a/f compared to emissions testing question

[StangLou]

Milenko's post a few threads down about his emissions testing sparked a thought in my head.
As long as you have done a dyno and your a/f is ok, and you are running a safe tune wouldnt it make sense that your going to pass emissions or am I way off here. I know you have to take into effect that fact that some states dont allow L/T's and some states are picky on having cats and the # of cats you have to have. Im just talking stricktly about the a/f though. If Im way off someone correct me.
Doesnt the emissions testing take into account ppm of CO2? What exactly is the a/f on the dyno testing? I am assuming it is testing ppm of something. I would expect if you have a ton of fuel that is showing in your a/f reading that you would fail emissions testing. If you have a "normal/safe" a/f tune on shouldnt everything check out A OK???
Just something I wanted to scratch my head to, again if Im way off somoene let me know

 

[ADRENLN]

good question......bump!

 

[HIGDON]

I would have to say that a properly tuned vehicle with a steady and clean a/f, as close to stoichiometric as possible, would pass emissions. Most tests use a 5 gas machine that measures O, NOx,CO, CO2, and HC. No matter how you tune you will never get the engine to run perfectly clean. If you got a hot motor running a good tune the only thing I would worry about would be CO2 as a more complete combustion will lower your HC's and CO and increase the CO2. CO2 numbers help show a complete combustion yet, and this is what I don't get, they can't be too high because they are considered a "greenhouse" gas. NOx generally goes through the roof when you are running lean and there's a lot more heat and pressure in the combustion chambers. Oxygen is used to determine your vehicles catalytic converters efficiency. Not sure if I helped clear up you question But this is just a bit of stuff I thought would help this discussion along

 

[StangLou]

I just noticed a ton of these L/T, Non catted, will I pass emissions threads in the last week or so. Figured I would ask my own . Your answer helps some and it goes along with my train of thought As long as you have what is needed to pass your states visual exam, a nice a/f ratio should give you a very good idea as to if you can pass emissions or not. Im not saying its anywhere near 100% accurate, thats why I wanted to open up a discussion on it.