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Old 05-24-2009, 07:29 PM   #1
Blase
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Default AFR gauge impressions and question

Before I post my little story, I would like to address the fact that yes I have read the many threads regarding narrowband AFR guages and how they are basically useless. This is further proof that the popular negative opinion towards these light shows is true.

A while back, a friend of mine gave me an old narrowband guage that he didn't need anymore for free. After reading the threads on here about them, I never really had any inclination to install the thing. However, a few days ago, I decided to ghetto-rig it so that I could use it to test the differences in readings between my stock and catless exhaust, stock and reflashed ecu, and possibly to check if any sensors are going bad (by swapping sensors with friends and see if any changes occur in readings).

I wasn't expecting anything accurate, but from what I got I really think that these gauges are garbage. I used kastle's write up on scoobymods.com as a reference for the install, except that I didn't cut or splice any wires. I strictly did this to test if it would work. Instead of splicing the ecu harness, I was able to connect the guage's wire by sticking it near the connector.

AS soon as I started up the car, the guage starting reading the AFR and it slowly rose up all the way to rich. Now, this is where I was going to come back and ask you guys what you thought about it. I was going to ask if this was because the catless exhaust and the ecu reading too much emissions or if it was just a bad reading. However, I found something quite peculiar when I disconnected the guage completely, hooked it up to a battery only, and found that the guage was still reading AFR levels all the way rich. How could it be getting a reading if it wasn't hooked up to anything?

Anyway, I just wanted to post up and see what other people thought. I was going to ask if using this guage was a reasonable method to try to test differences between mods and possibly sensors on their way out, but I think I have my answer.
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Old 05-25-2009, 01:42 AM   #2
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All it reads is a voltage offset between two points. 0V will read as rich. You didn't have it wired in right.

But yes, it's totally useless anyway.
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Old 05-25-2009, 02:07 AM   #3
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I've heard that the front O2 sensor is actually not a narrowband, but not exactly a wideband either - sort of a ...middleband.
Can anyone confirm this?
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Old 05-25-2009, 02:09 AM   #4
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Well, I'm glad I didn't splice wires for no reason. I'm still puzzled as to why the gauge was getting any kinds of readings after it was diconnected from the ecu. I tested if it would even light up on a battery before I installed it and it didnt show any readings. After I uninstalled it, I tried the same, and it was still maxed out at rich like when it was hooked up to the car. Now, even a few days later, it is still getting readings when I hook it up to the battery even though it hasn't been hooked up to the ecu. It's just all a bit strange to me I guess. It's like ghost in the machine.
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Old 05-25-2009, 02:12 AM   #5
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Quote:
Originally Posted by XanRules View Post
I've heard that the front O2 sensor is actually not a narrowband, but not exactly a wideband either - sort of a ...middleband.
Can anyone confirm this?
That I don't know, but according to Kastle the wire I had hooked it up to was for the rear o2, so it was narrow to narrow. I figured this would be actually accurate because of the lack of cats in my car. But whole experiment was useless though.
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Old 05-25-2009, 02:21 AM   #6
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Quote:
Originally Posted by Blase View Post
That I don't know, but according to Kastle the wire I had hooked it up to was for the rear o2, so it was narrow to narrow. I figured this would be actually accurate because of the lack of cats in my car. But whole experiment was useless though.
I'd like to find this write-up, I can't find it
The primary difference, as I understand it, is that the front O2 sensor is 5v, the rear is 0-1v. If there were a way to get the gauge to run on 5v rather than 0-1v, theoretically the readings would be far more accurate.
Especially because of the fact that my rear O2 sensor is plugged anyway
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Old 05-25-2009, 02:29 AM   #7
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emailed my contact at Autometer. Let's see what he says.
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Old 05-25-2009, 11:02 AM   #8
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Keep in mind also, that these o2 sensor must be up to operating temperature before they work correctly. Your strange readings in open air could easily be due to that.
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Old 05-25-2009, 06:07 PM   #9
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Quote:
Originally Posted by Skidd View Post
Keep in mind also, that these o2 sensor must be up to operating temperature before they work correctly. Your strange readings in open air could easily be due to that.
The thing is, the sensor wire wasn't hooked up to anything. Only the negative and positive battery terminals were hooked up to the gauge. Yet it is still holding a reading..

http://www.scoobymods.com/forums/aut...uges-t153.html - link to Kastle's write up.

Edit: On 2nd thought, I never disconnected the battery. Would that even make a difference? The ecu reset anyways since I diconnected the harness.
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Old 05-26-2009, 12:29 AM   #10
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it might.
It looks like there's nothing preventing one from wiring it to the front O2 sensor...weird.
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Old 05-26-2009, 12:30 AM   #11
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The first line of post #2 contains the answer to the stuff you guys are still wondering about.
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Old 05-26-2009, 12:36 AM   #12
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Quote:
Originally Posted by williaty View Post
The first line of post #2 contains the answer to the stuff you guys are still wondering about.
All it reads is a voltage offset between two points.

I dunno how that answers my question
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Old 05-26-2009, 12:40 AM   #13
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The gauge reads the voltage offset between the sensor signal wire and ground. It turns that voltage offset into an AFR to display. The gauge controller doesn't know or care if the sensor signal wire is hooked up to an O2 sensor, a battery, a gerbil running in a wheel, or just dangling in the air. It'll take whatever the voltage offset is and convert it for display.

When the signal wire isn't connected to anything, it's said to be floating. A floating input can do a large number of things, but the important thing is that you can never really be sure what the result is going to be. So when you had your sensor wire not hooked up to anything, the gauge was still merrily displaying the result for you. The result just happened not to mean anything.
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Old 05-26-2009, 01:11 AM   #14
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Quote:
Originally Posted by williaty View Post
The gauge reads the voltage offset between the sensor signal wire and ground. It turns that voltage offset into an AFR to display. The gauge controller doesn't know or care if the sensor signal wire is hooked up to an O2 sensor, a battery, a gerbil running in a wheel, or just dangling in the air. It'll take whatever the voltage offset is and convert it for display.

When the signal wire isn't connected to anything, it's said to be floating. A floating input can do a large number of things, but the important thing is that you can never really be sure what the result is going to be. So when you had your sensor wire not hooked up to anything, the gauge was still merrily displaying the result for you. The result just happened not to mean anything.
Ah, but that wasn't my question.
My question is why hook it up to the rear O2 sensor when the front O2 sensor has a much wider band?
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Old 05-26-2009, 01:16 AM   #15
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Ah, I was only addressing the question you asked at the end of your second to last paragraph.

And the front and rear O2 sensors work on different principles. The cheapassed NBO2 gauges can only read the rear.
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Old 05-26-2009, 02:41 AM   #16
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Quote:
Originally Posted by williaty View Post
Ah, I was only addressing the question you asked at the end of your second to last paragraph.

And the front and rear O2 sensors work on different principles. The cheapassed NBO2 gauges can only read the rear.
Hrm. Well, time to see if I can change that.
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Old 05-26-2009, 07:38 AM   #17
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Quote:
Originally Posted by XanRules View Post
Hrm. Well, time to see if I can change that.
You really can't. The front/wideband O2 sensors read very differently than the simple rear/narrowband ones, and it's a lot more than 0-5v scale versus 0-1v scale.

You'd think that if it was as simple as hooking up a narrowband gauge on a voltage reduction, it would have been done by now, yes?
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Old 05-26-2009, 07:06 PM   #18
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Quote:
Originally Posted by LetItSnow View Post
You really can't. The front/wideband O2 sensors read very differently than the simple rear/narrowband ones, and it's a lot more than 0-5v scale versus 0-1v scale.

You'd think that if it was as simple as hooking up a narrowband gauge on a voltage reduction, it would have been done by now, yes?
You'd think so, but who knows?
The worst that happens is I need to splice another wire
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Old 05-26-2009, 07:10 PM   #19
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Alright, Einstein, what's your little gauge gong to do when it's expecting voltage to change and voltage doesn't change?
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Old 05-26-2009, 07:18 PM   #20
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Quote:
Originally Posted by williaty View Post
Alright, Einstein, what's your little gauge gong to do when it's expecting voltage to change and voltage doesn't change?
explode!
Honestly, I don't know.
I'm just hoping there's some way for these to NOT be completely useless
I'm going into this like I go into most of my projects - swinging blindly and hoping to hit something.
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Old 05-26-2009, 07:31 PM   #21
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The only way to make a NBO2 display like that worth a damn is to feed it with the output of an LC-1 WBO2. Then it's somewhat useful.
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Old 05-26-2009, 07:49 PM   #22
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Quote:
Originally Posted by williaty View Post
The only way to make a NBO2 display like that worth a damn is to feed it with the output of an LC-1 WBO2. Then it's somewhat useful.
and LC-1?
I don't know what that is. Time to google!
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