A/F Ratio Gauge - Quick Ques.

[DjLiquid]

I've been reading that people don't like the autometer A/F ratio gauge cause it's too sensitive and will almost always read rich. Well, I have a SAFC-II and was wondering if it will tell me my A/F ratio on there. At the moment I don't have either hooked up

[fanta]

Essentially worthless.

[81na ZX]

Its not the gauge thats bad, its the idea.Narrow band O2 sensors are just about worthless for reliably tuning.Heres a good picture[quote=""MegaSquirt""]With a narrow band sensor, we can really only tell for certain whether we are rich or lean, but not by how much. If you look at the graph, you can see that for a narrow band sensor, the 12.5:1 AFR required for maximum power can give O2 voltage from 0.8 to 0.95 (depending on exhaust gas temperature), yet this same range of O2 voltages can indicate mixtures from 10:1 to 14.5:1. So we cannot use it reliably to set mixtures for full power. With a wide-band sensor, 12.5:1 corresponds to 2.08 volts, and 2.08 volts means 12.5:1. Thus there is no ambiguity over AFR and voltages.[/quote]

[float_6969]

A narrow band isn't good for maximum power tuning. What it WILL tell you is if are lean or rich, which is important. You can use one to at least get the car running so that you can drive it to a dyno to get it accuratly tuned. That's what I'm going to do anyway....

[Coldspawn]

A narrow band isn't good for maximum power tuning. What it WILL tell you is if are lean or rich, which is important.

It matters what you think is rich or lean. All a narrow band 02 sesnor can do it is tell you where the stoichiometric ratio (14.7 on gas) is at. Like 81na ZX, everything is "blind" to the sensor. All the stoichiometric ratio is, is the ratio where the least exhaust gas are made at. This does not mean you will get the best MPG on the stoichiometric ratio, a leaner mixture will net you more MPG. A chart to make it clearer. To tune with a narrow band, you have to cross over .450V (back and forth) untill the corrections at close to nothing or at .450 perfectly.

You can use one to at least get the car running so that you can drive it to a dyno to get it accuratly tuned. That's what I'm going to do anyway....

Non-eddy curcuit dynos (dynojet, inertial dynos) can not tune partial throttle correctly (they can not hold a RPM for you, well, good enough for tuning). You need a wideband to tune a street car properly in partial throttle. Only dynoing WOT maps, you are only seeing 25% (depnding on the res. of the map, it is less then that most of the time). Not to mention that older nissans have a non-heated 02, so you have to wait a good bit for a correct reading.