[Diy_efi] What is stoichometric....really?

[Mike]

At 06:32 PM 14/10/2002 +1000, you wrote:
>Nearly all cars cruise the freeways at this A/F ratio and are
>considered to be in "Lean Burn Mode" The catalytic converter
>has very little work at these A/F ratio.

No - not at all !

It has to deal with NOx - this is the main reason for its
existence, its not just to get rid of (some) left over HC's or CO
its to handle the NOx reduction and to reduce the odd amount
of SOx as well if your fuel is bad - of course it does reduce
HC's and CO but on a scale of percentage its far more than
50% required to handle NOx emissions, Here in Australia we
have some bad sulphur fuels and you can smell the sulphur
reduced by a working CAT, whereas a car without a CAT has
a worse exhaust smell as elemental Sulphur is not nearly as
dangerous as SOx - in fact it used to be used as an antiseptic/
antibiotic during the world wars. 

Also be going leaner you are raising the combustion temperature
and this generates more NOx, in fact the reduction of NOx causes
heat to be released by the CAT - too lean and you will damage
your CAT far more then running too rich. ie. N2 + O2 to NOx is
an endothermic process whilst the opposite is exothermic, so dont
run too lean if you value your grandchildren's ability to renovate
your existing waterfront property without needing a scuba tank ;-)

rgds

mike

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