I have been reading a couple of threads recently that involved people making judegments on the car's AFR by using the factory single wire O2 sensor.

Something that people should note about these sensors is that the narrow band will only read .5 AFR difference. The range is typically 14.2:1 to 14.7:1......meaning if you have an AFR gauge hooked up to the single wire sensor, and your gauge is reading lean - you could be anywhere from 14.8 and up, if its reading rich you could be anywhere from 14.2 down.

Just something to keep in mind when using the limited factory sensor

 

most people that are using the narrow band are also using things like an egt gauge to tune with however most people now a days know that a wideband is really the only way to go.

 

True, MOST people.....but yet there has been about 6 threads in the last week about people "running rich" and they are getting the reading from their factory sensor.

 

I got this pretty nice wideband off ebay for $350.00 by plxdevices. Got the M-250 with the 52mm gauge. Good times.

 

Many people underestimate the usefulness of a narrow-band gauge. If you notice it reading richer than it normally would under the same circumstances, then you are running richer. Even more importantly, even though you can't measure ARF under load, if the gauge reads leaner than it normally would under load, then you are running leaner. Or would you ignore it just because it's only a narrow-band...

 

So, pretty much what your saying is your kind of going with previous scenarios to determine the actual performance of your car. Aka.. your guessing.

 

It's not guessing at all, it's remembering. It's no different to reading any other gauge. If you see a different reading, you have a different mixture. Very simple.

 

^ werd .... all one has to do is know how to read the gauge .. its not a matter of it being in acurate its a matter of one being able to understand what its saying .... the oem o2 sensor cant be that inefficent because it seems to work fine for the computer correction factor .. a narrow band is like mega squirt .. u just have to know your vehicle in order to use ir properly ...

 

Yes, Im not saying that they are inaccurate - there is no doubt that they have correct readings and if you get a richer or leaner reading in the same scenario then you are richer or leaner. The only question is how much.

The problem is that the gauge only reads that small variation, so even though your factory gauge is reading rich, you may actually have a perfect 12:1. But you will never know - it could be 9:1...........thats ll Im saying. Is outside of 14.2 - 14.7 you have no idea how rich or lean the car is, you might know it is - just NO IDEA how much or little.

 

the problem is that that is WRONG.

while a narrowband is reasonably accurate in the 14.3-14.8:1 range, it is far less accurate leander than that, and completely useless when you get into the rich range. Not just inaccurate, but totally useless.

Here's why:

at, say, 800F sensor temp (which you have no way to measure) and 12.0:1 AFR it puts out say, 600MV. (I'm just pulling numbers out of my head here, for comparison purposes only.)
And say, the 3rd green LED from the right on your narrowband gauge will be lit.

The problem comes in that narrowband sensors are very sensative to temperature.
so at 750F sensor temp and 12.0:1 AFR it puts out 550MV and the 2nd light lights, despite the same AFR.
And at 900F sensor temp and 13.0:1 AFR it might put out 600MV again! and you think you are far richer than you really are.

So sometimes you'll see a different reading - and have the same mixture.
And sometimes you'll see the same reading - and have a different mixture.


It's useful for tuning cruise maps - but you probably shouldn't have to do that anyways. And it's totally useless for tuning a turbocharged car, don't bother even trying unless you want to break your stuff.