Been thinking about the high NOx emissions from the Golf petrol.
It will be an early catalyst equipped car. The catalyst should convert CO into CO2 and the NOx into Nitrogen and use the freed-up Oxygen to combine with the CO to give the CO2.
Sadly, at MOT, NOx is not measured. I believe to measure it requires significantly more expnsive machines than the current CO and HC tests. So we don't know how much NOx actually escapes 'not converted'.
I'm thinking that perhaps his catalyst is not as good as it was when new. Newer petrol cars are likely to be much better on NOx.
Diesel produces NOx, but we can't fit a catalyst to them, as they'd last a very short time, contaminated with the soot.
Many years ago, Volvo challenged the California legislature when they proposed more stringent emission regulations, and proved that already what was coming out of a Volvo exhaust was cleaner than that going in. They won, but I can't remember any detail. And can't be bothered to go search it out.
Another story, I think it was Captain Cook, or another famous explorer in a wooden sailing ship, that recorded in his log, when approaching San Francisco, that the area was shrouded in a thick yellow fog. Perhaps not then caused by vehicle exhausts. Although, to be fair, having later invented the internal combustion engine, we may have contributed to the problem.
