Eliminating Stock O2 Sensor - Tuning Forum

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Eliminating Stock O2 Sensor
Friday, July 07, 2006 10:15 AM
Is it possible to run whatever voltage the stock o2 sensor needs to think it is at stoich and then tune using only the wideband? Or to replace the stock o2 sensor with the wideband? The stock one is just so sperattic that it seems to me that it would cause more harm then good...... or maybe there is a way to convert the wideband signal to be on the same scale as the stock o2 sensor and run a wire to it... i dont know what would be good, im just brain storming... let me kno what you guys think



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Re: Eliminating Stock O2 Sensor
Friday, July 07, 2006 12:13 PM
If you just give it a constant voltage it will throw a code saying not enough switches, meaning the voltage hasn't changed enough times.

I used my secondary channel on my WB to replace the stock O2. The only probelm is it is not throwing a code for the missing heater circuit, I think a resister may take care of this though. I also remapped the output on the wideband to be a little more forgiving hopefully keeping the ecu happy.
Re: Eliminating Stock O2 Sensor
Friday, July 07, 2006 12:46 PM
i can turn off codes with hptuners... so running a constant would not matter.... but i would rather do what you mentioned... i was hoping that something like that would be possible...

so i can cut the wire going to the ecu and splice in the wideband wire after i change the output range to 1V instead of 5V ???

the problem is its not throwing a code? wouldnt that be good? or did you mean it is throwing a code? if you have hpt (im not sure if you do) you can just turn off codes that you know are comming up for no reason, or a explainable reason... like the second o2 sensor missing or cat missing...





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Re: Eliminating Stock O2 Sensor
Friday, July 07, 2006 12:50 PM
Opps meant that it is throwing a code. I just took the whole sensor out becasue I wanted to use the bung for my WB sensor. So now when the car tried to heat up the sensor it casues and error, but as I said I think a resistor will solve my problems. I don't have hpt so thats not an option for me.

Yes just cut the signal wire and connect the WB wire with a 0-1v signal. If you leave the stock sensor inplace you should be good to go.
Re: Eliminating Stock O2 Sensor
Friday, July 07, 2006 10:38 PM
J-Body's do not have a heated O2 sensor on the manifold, so are you referring to the after cat one?
I do know people have used a WB sensor in the stock location, they usually have a extra wire to give the proper signal to the ECU so it can function as normal, and still get your WB reading.



FU Tuning



Re: Eliminating Stock O2 Sensor
Saturday, July 08, 2006 1:58 PM
actually the eco 02 sensor is heated



1989 Turbo Trans Am #82, 2007 Cobalt SS G85





Re: Eliminating Stock O2 Sensor
Saturday, July 08, 2006 2:42 PM
Way bad idea.

You don't want to be in stoich all the time, specifically in power enrich and during deceleration.

Also, most Nerst cell narrowband simulators on widebands are 0-1v, our cars have a slightly offset Nerst cell system that goes from 0-1.250v. That is why the narrowband simulators don't work on our cars.

Eliminating the stock O2 is a bad idea, don't turn it off, don't run with the codes disabled, your car needs it to run correctly, stoich isn't what the ECU is always aiming for, so don't make it think thats what its running.





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Re: Eliminating Stock O2 Sensor
Saturday, July 08, 2006 3:59 PM
you could get a wideband controller that has programable outputs and make one a wideband and one to match the narrow band.
i did that with my lc-1.




Re: Eliminating Stock O2 Sensor
Saturday, July 08, 2006 5:22 PM
the wideband i got is referred to as a AEM UEGO Wideband Controller.... shouldnt I already have a "wideband controller" built in?? I think there is a knob on the back of it or something i heard that lets you change it...

so if i change it to 0-1.250 instead of 0-1v (the range i thought our stock o2 sensor was) or 0-5v (stock from aem i think) and run that info to the ECU then i should be ok right? you were saying that running the stoich voltage was a bad idea... but using the wideband instead is a good/not bad idea right?

... the only code i was going to turn off was the one that shows up for the heater not working...



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Re: Eliminating Stock O2 Sensor
Saturday, July 08, 2006 5:47 PM
0-5v would be the wrong range, and potentially burn out the circuit inside the ECU (sending it 5 times the voltage) not to mention the 0-5v on the AEM is linear, not nerst, and AEM does not have a 0-1.250v range. I have the AEM, I tried running it as a narrow band and it just didn't work.






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Re: Eliminating Stock O2 Sensor
Saturday, July 08, 2006 6:21 PM
that would suck to burn a circuit in the ecu!! wow, i would cry!! lol... but.. i knew that was wrong...

what is nerst?

because its not nerst then even if i get it to a scale of 0-1.250V's then it still wouldnt work?

is there anything i could buy to make this work?

im glad you chimed in before i went chopping wires and stuff



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Re: Eliminating Stock O2 Sensor
Saturday, July 08, 2006 8:03 PM
Sorry, I spelled it wrong, its Nernst Cell, if you type it into google, you can see what it is, in a nutshell:



That is the voltage output of a 0-1v Nernst Cell. Now, I've never seen my narrow band sensor go above 1000mv, but if you look up the specifications of the stock sensor it is a 0 to 1250mv sensor. You can see the very small mv range where the the sensor is outputting in the one lambda range, then the voltage climbs very fast to rich, or very quickly falls to lean. This is why such small swings in A/F produce wildly different mV readings from a Nernst cell sensor (and why the narrow band A/F gauges swing from rich to lean so quickly).

Personally I don't see a way to make it work, especially with the AEM UEGO. It just doesn't switch fast enough to pass the O2 sensor tests, and the ECU marks the sensor as bad and runs in limp mode.





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Re: Eliminating Stock O2 Sensor
Saturday, July 08, 2006 10:09 PM
My plan for this... (or until i get my welder, yes i know how to weld), when i install the turbo im going to hollow out the volvo cat thats on there (i go for emissions soon so i wont be needed another for 2 years... by then ill have a whole new exhaust anyway)

Im going to relocate the first 02 sensor to the second 02 sensors position (hollow cat so it shouldnt matter), then install my wideband 02 in the first position. I will just live with the code (leave the second 02 sensor plugged it, but out of the exhaust and somewhere safe) I will be redoing it with a 3rd bung for the WB when i make my new exhaust... But for now i thinkg it should be fine. I just dont want to put the turbo on without Wideband


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Re: Eliminating Stock O2 Sensor
Saturday, July 08, 2006 10:34 PM
Also not the best idea.

1. Lengthening the wire changes the resistance and the feedback of the sensor, this is why so many 2200's have problems with aftermarket headers.

2. The sensor will never get hot enough to switch back and forth fast enough, car will enter limp mode when it throws the switching code.






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Re: Eliminating Stock O2 Sensor
Saturday, July 08, 2006 11:16 PM
Good thing i posted it then lol. Anywho i made a deal with my brother, if he buys me the welder, ill install is high flow cat, teach him how to weld, and weld up any exhaust he wants in the future free of charge. I cant wait.


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Re: Eliminating Stock O2 Sensor
Monday, July 10, 2006 10:24 PM
stand alones are your freinds man.


"boobs now with Riboflabin"
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Re: Eliminating Stock O2 Sensor
Tuesday, July 11, 2006 11:34 AM
Jcavi wrote:

stand alones are your freinds man.


No, money and ease of use are my friends. Standalone is a headache I don't really want or need.

-Chris-



-Sweetness-
-Turbocharged-
Slowly but surely may some day win this race...
Re: Eliminating Stock O2 Sensor
Tuesday, July 11, 2006 12:03 PM
yea, the main reason i went with hpt was because it was easy to use, and no install required.... as time goes on, capabilities increase, plus whats there already is more then enough for most.... price is nice too even though megasquirt (which is what jcavi was referring to i think) is a good price as well





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Re: Eliminating Stock O2 Sensor
Tuesday, July 11, 2006 1:17 PM
Quote:

Acer Online
Friday, July 07, 2006 1:15 PM



Is it possible to run whatever voltage the stock o2 sensor needs to think it is at stoich and then tune using only the wideband?


why? you should always tune using only the wideband...

answer the question 'why would you ever need to do that?"

i'm curious to see the reasoning.

Quote:

The stock one is just so sperattic that it seems to me that it would cause more harm then good


...and what does this mean? I don't know where you're getting at with this post/ question

I think you need a lesson in the basics of tuning.

When you are in a partial throttle situation (read: non WOT / Power Enrichment, or PE), the computer constnatly adapts injector pulsewidth for stoichiometric air/ fuel ratio. because if you're in a non PE situation, ideally you want the best gas mileage you can get right? right.

Now when you mash the throttle, most ecus go into whats called 'open loop' (aka PE), which ignores the stock O2 sensor, and goes to a preprogrammed air/ fuel ratio table and spark advance table for maximum power.

Stock ecotecs however, don't go into this programming until 6200 RPM, but with HPT you can set that to 0rpm, so that whenever you mash the gas pedal, you go into PE which is what you want.

When you're in PE, your air fuel ration is more constant which will be reflected on your narrow band O2 gauge (although they are VERY inaccurate due to the 0-1.250V range or whatever it is). A wideband O2 sensor/ and gauge is the only way to properly tune fuel whether it be in PE or normal mode.

As was said, you can make ur wideband talk to the factory ecu, but in all honesty running two sensors is easiest even tho you're probably trying to avoid welding on an o2 sensor bung, aren't you?


if ur getting problems with fuel, consult this thread, it shows you how to turn PE on for the ecotec ecu (this is what you want)






Re: Eliminating Stock O2 Sensor
Tuesday, July 11, 2006 6:15 PM
hey!! Thanks for that info... although i knew most of it, im glad you chimed in give me a reason to bring this one back, because resetting my computer fixed the problem for about 10 minutes and i came upstairs to post it worked, and then after driving it for a day, things are back to normal

I know that then i am in closed loop the pcm uses fuel trims to add or take away fuel as needed to attain the magical 14.7 afr.... my problem is that my wideband reads 13.0 at idle and my fuel trims are are low as hell.... which tells me that my pcm THINKS it is at 14.7 because its not trying to do anything to change it...

I wanted to run the signal from the wideband to the pcm instead of the stock o2 sensor because it is more accurate and more consistant.... AEM recommends getting rid of the stock o2 sensor and tuning with the wideband with their standalone... i want my pcm to see the 13 that my wideband see's and not whatever the stock o2 sensor is seeing....

from the research i have done and brainstorming i have done with my friend i have deducted that it could be an exhaust leak that is making the stock o2 sensor think that there is not enough fuel and adding more fuel to compensate for what is not reaching the stock sensor and the wide band picks up the "actual" a/f ratio which is around 13.0 usually. I am not sure if this is possible however since the wideband is located after the stock o2 sensor and technically should see the same or less then the stock o2 sensor... maybe the only way my theory could be correct is if the wideband came first and then the stock o2 sensor and there was a leak in between... i dont know... but my stock o2 sensor is within 3 inches from the flange on the turbo and the wideband is at the end of the exhaust (2.5" open dump)

if there was a way to get the stock pcm to see a wideband i would love it!! or maybe a way to tell hptuners to tune af;s based on the input signal from the wideband :-o that woudl be awesome!! lol... i dont think its possible though

ANY INPUT at all is appreciated greatly!!

P.S. Damn GM and there 1.25 range instead of 0-1V that would have made my life easier... i need a device that takes the 0-XV signal and translates it to 1.250V's giving me the input the stock pcm is looking for....

Another P.S. I am getting a new exhaust soon, i will have more info then (i.e. whether or not it is a possible exhaust leak problem for sure)... thanks



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Re: Eliminating Stock O2 Sensor
Tuesday, July 11, 2006 6:50 PM
Quote:


I know that then i am in closed loop the pcm uses fuel trims to add or take away fuel as needed to attain the magical 14.7 afr.... my problem is that my wideband reads 13.0 at idle and my fuel trims are are low as hell.... which tells me that my pcm THINKS it is at 14.7 because its not trying to do anything to change it...


What do you mean by "low fuel trims"?

Do you know how the fuel trims work? I think that is confusing you, because what you said is incorrect.





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Re: Eliminating Stock O2 Sensor
Tuesday, July 11, 2006 6:56 PM
well i was just logging and the fuel trims are between 2 and -2 all the time, long term and short term...

from what i understand the pcm determines how much it needs to add or take away to get to 14.7 and over time it builds a long term fuel trim in an attempt to keep the short term one as close to zero as possible.... i might be wrong, that deduction is based completely off my friends input and other peoples posts, lol...




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Re: Eliminating Stock O2 Sensor
Tuesday, July 11, 2006 7:03 PM
Basically fuel trims are this..

The short term fuel trim adjust fuel based on what is going on right now. If the trim is one way or the other (positive or negative), then the ecu changes the long term trim in that direction and starts the process over again.

Positive trims mean that the ECU is adding fuel, thinking the system is too lean.
Negative trims mean that the ECU is removing fuel, thinking the system is too rich.

So, based on what you said, the ECU is doing the correct thing. Your system is showing 13:1, it wants 14.7:1, so its removing fuel (trims being low I'm assuming they are negative). So they ECU KNOWS its not at 14.7 and its adjusting correctly.

And you need to get it out of your head that the O2 feedback of a constant AFR means a better running car. The sensor bouncing back and forth is the ECU adjusting the fuel as the trims go, and its making the sensor switch so it can tell if the sensor is working correctly or not. If you watch your short term fuel trims, they go up and down very fast, almost in sync with the O2 sensor. Well its making the sensor switch.

It also allows the system to run a little lean over time on the highway for fuel economy.





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Re: Eliminating Stock O2 Sensor
Tuesday, July 11, 2006 10:22 PM
fuel trims are always below 2 and above -2 and USUALLY close to 0.XX.

there is not much adjusting going on....

i understand running a constant to the ecu doesnt mean the car is running fine, i just thought that if the pcm could see what my wideband sees it would know that fuel trims need to be at a really negative number to take enough fuel away for my car to idle at 14.7 and cruise at 14.7-15.1... i think if the pcm knew the afr was 13.0 my fuel trims would be very very negative numbers to take away fuel, and it would not hover so closely to 0 as if it is done adjusting

im going to log tomorrow and post the log for you to see what i mean exactly, ima figure out how to get my wideband hooked up so i can log it at the same time to show what i mean exactly...

thanks for your presistence in my seemingly ignorant posts... i am tryin to be clear



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Re: Eliminating Stock O2 Sensor
Wednesday, July 12, 2006 12:06 AM
I do get what your saying, but you seem to think that the stock O2 sensor is not accurate at reading stoich, when in fact it is EXTREMELY accurate in reading stoich, it is not accurate in reading anything else. You also have to remember that when you are idling cold, the system will be running rich. Mine idles when I start it up at 12:1.

Also, a 1.7:1 error in the AFR does not mean your fuel trims will go off the map to get the AFR back in line. Even short term fuel trims are trims over time, they are not instant.

If you think you are idling too rich, you need to adjust your idle VE table to bring your AFR back to where you want it. This is especially evident when you first start up the vehicle and before the system enters closed loop.





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