Air/fuel Ratios on a NA
 

So, I finally hooked up an O2 sensor, and decided to take a look at the readings. After letting the car warm up I took her for a spin.

I noted that most of the time my reading was .85 Volts or higher (never above .91). There was a brief time at around 3k (till about 3500 right before the secondaries kick in) I had in the .68v to .72v range.

Idle was around .85, though after hard driving an then sitting still I would see .9v for a while then it drops to the high .8v again


I have a NA, with a pretty free flowing exhaust, intake porting, TB mod, CAI and I Premix. Should I think about a SAFC II to adjust things around a bit? If I have read other threads correctly .85v represents 14.7/1 A/F ratio right? Anyway, just looking for opinions. I will be taking more readings for the next week or so to get a better feel of how the car normally operates.

No, a 14.7:1 AFR would give 0.4-0.6V. You should see above that under acceleration, a reading flickering back and forth over 0.5V under light-load cruise, and no reading when you lift off the gas. If you're really worried about mixtures goet to a dyno before shelling out money on more mods.

not really worried, just wondering. The car runs fine really. I guess I am running very rich then, from my numbers right?


And yes, on deceleration stuff drops to zero.

Do you have a set of voltage mappings to A/F ratios?

I understand the the narrow band O2 Sensor is really only good for reading values around stoic, but I should be able to tell if the car is running way too rich, or too lean.


Edit: I think I may have found an answer to my question. Does this graph look right to you?
http://hp.autometer.com/techtips/faq.../air_fuel.html

It matches up with your ~.4v number for stoic...

Anybody else??