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As this regulating process is so important, uncontrolled catalytic converters can only clean about 45% of the exhaust fumes, whereas computer controlled catalytic converter systems can clean 90-95%.
Note, you have a fine balance on tuning, especially with the NOx.Hotter Temps, More Oxygen, Advanced Timing --> better combustion, less hydrocarbons, less Carbon Monoxide.Hotter Temps, More Oxygen, Advanced Timing --> Increased NOx.So, what gives a "clean running car" for other pollutants, can be problematic with NOx, and visa-versa.
I mean if we ignore NOx as a pollutant, doesn't it in some instances actually represent an increase in mechanical efficiency when it reacts with air (at post 1200degC I believe) - ie. more expansion via a endothermic reaction.
I still don't know for sure whether an engine producing high NOx counts has a better mechanical efficiency than one with next to none - ?
Clifford,I bet your Encore was a real "babe magnet" 
A friend of mine bought a Chevrolet Chevette when he came to the US.
Quote from: CliffordK on 11/12/2010 12:05:12Note, you have a fine balance on tuning, especially with the NOx. ...So, is more mechanical work made available from N2's reacting with O2's to make NOx's ? .... blah blah blah
Note, you have a fine balance on tuning, especially with the NOx. ...
For Nitric oxide (NO), you start with dimers and end with a dimer, so you end up with no net change in moles.N2 + O2 --> 2NOBut, if instead you are making Nitrogen Dioxide (NO2), then you end up with fewer moles.N2 + 2O2 --> 2NO2 (3 moles --> 2 moles).And, thus the formation of NOx would actually reduce the energy.Assuming it is mildly endothermic, that means lower temperatures, and less energy too.Breaking down the NOx, would produce more moles of product, and more kinetic energy.
I think advancing the timing increases the time for combustion... and thus I would expect a more complete burn.
In ye olden days we had mechanical distributors that had a centripetal advance mechanism. Presumably these have been superceded by fiendishly complicated electronics
The rest of the time was spent disassembling and reassembling a load of kit that looked like it belonged more properly in a CRT type TV set
Remember that NOx is a combustion byproduct that is essentially opposite from Carbon Monoxide (CO), Hydrocarbons (HC), and Particulate Matter (PM).Think of NOx as too much oxygen, and too much combustion.CO, HC, PM, are essentially too little Oxygen, and too little combustion.Thus graphs of NOx often go opposite the others.
A quick web search indicates suggestions of advanced timing increases NOx, and retarded timing decreases it.