O2 voltages

[Bernd Felsche]

Byron Smith tapped away at the keyboard with:
> So, production cars with wide band O2 still cycle about
> stoich for the converter's sake?  Do they at least have a
> much tighter cycle?  Or are other changes made that make
> cycling about stoich unnecessary?

You still need an excess of CO to convert NOx; hence the need to run
rich occasionally. Cars with a specialised storage cat (for the NOx)
need only be cycled very occasionally. The engine management system
does have to deal with the temporary torque increase from running
lean which can be done by a combination of throttle, ignition timing
and EGR. (e.g. Bosch Motronic for direct injection gasoline engines;
MED-7)

Using EGR to control exhaust gas temperature in lean-burn manages
NOx emissions so that the need to run rich is greatly reduced.
Closed-loop control on the NOx storage cat determines when a "purge"
cycle is necessary.

-- 
Bernd Felsche - Innovative Reckoning
Perth, Western Australia
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