FMXer

I found these two sites that claim to sell modified A/F gauges so they are accurate for closed loop tuning, does anyone know HOW there modifying them? So I can do it

http://store.yahoo.com/machv/cybairgaug.html

http://www.gadgetseller.com/gauges/modifiedproducts.htm

ion_four

I think they pretty much just add a capacitor in there to make the signal not jump around as much...atleast that's what I've read of some people doing...kinda lame. The limitation is not really the meter, but the o2 sensor itself. it's just not accurate away from 14.7:1 A/F, so it's not too handy for FI.
I have a voltage meter hooked up to mine. it works pretty well for what it is and costs next to nothing. I also have a DIY A/F bargraph display that I made from instructions similar to these.
http://www.scirocco.org/ (go to tech procedures, then misc. to find it) the only difference is that you don't actually need the 5v regulator. the chip can handle around 24v or something that it'll never see in a car.

filetofit

As i understand it, it's not so much that they aren't accurate, it's that they are nonlinear. THe rate of change of the output voltage of the sensor with respect to air fuel ratio is large right around 14.7. Away from this the value the voltage doesn't change much for large changes in air fuel ratio. So I suppose if you knew the non linear transfer function to go from voltage to air fuel ratio for the particular sensor, for the entire range of air fuel ratios, and had an accurate voltmeter you could do it. Interesting idea ....hmmmmm.

iranman

I think you guys are making this waaay more complicated than it needs to be. It has nothing to do with linearity. They've simply modified it so that the LED's light up at different voltages.

A regular A/F, say the Autometer version, has a row of LED's that correspond to O2 voltages between 0-1.0V. That's it. Now, somebody realized that >80% of the time, the output voltage is useless. So why monitor something that doesn't need monitoring?

Because desirable A/F ratios under WOT generally fall into the range of 0.75-1.0V, this person re-did the circuit so that the entire row of LED's fall within this range. It's not so much more accurate in terms of reading A/F mixtures, per se, but rather more accurate in reading O2 sensor voltages. Whereas before you could tell voltages somewhere between 0.8 and 0.9V, with this you can pinpoint it as 0.835V (for instance).

It's a decent upgrade. If I absolutely had to buy an A/F gauge, it'd be like one of these. Otherwise, save your money and have that **** tuned on a real wideband, and get it right the first time without the annoying lights.