Air/Fuel Ratios + O2 sensors, Perfection Options

[Consynx]

How is something like a desired air/fuel ratio calculated?

the way a stock ecu determined lean/rich is just a factor of More/Less, but a wideband gives you the actual numbers. I'm curious how these numbers can be determined.

ex, a 3s-gte runs _ for a stock air/fuel, but a 5s-fte runs ~12(looking @ manny's tuning)

does the air/fuel ratio take into account the increased air-pressure?

basically just looking for any info you have on these ratios...the book i'm reading kinda skimmed the top of it all

edit:
also, just making sure my logic is correct.
a stock O2 sensor goes after the combustion chamber, but if turbo also after the air is brought back to regular pressure....
a stock o2 sensor just reads rich/lean and the ecu adjusts accordingly
a wideband O2 sensor goes in the same place, but has a different fitting.
It on the other hand reads a value. instead of rich/lean it gives the #'s we are talking about.

This post has been edited by Consynx: Aug 8, 2005 - 11:18 AM

[presure2]

steve, in most cases, a stock 3s runs REAL rich. around 10:1 or so especially in the higher rpms..
its made to be real rich like that cause rich = safe, even if you loose a couple HP.
ideally you'd wanna see it around 11.5-12:1 on a turbo car.
some say 12.5:1 is still safe, but i like to personally stay a little more on the safe side.
basicly leaner = more power/ closer to detonation
richer = safer...up to a point..then its just a waste.