This has been discussed in random places, but I thought I would start a new thread to get all the collective thoughts. Is a narrowband (stock) O2 sensor to an aftermarket A/F gauge worth looking at? Is it at all accurate?

 

I have a GReddy one that, while not used for tuning, can be very helpful. In the event my engine goes lean I will immediately notice it on my gauge and will then have the chance to let up. For the most part it just sits in the rich area when on boost and may twitch towards stoich so in my case, as a piece of equipment that can keep me informed of diaster, I like it. It is also great for tuning while crusing. I tuned it on a trip I took down the highway and ended up getting about 23mpg for the highway

 

He's talking straight up stock single wire o2 sensor. I believe the GReddy is a 4 wire o2 sensor that they use? which is more accurate but still not as accurate as running a wideband.

 

Oh, straight up single wire, yah, worthless. It is designed to do what it does, closed loop operation

And yes, the GReddy is 4 wire so it is heated, but most people will still say it is worthless But as I said, I use it as an emergency meter

 

Wrong.
Wrong.
In installed correctly, wrong.

Read Cosmo Donk's first post, so far he's the only one who knows what he's talking about. A/F gauges are a useful monitoring tool if you understand exactly what you're seeing and know how O2 sensors work. Most here don't seem to...

 

Ya know, I'm just going to delete all wrong/useless posts...

 

But then there wont be anything left to read! j/k

 

SO when does the stock O2 run then? I though it was on at certain situations so some times it will read differently.

I am trying to remember but something like at idle it will be wacky.

 

Woops I voted 100% useful by accident, I meant to vote can be used but not very accurate.

 

I agree, these gauges are nothing you should "tune" with. And for the cost of those Greddy gauges that is a lot of money for a warning light. I would rather use an EGT gauge at least I would feel the information would be more accurate for the cash I was spending.

- Dana "if it's from Japan triple the $$$"

 

The real problem is the range in which the stock sensor is accurate. They are really only good around 14.7:1 So using them for tuning isn't really going to get you very far. You could use it to tell you if you are going (dangerously) lean, but that's about it.
You really need a WB for tuning.
Good luck

 

The oxygen sensor "runs" all the time (i.e. you can read it's output voltage), but the ECU only uses it during light-load cruise. It's only truely accurate around stoichiometric mixtures.

 

is there a way to install it incorrectly? im just curious

 

Anything can be installed incorrectly...

 

"First, about the stock O2 sensor: As others have said, it is designed to zero in on the 14.7:1 A/F ratio the catalytics like to see. Second, it has a total range of 0-1 volts. What others have not said is that a huge percentage of that range is dedicated to A/F ratios near that 14.7:1 ideal.

To be specific, about the 70% of the O2 sensor's output range (about .14v to .8v) corresponds to an a/f ratio range of roughly 14.5:1 to 15:1. Thus, you have only about 30% of the O2 sensor's range remaining to describe anything richer or leaner than that. Looking only at the richer end of the spectrum, and limiting that to the A/F range of 10:1 to 13:1 (where all performance tuning takes place), you only have a paltry one tenth of one volt to work with.

Now, smart people can make gauges sensitive enough to accurately read within a tenth of a volt, but there is another problem. The central 70% of an O2 sensor's range is very stable over the normal range of exhaust temperatures. The outer 30% of the range (including the rich end) is not. This is especially bad news for owners of rotary cars. Taking a lead from the software of my Electromotive system, I would guess that A/F meters are made assuming exhaust temps in the 550-600C range. Rotaries routinely operate in the 800s under boost. Finally, it has been my experience that manufacturers of O2 sensors don't care much about accuracy in the "performance range." Cars are not referring to O2 sensor output when the pedal is to the metal anyway, so there is no reason for manufacturers to pay a lot of attention to it. Some O2 sensors simply give up producing voltages in the range where you need them. "

"These have been around for a long time. They typically divide the entire O2 sensor range into 1/10 volt increments. The 8th LED will come on at .8 volts. I have one unofficial chart claiming that this corresponds to an a/f ratio of 13.2:1. I have another graph (Electromotive again) that shows .8 volts corresponding to more like 13.8:1. Going to the 9th LED, the first source says it is 12.7:1, while the second source says it is more typically 13.1:1. It is rare that any actual A/F information is printed on these gauges. Most just tell you where 14.7 is, then give rough guidance of which direction is lean, and which is rich. My old K&S meter shows an arrow pointing toward 12.8, but seems to be placed in a purposefully vague position.

Is there any use at all for a 10-LED A/F meter? Sure. Lots of engines (even 3rd gen engines) have died because of a failure (clogged fuel filter, for instance) that put the engine in a lean condition. Also, these little gauges will cycle when the engine management system is in closed loop mode (using the O2 sensor to find 14.7:1). Even when tuning something as sensitive as an aftermarket engine management system, one of these little gizmos can be handy for seeing momentary problems such as a badly adjusted acceleration enrichment, or what is happening when you are trying to tune around optimal cruise conditions at 14.7:1. "

 

tid bit of info i pulled from scuderiaciriani

 

How would you install it incorrectly?

it has 3 wires. a red (12v+), black (ground), and purple (tie in with o2 sensor.

Most people will pull this from the large white wire coming out of the ECU. (can't think of the pin off hand since I pulled my autometer a/f gauge out over a year ago).

The wiring from the autometer gauge is a bit on the small size which could possibly get interference from any larger 12v wire. Hense why you don't run your RCA's for a stereo on the same side as you run your 12v power to the amp. So unless you clip the wire, run shielded to the the splice in with the o2 sensor it would be possible to get interference from surrounding wires. The only way I can think of improper installation is not using the correct lead for the o2 sensor or bad connections.

For a vague tuning sure.. but for anything above that I don't see how people would trust their motor to a single wire sensor that has variables that could seriously affect it's readings (temp, condition, carbon buildup).

 

By making the signal connection in the engine bay. If you make the connection at the ECU, no only do you eliminate the problems caused by damaging the factory shielded cable, you also avoid any interference issues.
Actually they don't. Many people have connected at the sensor, and then posted here about the problems this causes. Unfortunately I believe the AutoMeter instructions are directly responsible for this.
This is the bit I find frustrating. You're not supposed to use it for tuning in the first place! That's not what it should be used for. As I keep saying, it is a useful monitoring tool, not a tuning tool. If you know what to look for, it can immediately show if the engine's not running properly.

 

I know quite a few people who have used a narrowband O2 sensor to tune their NA engines, which tend to use AFR's closer to stoich than supercharged engines. The trick is that you have to know what you are doing. Therefore, you are probably right, most people should only use it as a monitor.

Yes, but only according to the people who are trying to sell you one. If you think about it, high-performance engines have been around long before the wideband O2 sensor was invented. It is simply a tool, not some magical device that automatically makes a newbie into a professional tuner.

 

I agree with what the scuderiaciriani site says about the autometer a/f gauge for being good for warning signs of something failing. Other than that I just have known it as an annoyance in my interior of lights going back and forth. on the scuderiaciriani site it was discussed about how it can be modified to make it more useable.

A wideband gives you an easier way of targeting a projected a/f ratio with more accuracy.