shawnme

bros,
as far as i understand, O2 sensors should produce a voltage between 0-1V
so i went ahead with the diy project for the AF ratio ...and somehow..
when i tried to measure the voltage with the multimeter, regardless of the measurement point directly from the o2 sensor in the engine bay or the o2 sensor line from the ecu, it still gives me a reading of 2.8X volts and when i tried to rev a few times, it does show movement up to 3.1X volts.
so i thought maybe the sensor is not warmed up yet...so i waited for 20 minutes in idle mode...yet i still get the same reading..
so i'm wondering...what's the cause of this??...is this normal for my mivec gen 1 ???
i took measurements from 2 points just in case i got the wrong wire from ecu...and since i also measured directly from the o2 sensor itself, i dont think i got the wrong wire after all...
can someone enlighten....thanks ahead.
shawn

     

ecupro

I am not sure, but can give some knowledge.
You are right, normal o2 sensor will produce voltage from 0 to 1.0v or 1000mV.
This is narrow band sensor.
For A/F 14.4, voltage will be 680mV or 0.68V
On Rich Side, voltage will be from 780mv or 0.78v
Arrr....one thing, do not use analog meter, this will loading the sensor output.
So, please use digital meter.
In your case, i thing it is a wide band sensor.It will produce from 0 to 5.0V
For A/F 14.4, voltage will be 2.5V. It is ok.
On Rich Side, voltage will be from 2.2V to ZERO.
If the sensor only have one or two wire, this kind of sensor did not built in HEATER element, do it will take as least 3 minutes to head it up( Chemical reaction ).
If the sensor have 3 to 4 wire, Heater element is build in.So, only take less then a minute, you will get reading.
By the way, LED A/F meter or Digital meter you are making ?

     

shawnme

i used digital meter for my readings...and it's a wide band??!!!!...then how am i gonna get my AFr
coz i've never changed anything...it's still the same mivec halfcut i got...only that it's in my car now...

and indeed, it has only 2 wires....i measured each of them....one of them is ignition 12V+ and the other is the 2.8+ volts wire..

i'm making the LED AF meter thingy...just to know for kicks my AF ratio...haha...

shawn

     

ecupro

Hem.....
What i know is two wire sensor with one white and one blue.
I think the blue for ground and white for signal.
It is narrow band o2 sensor.
Long time, my engine come with one wire o2 sensor. Now, i change to Mitsubishi, two wires( blue and white, almost standard on all Mitsubishi, my engine is 4G61T )

     

sekut_kring

I got this from my collection....hope this will give your a little help.


In order to read the O2 sensor, most computers send out a certain voltage to the output terminal of the sensor. This is typically around 450 millivolts. Since we know that the sensor sends low voltage (under 300mv) when a lean condition is present and a high voltage (over 600mv) when a rich condition is present, the computer can count the number of times the sensor crosses the 450mv mark. Cross-counts are the number of times an O2 sensor crosses 450mv. A scanner can "look" at this for you.

Even though you can't see the number of cross-counts without a scanner, you can use a digital voltmeter to watch the open/closed loop system operate. Just connect your meter as attachment, while the O2 sensor is still connected, and start-up the car.

Caution: Do not ground the output wire of the sensor. This can damage the sensor and your readings will be erroneous.

When the car starts (cold), you should see approximately .450 Volt (450mv) on the O2 output wire. This reading often varies slightly. The system is now in open loop.

After a few minutes (less if the engine is warm or the O2 Sensor is heated), this reading should begin to fluctuate. You will see changing numbers ranging from near 0 volt to near 1 Volt. If these readings occur, everything is ok. The O2 sensor's output should vary relatively quickly. A lazy sensor, would show up here and the readings will vary slowly. If the readings don't start to vary (stay in open loop), you now are aware of it and can begin to look for the reason.

Attached Images

o2 sensor checking.jpg (3.5 KB, 174 views)

     

ecupro

By the way, why 12V on that wire?
Is it stock wire?

     

shawnme

bros,

i followed the advice of bro sekut_kring and finally i got it to work...

however, it's weird that my AF meter jumps up and down like disco lights...

is it due to the open/close loop of the ecu???

but i've seen my friend's car and it does not jump up and down like that...

at idle, he gets 1 led

during pick up..usually rich

and during cruising, 13.4-14.7 (around there - i forgot)

which i find it logical...

how come mine doesnt work this way??

shawn

     

ecupro

Bro, is it on the same car model ?
For Mitsubishi (my car when using stock ecu), during cruising for a while ( rpm around 2000 to 2500, town area ), the led will go from left to right, then, right to left. This is call close loop system. While crusing, the ecu will check on the o2 sensor. When on rich side, o2 will generate more votalge, in this case, you led display will go from left to right ( lean to rich ), the ecu will re-calculate the fuel( close loop system) and so the fuel will reduce, in this case, you led display will got from right to left ( rich to lean ), and the whole process will be repeat until you accelate your car.

     

shawnme

yes..i'm using stock ecu...everything is pretty much stock....

just that when i compare it to my friends 4G93 with evo ecu, it doesnt jump like that..it's pretty much stable and easy to read...

the difference in his car would be dyno with safc2 and a rechip done...

could it be the difference of the dyno?? coz it's pretth much jumping around most of the time...it's currently kind of pointless reaading anything out of the AF meter...as it makes no sense...hehe...

shawn

     

ecupro

Bro, try put one 0.1uf capacitor on the input circuit board. It may dumper a bit.
( one leg on input, one leg to the ground, parallel ok )
By the way, please goto the threads: Tunning with a EGT and have a look look.

     

Cheong Mou Kei 4G9XT

hmm...im using stock ECU but da reading oso stable wert

     

shawnme

i've read through the EGT topic...great info...however, i'll still leave the tuning to the dyno...coz i dont really trust my O2 sensor....

what i'm doing now is just for kicks...and a cheap way hoping that i could monitor my engine and fueling....not really hardcore into tuning and stuff...

its like some first point of reference for me if something is wrong with the engine...

i will try the 0.1 uf cap....

anyway, i'm still curious to how come everyone else's runs stable and mine still fluctuates in the waves...i wonder if it's because i skip one part of the project...i didnt use the 'voltage regulator' (LM340MP - 5.0) in the input ....

thanks ahead,
shawn..

     

shawnme

bro,

i somehow found a 0.33uf capacitor lying about so i plugged it in...somehow, i slowed down the motions a little...however, i still get fluctuating close loop signals...

i soldered the negative side to ground and the positive side to the O2 signal input...

does this mean that i have a get a 0.1uf capacitor to be exact to be able to stabilize the signal??

shawn

Attached Images

diagram.jpg (34.3 KB, 86 views)

     

ecupro

bro, Not 7805 ( 5 v regulator ), Its a 7812 ( 12 v regulator ).
From your circuit, it seem there is no capacitor for the in comming battery voltage, try to but 470 uf, 25v.( In order to filter noise and dumpper a voltage a bit.
By the way, the input wire from o2 sensor must be shield ( if you tap from the stock ecu socket, i think it is ok )

I thing, ground or earthing the wire is very important on automobile.
Those who add in hi-fi system will know what i mean.

bro, have to try...try...try