why do haynes specifiy CO% at 'idle'?

Oct 01, 2006 6 Replies

why is so important about the CO at idle? for most journeys the engine runs idling for only a small fraction of the time so it wouldnt be a major factor of how it runs on idle for economy or environment.



I would more have expected carbs to be calibrated & tested with CO% at



2500rpm.

or does a properly set idle mean the other speed ranges will also be at the right settings? thx



b

well it would for an SU type carb....

The message from "beerismygas" contains these words:

Because that's how it's tested at MOT.

The message from "john" contains these words:

Only if the needle isn't worn and the jet isn't worn and it's the right pair and the spindle holes haven't gone oval.

Wow, really?

I think the gist imposed by the OP was that as a car very rarely is idling, why should CO2 readings at idle be used as a benchmark at all? A range of RPM measurements could be taken to determine if CO2 output at those levels, in which the car will be used, pass.

It's measurable. At "realistic" rpms, it's just too difficult to measure it repeatably. We don't even do this for MOTs with a significant investment in test gear, so for Haynes to attempt it with maybe a 50 quid Gunson would be unrealistic.

Because it's a fairly good indicator of worst case of what it's like at other speeds, particularly on something with a CAT.

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