What's going on here then? Exhaust gas in my face!

[mikeonb4c]

Quite low concentrations could I fear be very significant in human terms. I'm an ex- biochemist so can remember (I hope!) a little. Haemoglobin in the blood bonds with oxygen, which is then transported from the lungs around the body and taken up by those parts needing oxygen (e.g. muscle, brain, nerves, everywhere really). Carbon monoxide has the unfortunate ability to bond with haemogloblin on those receptor sites intended for oxygen. Once bonded, and unlike oxygen, it is not released. So that receptor site on that haemoglobin molecule is no longer available for proper use. Because of that, CO poisoning is pretty much cumulative, and becuase of that relatively low concentrations are dangerous. On Wikopedia at http://en.wikipedia.org/wiki/Carbon_monoxide_detector I see a detector device is set to trigger at 400 parts per million. I'm not good at maths but I think that means the Citroen is safe (but as implied above there is no room for complacency).

Diesels aren't great overall e.g. (from the web)

The gases in diesel exhaust can also create health problems. The top
eight are listed here:

nitrous oxide
nitrogen dioxide
formaldehyde
benzene
sulfur dioxide
hydrogen sulfide
carbon dioxide
carbon monoxide.

We could use a cheap 'car fume' detector. I wonder if there is such a thing. Must have a look

[scanner]

That's not in the correct order of magnitude though and I think you'll find that list is when running on very old standard, very sulphury diesel (as used in the US where most of the anti-diesel propaganda comes from) not very "clean" USLD.
On UK standard DERV benzene and CO for example are almost non-existent compared to in petrol fumes.

As I've said before neither is good but on balance the diesel "bundle" is the less immediately injurious - especially if running on veggie or Shell's V-Power (if you can afford it).

Could we have the same list for petrols now?

And for the first 15miles before the cat warms up properly and starts working.

[haydn callow]

not another "beeping" sensor

[helen&tony]

Hi Mike
You're right about the haemoglobin/ CO. In fact , the reason CO is so dangerous is that the blood absorbs CO in preference to oxygen..... five times more preferentially, and as you already know, it is colourless and odourless, and as such is an insidious killer.
Helen

[mikeonb4c]

Scanner - apologies, I'm not trying to be a petrolhead. Petrol is indisputably nastier, which is why I didn't put up details on it, but it's a bit like saying that smoking 60 a day is not as bad as a bottle of Scotch. It's a non argument really.

And hey, I'm a dieselhead - why would I knock it

PS - the one I'm waiting for bad news to break on is the catalyser. Unless my nostrils are deceivng me, my body is not at all happy about breathing in fumes from a catalysed exhaust when the engine is cold. Anyone know the science behind that?

H&T - yes, should have stressed, its because CO totally overwhelms oxygen in it's affinity for haemoglobin. V nasty stuff.

[dandywarhol]

Saves me a thousand words

http://auto.howstuffworks.com/catalytic-converter.htm

Brill website

[scanner]

Saves me a thousand words

http://auto.howstuffworks.com/catalytic-converter.htm

Brill website

Yep I know all that....

Why it's needed, how it works etc.

But this

One of its biggest shortcomings is that it only works at a fairly high temperature. When you start your car cold, the catalytic converter does almost nothing to reduce the pollution in your exhaust.

is the most important bit so far as use in normal UK conditions. Test have shown that it takes between 5 and 15 miles depending on driving and weather conditions for the cat to reach anything near working temperature and until then, due to the adjustments needed for the engine to operate with a cat fitted, most petrol engine pump out more pollutants.

Now guess into which mileage band the average UK car journeys falls?

Less than 5 miles, so that means the average car journey is undertaken with a cat that is not up to correct working temperature.

They were not designed for a cold wet UK they were designed (originally) for a hot dry Los Angeles.

Take your car in for an emissions test and leave it overnight before testing it as soon as it is started the next morning. It won't be 0.01% CO then.

[dandywarhol]

Yep - totally agree, the lamda sensor did it's best to keep it to 0.5% cold...............I just thought I'd chuck in the Citroen bit to liven up the discussion

[scanner]

Yep - totally agree, the lamda sensor did it's best to keep it to 0.5% cold...............I just thought I'd chuck in the Citroen bit to liven up the discussion

But you missed out the magic 2CV bit...............................

[dandywarhol]

...............now that WAS a car I had a bit of fun with a friend's endurance racing 2CV a few years back - a right hoot outcornering EVERYTHING in it's wake on oversized 135/15s

[mikeonb4c]

Saves me a thousand words

http://auto.howstuffworks.com/catalytic-converter.htm

Brill website

Oh crap - haven't got time to read all that. I was aware that cat converters didn't do good work until warmed up. But it's the 'metallic' smell that really makes me curious as it's that that my nostrils are saying is a new and strange poison - what is it

[scanner]

...............now that WAS a car I had a bit of fun with a friend's endurance racing 2CV a few years back - a right hoot outcornering EVERYTHING in it's wake on oversized 135/15s

Don't let BDC hear you say that.

http://www.igmaynard.co.uk/bongo/forum/ ... sc&start=0