0.5 volt dc battery to fool O2 sensor? - Page 2 - Fuelly Forums

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Old 11-25-2007, 02:32 PM   #11
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I had a mid 80's K car that had a feedback carb that would run fine without ever being plugged in.

The 100K pot is a variable resistor.
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Old 11-25-2007, 02:44 PM   #12
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I wouldn't recomend doing it this way either, the o2 sensor is part of a looped system, it's a sensor that is performing an important job and bypassing it just seems like a bad idea.
if you want it to run leaner, people have wraped aluminum foil around the out side of the o2 sensor, as they work by reading the differnce between the o2 content of the exaust, and the o2 in the air on the outside of the sensor, so if you limit the amount of of air that comes in contact with the outside vents of the sensor, then it's going to lean out the mix in a controled manner.
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Old 11-25-2007, 03:52 PM   #13
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Pot is short for potentiometer which is a variable tapped resistor that can be used as a voltage divider.

You don't want to remove the O2 sensor from the system - what you want to do is add a bias to its output to make the ECU think you are running rich so it will lean out the mixture the amount that you bias it towards rich. That may require a little current from a 1 to 1.5 volt? source through a Pot which will allow you to vary how much rich bias you feed the O2 sensor. THis assumes that a rich sensor reads higher voltage and a lean sensor reads lower voltage. You should use about 50x the resistance of the O2 sensor for the pot or even higher so you only apply a 1/50th or less bias relative to the full output of the O2 sensor. You only want a small variation in the A/F mixture.
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Old 11-25-2007, 04:04 PM   #14
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I need to clarify my earlier post:

Quote:
I had a mid 80's K car that had a feedback carb that would run fine without ever being plugged in.
I said that in response to the earlier thread that mentioned the car going into limp-home mode. It will still run ok(won't leave you stranded) but it will, if I remember correctly, default to a rich setting which means removing the O2 sensor completely would be a bad thing.
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Old 11-25-2007, 04:22 PM   #15
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i did this mod with a 4 wire sensor, only i fed a few 10ths of a volt through the o2 ground to raise the voltage at the output.

everyone *****ed at me and no one bothered to actually try it. i wouldn't know how to raise the voltage of a single wire o2, but if you want to install a 4 wire, i can tell you how to do that. pm me.
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Old 11-25-2007, 04:30 PM   #16
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From what I have read - a 4 wire O2 sensor is a sensor with a heating element in it to warm it up electrically with 12 volts? so it starts working sooner. It can read A/F ratios as long as it is warm enough and by having an electric heating element in it - it doesn't have to wait for the Cat to warm it up to operating temperature.

Makes me wonder if leaving the ignition key on for a few minutes before starting the motor would preheat the O2 sensor more and get it working SOONER thus saving fuel!!!!
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Old 11-25-2007, 04:34 PM   #17
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Quote:
Originally Posted by csrmel View Post
i did this mod with a 4 wire sensor, only i fed a few 10ths of a volt through the o2 ground to raise the voltage at the output.

everyone *****ed at me and no one bothered to actually try it. i wouldn't know how to raise the voltage of a single wire o2, but if you want to install a 4 wire, i can tell you how to do that. pm me.
I think that you would only need .300V give or take to be effective. Too much would cause an open-loop like condition.
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Old 11-25-2007, 06:50 PM   #18
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Originally Posted by Ryland View Post
if you want it to run leaner, people have wraped aluminum foil around the out side of the o2 sensor, as they work by reading the differnce between the o2 content of the exaust, and the o2 in the air on the outside of the sensor, so if you limit the amount of of air that comes in contact with the outside vents of the sensor, then it's going to lean out the mix in a controled manner.
Theres a much more robust way of acomplishing the same thing without resorting to aluminum foil which might destroy an oxygen sensor.

Not sure if the threads are standard on all oxygen sensors (quite possibly are as every car I've changed O2 sensors used the same O2 socket I have...

Anyway, I hate to admit this but back in my racing days when we went to the track we would install track pipes. Basically they were short sections of exhaust pipe that replaced the catalitic converter with a straight pipe. The pipe had a bung in it for an O2 sensor.

Now some people wanted to run this track pipe all year round for the increased performance but running without any cats would set off the CEL.

What they would do is get whats called a spark plug anti-fouler from their local automotive shop (pep boys, advance auto, etc...) They come in two different lengths, long and short. It looks like an extension sort of.. anyway, there are thread on the outside and inside of the adapter. There is alot of excess metal on the inside of the adapter to make the hole small.. you can take a 1" drill bit and drill out the adapter on the long one (make sure not to drill the threads on the inside!!).

All you have to do then is screw the long one into the short one (leaving the short one undrilled) and then screw your O2 sensor into it. Then take the whole assembly and screw it into your exhaust. It will stick out about 2" more than normal so this is only really possible if your O2 sensor isn't sticking out towards the ground (don't want it to hit anything)

It pulls the O2 sensor out of the exhaust path far enough for it to not sense as much exhaust gas, thereby should fool your car into running a bit leaner.

The reason they did it was because running without cats not only made their cars unable to pass emissions but also run richer... this fixes it.
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Old 11-27-2007, 03:29 PM   #19
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Originally Posted by caryfd227 View Post


What they would do is get whats called a spark plug anti-fouler from their local automotive shop (pep boys, advance auto, etc...) They come in two different lengths, long and short. It looks like an extension sort of.. anyway, there are thread on the outside and inside of the adapter. There is alot of excess metal on the inside of the adapter to make the hole small.. you can take a 1" drill bit and drill out the adapter on the long one (make sure not to drill the threads on the inside!!).

All you have to do then is screw the long one into the short one (leaving the short one undrilled) and then screw your O2 sensor into it. Then take the whole assembly and screw it into your exhaust. It will stick out about 2" more than normal so this is only really possible if your O2 sensor isn't sticking out towards the ground (don't want it to hit anything)

It pulls the O2 sensor out of the exhaust path far enough for it to not sense as much exhaust gas, thereby should fool your car into running a bit leaner.
Thanks- I like this idea better than adding extra voltage and possibly frying the oxygen sensor, control box or both. This also seems to preserve some of the functionality of the sensor while leaning things out a little bit.

Maybe I'll get around to setting up this test during the weekend.

The aluminum foil method seems easier, but I don't want to damage the sensor. How/why do you feel this could damage the sensor? Maybe a reaction between the dissimilar metals?
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Old 11-27-2007, 04:16 PM   #20
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Thanks- I like this idea better than adding extra voltage and possibly frying the oxygen sensor, control box or both. This also seems to preserve some of the functionality of the sensor while leaning things out a little bit.

Maybe I'll get around to setting up this test during the weekend.

The aluminum foil method seems easier, but I don't want to damage the sensor. How/why do you feel this could damage the sensor? Maybe a reaction between the dissimilar metals?
Well with all mods of this type your taking some risk... but IMO aluminum foil is mighty thin and exhaust gas is hot. All it takes is a little corrosion and a bit of it breaking off and lodging in your cat or making its way into your O2 sensor damaging it.
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