This isn't related to tuning per-se, but I wondered if someone who knew how these things work could answer a question i've got in relation to vehicle emissions.

I know that during part throttle cruising, the engine runs in closed loop control by the lambda probe, maintaining an exact stoichiometric fuel:air ratio. The untreated gases hit the catalyst, and the first thing that happens is that any unused O2 is used to complete oxidation of unburned hydrocarbons and carbon monoxide into CO2 and water. Once all the free O2 is gone, the catalyst strips oxygen atom off the NOx , reducing them to harmless molecular nitrogen, and uses these freed oxygen atoms to complete oxidation of the remaining CO and HC. If the mixture is a little too rich, the NOx will run out with HC and CO still left over , if too lean, the HC and CO emissions will be really good but you'll be chucking out tons of left over NOx. But the lambda probe keeps things under very tight control.

However, i have to wonder what happens to emissions under full throttle conditions and rapid transients, since that is how people drive in the real world. As far as i was aware, spark ignition engines produce optiimal power rich of stoic, in fact they may even need to run rich to avoid detonation at full throttle, due to the manufacturer wanting the compression ratio as high as possible. As for the downsized, turbo engines that are now in vogue, do they have to go even richer to avoid detonation at full boost?

What happens to the CO and HC emissions when the driver boots it?

I've heard that the catalyst has an ability to store oxygen, however, unless the lambda probe is downstream of the cat, how is the engine ECU going to know how much to lean out the engine, in order to restore the cat's oxygen levels after the full throttle excursion?

I'm just pondering this point because i'm so concerned with whether or not my diesel emits a puff of smoke when snapping the throttle open at certain points in the rev range, and because one of my work colleagues keeps making "dirty diesel" comments about my car (not tuned, euro V commonrail diesel). I'm just wondering what's coming out of the exhaust of his 10 year old focus every time he floors it to get past me on the way to work.. just because it's invisible doesn't make it harmless does it?

The enrichment increase CO emissions until lambda target is reached.
This target on full throttle is richer than stoch.
When cruising the target is near stoch.