is concerned you have in effect a 40 billion lane motorway down which oxygen molecules can travel.

In which case you would be surprised if oxygen couldn't get down the wire!

This bosch data sheet also mentions

The sensor receives the reference air
through the connection cable. This means
that the connector must be clean and dry.
Contact spray, and anti-corrosion agents
etc. are forbidden.
– The connection cable must not be
soldered. It must only be crimped,
clamped, or secured by screws.

http://luniks.net/lambda/sheets/sensors_oxygenlsm11.pdf

It seems that some sensors get their reference air through a ptfe membrane (think goretex) in the back of the sensor (denso), some get it via the wires (bosch) and some don't require an external air reference (titania type).

I didn't believe it the first time I read it but on a microscopic level you can see how it is easily possible. I do wonder if it was discovered by accident when someone forgot to leave a reference hole in an early prototype?

[canis]

Originally Posted by bobthecabbage

Basically what I'm saying is that as the conductors are round and therefore cannot stack neatly together without leaving gaps, then as far as oxygen is concerned you have in effect a 40 billion lane motorway down which oxygen molecules can travel.

True enough. Dunno if the wires are made a different way (let's face it, there's any number of cabling standards) but removing the copper from old flex is notoriously difficult because it squishes into the gaps during manufacture.

Certainly, circles don't tesselate. I heard from a college lecturer the cables on pilons have a gap in the middle of the conductors, into which they later installed optic fibre for data transmission. Dunno how true the story is, I just found it interesting and never forgot it.

Originally Posted by bobthecabbage

This bosch data sheet also mentions
<snip>
It seems that some sensors get their reference air through a ptfe membrane (think goretex) in the back of the sensor (denso), some get it via the wires (bosch) and some don't require an external air reference (titania type).

I didn't believe it the first time I read it but on a microscopic level you can see how it is easily possible. I do wonder if it was discovered by accident when someone forgot to leave a reference hole in an early prototype?

Well. Can't argue with the datasheet. Once again, I'm much obliged. Thank you.

[bobthecabbage]

They are replacing the pylon cables that go past my house. I didn't know they were hollow but I remember seeing other large gauge cables that were.

Many years ago they installed a fibre optic cable by wrapping it round the top wire (which is a ground cable and therefore not live). They must have scrapped that as they had to cut it at each pylon.

Maybe they have replaced it with a cable in cable set-up? I suspect that it may have been redundant now anyway as bt fibre has made it to the area although not to my house.