when im hitting wot, my o2 is reading around 950mV . is this very accurate at all? i know a wide band would prolly help alot, but is it safe to assume im running too rich?

 

Ive been looking for my post on this same question, but i cant find it.

Anyways ,I can see as high as 1200mv sometimes on my LB9. I thought that 800-900mv is somewhere near to stoich but thats a figure way off the top of my head. Ive also read that alot of sensors are different and dont read as close as others. Then ive also heard "Quit wondering and jsut get a WB02"

Im interested also though in what someone else says.

 

Sure it means something.

U might be rich, u might be lean.

It might be 9:1, it might be 15:1

U will never know unless u have a wideband hooked up.

If u generalize it, u can say yes its rich(not a guarantee by any menas however), so keep that in mind.

They also tend to fall off on WOT runs and the mv starts dropping further, even caught a couple on the log doing some 000mv at me :-)

later
Jeremy

 

It's never safe to assume anything!.

 

so basically without the wideband, im blind with the afr at wot?

 

Well, there's two problems: "are your rich or are you lean", but also "where are you rich or lean (in the powerband)"?

Yes, on my car 950 mV turned out I was VERY RICH. But it was not where I thought it was (in the power band) until I checked it with a WB.

 

mine jumps high and just stays there the whole time i am wot.

 

O2s op. range is 0V to 1 V

If your getting 950MV Id say your running rich.

200 Mv is lean, and so on.

But if its only running rich on WOT then thats what you want.

 

You are definitely rich. You are near or above the saturation point of the O2 sensor. While the sensor may be difficult to interpret at stoich due to its steep slope in that area of operation, it is actually better at WOT (approx 12.5:1). You probably want to see somewhere in the .850 mv range. This will vary dependent on the AFR requirements of your engine at WOT, the temperature of the O2 sensor, and the condition of the O2 sensor. But remember this sensor is the heart of the fuel close loop system so if it is bad other problems will show as well. Heated O2 sensors are somewhat better because they run at a more consistent temperature.
Anyway thats my 2cents worth, hope it helps.

Al

 

thanks, car runs fine in closed loop , it does its up down thing quite well. now i just need to learn a better to way to add fueling under only open loop wot

 

It's called PE fuel or Power Enrichment fuel. It's fuel added only at high throttle, and in open loop.

But, it seems that with 950 mV already, that it's looking plenty rich (of course I have to insert the disclaimer that a narrowband is like a weather vane, and only points in the direction of the wind).

 

Oh THANK YOU Great analogy! Now would you please tell them goofballs out there (Non-TGO) with the $24 Idiotzone AFR Meter that?
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I think them AFR meters are the root of alot of automobiles degradation. I have seen so many people trying get the green led to stay green.

 

thanks i checked it out, the PE vs rpm and under the 4200+ i dropped it about 4 points nad it seemed to help quite a bit already.

 

Remember to read the plugs, and replace them frequently, otherwise you might see your pistons starting to leave the motor.
Relying on just one sensor, to tune, is still assuming.

 

And if you have a big cam, you still might be 9:1 or 15:1 on the wideband. Any sort of big cam with lots of overlap will make the wideband read way off. And i'm not going to get into the argument about self-egring because, yes, if your headers are equal length and designed to promote scavaging it will happen, but yes you will also get some raw fuel down the exhaust.

What i've learned from tuning, right or wrong, is keep 02 in the back of your mind, but tune to max power and call it a day.

I sold my wideband on ebay within 3 months of owning it becuase it was not even close to being helpful. Infact, on a cam with a ton of duration and overlap it switched AFR's so quick it was useless as a tuning aid. The slowness and inaccuracy of the narrowband is actually easier to tune VE tables.

-- Joe

 

Well, I haven't posted on this topic in a while and probably a bunch of people new to the board haven't seen the chart I made which correlated WBO2 output (the original DIY WBO2) vs. a standard narrow band sensor...so here goes.

It's my opinion that ANY attempt in ANY way to assign ANY meaningful AFR to some narrow band O2 sensor voltage is completely a waste of time.

The attached chart has measured AFR (from a DIY WBO2) on the vertical axis, and NBO2 MV on the horizontal axis.

My particluar NBO2 doesn't get much above 900mV no matter what you do to it. Every NBO2 is different, and every application is different (depending on how far downstream the thing is mounted, how hot or not it is, etc.). The thing to get from this chart is that a NBO2 voltage is MEANINGLESS. Look at the narrow vertical red column I marked. This is the range of actual AFR values with the NBO2 reading 900mV +/-. Notice how the AFR is pretty randomly distributed between 14:1 and 10:1. That's how USELESS a NBO2 voltage reading is. It doesn't tell you a darn thing. It's really only useful as a switching sensor for closed loop feedback to tell the ECM when the AFR has gone to a leaner than stoich condition after being richer than stoich, or vice versa. Which it does well. Just don't try to assign an actual AFR value to some NBo2 voltage!

 

FYI, AT WOT my Narrow-band is over 1000 when my wideband is reading 12.4~-:1