ok so dont laugh but amazingly it works....i also have a feeling ima be flamed for the first time...


step 1 buy cheap volt meter
step 2 connect volt meter to 02 wire and other to ground and wallllaaaaaaaaa
step 3 dont flame
step 4 .10 .15v is lean .4 .5v ish is good and .8v is pig rich
step 5 mount voltmeter inside car.......

oh and i did doo a comparison with an actual a/f meter

i am running lean to vacuum leak i think whaaaa

 

I like it and am deffinitly going to do that to my 87.

 

intresting, ill have to try it

 

definitely trying that tomarrow, never would have thought of trying that, someone needs to compare to a real guage

 

I thought narrow band only sees Rich or Lean, not inbetween?

 

this isnt a narrow band its using the factory o2 sensor so i guess you can say its all band... by the way my cheap multimeter has a back lit display!!!!

oh yeah i learned this trick at school...uti

 

stock O2 sensor IS a narrowband.

 

oh well i did not know that...but that peeks my curiosity....what does it measure then?? 12to1 too 16to1????

 

that, i do not know!
LOL

 

13b lover,


Yes you are correct, however thats just a narrowband o2 sensor.

Those are only accurate from 14.0:1 to 15.4:1 AFR, well outside anything but cruising conditions.

You need a wideband o2 sensor for every other conditon... 5 wire preferably...

 

I wonder if its anyway to get an acurate reading on a normal stock vehicle? Ive got a VW Jetta that im curious about.

 

sometimes you need to only use a DMM to read this signal, as the analog volt meter can use too much energy and keep the ECU from being able to read it.

 

Curious...I go to uti as well. Glendale Heights represent!

anyway yea some of the newer cares are coming with a wideband allready, so sure you couls tap into it, but theres not much you would really want to do to change it, as they are damn good at keeping the engine at 14.7.

Older cars???? Sure you could use it to get a rough estimate but thats about all its good for. Which if you think about it is good enough for us cheap bastards.

 

That's really all a Air/Fuel gauge is. Whether it's wideband or narrow. All it does is display whatever voltage the o2 sensor is creating.

 

That's really all a Air/Fuel gauge is. Whether it's wideband or narrow. All it does is display whatever voltage the o2 sensor is creating.

 

There's a myth about narrowbands that everyone seems to believe. This myth is that they "only read rich or lean" or are only accurate in a certain range. That's not necessarily true, depending on how you think about it.

Most of the narrowbands will read from mid 11s to mid 17s without an issue. HOWEVER the difference between 11.5 and 13 is only about 150mV, while the difference between 14.5 and 15 is about 400mV. So there is a LOT more resolution closer to 14.7 then at other values, but the sensor is still technically capable of reading those other ratios. Interestingly, the difference between 15 and 17 is only about 150mV as well. Which of course is why widebands are used for tuning and in most modern cars for closed loop fuel control.

But to say the stock sensor is incapable of reading other ratios besides 14.7:1 is not really true.

 

biggups to mah main mans A to the C he is correct....Raspect maun.....

 

so now they are teaching "tuning" at UTI?

rofl....

and this 'trick' is pretty worthless unless you know how to interpret the signal and/or even have a piggyback or way to trim out the fuel. most DMMs are slow reacting where narrowband O2 sensors are very fast reacting so you could be interpreting the signal wrong as well.

you are taking what you learned in school beyond what the teacher was trying to teach you.

 

how many UTI students does if take to change a spark plug?

 

I think its a cool poor-mans AF/meter, but without a reference point or REAL air-fuel meter to compare, it really only just changes with my ratio.... what it actually means is another thing.

I bet deep down in the FSM or elseware on the net there's an o2 sensor voltage reference that might be able to be used.

 

Like I Hate Ricers said, make sure it's a DMM. My understanding is that the voltage reading may be high (.45V stoich), but the current that the sensor sources (it's like a battery) is extremely low. Adding extra taps into the O2 sensor wire will reduce the voltage and the ECU may read the AFR incorrectly. You will see an AFR dependent voltage swinging around with that setup though!

FYI, my OctoLogger only takes a few femptoamps from its sensor inputs, so it's ok to use for most sensors.

 

a narrow band o2 sensor (like the stock one) is basically a switch. at 17-14.8 afr, it reads in the range of 0 to 150 mV. from 14.6 to 11, it reads between 850-1000mV. this works great for the stock computer, since all it is trying to do is maintain a stoichiometric mixture (14.7:1) so when it sees high voltage, it subtracts a little fuel, when it sees low voltage, it adds a little bit. thats why if you did this on a stock car with the o2 snsor hooked up and everything working properly, you would see the voltage constantly oscillate back and forth.

this output is pretty much useless for tuning because:
a. it isnt particularly accurate at telling any real lambda reading, other than stoich.
b. the signal is such low potential that even a tiny interference can skew the reading by a big margin.

a narrowband sensor is 99% accurate at telling the one thing it was designed to find: rich or lean. it is NOT accurate at all in telling any particular ratio, and hence cannot be used for tuning.

for anyone who is really interested, an o2 sensor is an encapsulated yttria stabilized zirconia cell which undergoes an electrochemical reaction based on the difference in oxygen partial pressure between the outside air and the exhast. the bigger the difference, the higher the voltage. when you run rich, you use all fo the oxygen in the air, so there isnt much left in the exhaust, hence a bigger partial pressure difference and a higher voltage. the opposite is of course true for a lean condition.

a wideband sensor works in the same way, but ti is designed to output a relatively linear voltage curve as opposed to the step-like output of the narrow band. this linear curve is not particualrly easy to produce, hence the need for a contoller for wideband sensor use.

pat