Air/ Fuel ratio gauge

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Postby Gary » Thu Nov 09, 2006 1:58 pm

FACT about A/F gauge:

- An A/F gauge is basically a voltmeter.
- It reads value between 0-1 volt.
Lean = .050 to .249 volt
Rich = .750 to 1 volt
Between these range the mixture is neither lean nor rich.
- A narrowband gauge/sensor can't tell you a specific value.
- In closed loop, it will keep bouncing back and forth between lean and rich because the ECU adjusts the fuel continuously and the output of O2 sensor is non-linear and very sensitive at stoichiometric A/F ratio
- When the ECU goes into open loop, it will dump the fuel. That's why it will read rich when you go WOT.
- An O2 sensor will not give a correct reading when it's cold.
- A narrow band gauge is USELESS in tuning.
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Postby gt4tified » Thu Nov 09, 2006 2:13 pm

Completely for aesthetics then huh Gary?
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Postby theUNYTEDone » Fri Nov 10, 2006 6:14 am

i know its useless, but even when my car is warmed up, the AFR gauge is seemingly nonfunctional... :shrug:
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Postby gt4tified » Fri Nov 10, 2006 11:58 am

theUNYTEDone wrote:i know its useless, but even when my car is warmed up, the AFR gauge is seemingly nonfunctional... :shrug:


and by nonfunctional you mean...?
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Postby syko says » Fri Nov 10, 2006 10:02 pm

i think nigel meant that the two red lines disappear. like it doesnt even light up after it is warm.
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Postby ___Scott___ » Fri Nov 10, 2006 10:11 pm

syko says wrote:i think nigel meant that the two red lines disappear. like it doesnt even light up after it is warm.

The O2 sensor could be wired backwards. The output voltage would appear to go negative as it warmed up.
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Postby ___Scott___ » Fri Nov 10, 2006 10:37 pm

There are write-ups all over the net on how to build your own cheapo DIY O2 meter/display, but here is one with lots of pretty pictures:
http://autospeed.drive.com.au/cms/A_021 ... larArticle

It will only tell you what the narrowband O2 sensor is putting out, which is of minimal value.
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Postby theUNYTEDone » Sun Nov 12, 2006 3:45 am

thanks, guys...maybe it IS wired backwards.
but yeah, i guess there's not much that i can do at the moment...
at least i get two little red dots during startup. =]
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