Why using the factory O2 sensor is less than reliable when it comes to A/F

[Steve Wood]

Look at the first section on O2 sensors...The factory O2 was almost flat.  In fact it dropped about 15 mv over the boost part of the log, but, the wide band shows over a 2 A/F drop...and was actually getting richer as the factory was showing lean.

http://www.vortexbuicks-etc.com/tuning.htm

[Recklessrob]

If you look at the whole graph comparing the WB and th O2, the O2 seems to mimick the other sensors except the WB.

[Steve Wood]

Lost me on that one

[87natty]

That tuning page is something I'm going to have to print out and absorb while in my office. The bathroom, actually.

I'm amazed at how erratic the stock O2 is, even before the TPS even hits 2 volts. Damn.

[Steve Wood]

remember that the stock sensor is trying to maintain a 14.7-1 ratio until the ECM sees hard acceleration.  That means it has to rapidly oscillate back and forth .441 mv.  

Then look at the wb...it is hanging around in that a/f range....

If you look at the nb graph at the beginning, you can see it only means something right at that point.

[Recklessrob]

Lost me on that one

You see boost and fuel pressure stay fairly stable, and the stock
O2 sensor seems to mimick that while you see the WB gradually descend into the extremely rich zone.All just befor the throttle was released.

[Steve Wood]

Lost me on that one

You see boost and fuel pressure stay fairly stable, and the stock
O2 sensor seems to mimick that while you see the WB gradually descend into the extremely rich zone.All just befor the throttle was released.

Boost and fuel pressure should stay constant at wide open throttle.  Neither is related to either the narrow band sensor, or air/fuel ratio as measured by the wide band.  Boost is controlled by the user and fuel pressure is directly related to it.

If you looked at/read the section on the factory o2 that I linked, you would see that the narrow band is only meaningful, by design, at 14.7-1.  It is a switching sensor.

The wide band, on the other hand, should be accurate somewhere between 10-1 and 20-1 depending upon the brand one buys.

The narrow band's voltage output is also greatly affected by both heat and pressure whereas a properly installed wb is not.

The point of my post is that one cannot tune accurately across a band using the factory sensor because the A/F may not be what one desires.  All one can do is to try to lean the car down until one reaches the edge of detonation at the top of third gear...but, that may not be optimum at other points.

The comparison shows that the air fuel ratio actually varies from over 12-1 early in the run to less than 10-1 before he lifted.

In fact, the factory 02 dropped slightly with time signifying, in theory, that the mix was leaning, when in fact, it was going pig rich.

Without the wide band, one would have thought the car was nice and lean with the o2s in the 780 mv range whereas it was almost choking on excess gas.

[Top Speed]

I can't believe that people still use the stock sensor to tune with.

[Steve Wood]

Long as one stays out of detonation, it works...but, in today's generation of programmable chips, one can leave a lot on the table

[Steve Wood]

Bringing this back to life, I am chaning my mind.  WB's are nice when they work, but, they are not necessary, imo, when a car is in the high tens, or elevens....

And with a closed loop programmable chip, one can be in deep dodo if the wb fails and does not have a default value that can be used to save you from yourself.

the main thing that needs to be remembered is that the nb reads totally different at idle and cruise than when at wot under boost and high egt.  Having said that, I have found the nb to be pretty repeatable with regard to voltage output under a given condition.

rather than trying to figure out what it equates to a/f wise, just try to find the minimum voltage that you can run in the top of third gear without having any timing retard....

Lean is mean...if too mean, then you can pick up pieces and it does not matter what kind of o2 you had installed

[SuperSix]

For some reason, I always use Bosch sensors. I hear NGK is good too.

But my TR is  basically a stock, street car.

[Steve Wood]

I have always heard that Bosch were not as good as Delco, but, lately, I have heard from several that said the Delco had a tendency to freeze at times...

Altho I am running speed density chips from TT in both of my cars that use either nothing, or a wide band, I put the Denso sensors in for the factory unit just because I feel better seeing it and knowing it is working.  Maybe if I had something other than the Innovate wbs, I would be more confident

[2QUICK2B6]

Always ran Bosch here also any good bad news on Denso ?

[Steve Wood]

always heard bad about Bosch and good on Denso...I have only run Denso in recent years, but, being I am SD and either open or closed on the wb, it really has no function other than as a monitor.

Denso reportedly holds up under lead for a longer time before acting up

[Turbodave]

I run both.  Narrow band and wideband, and they both controle the car in their own specialized environement.

While at part throttle, that is to say, idle and cruise, the narrowband is in control, because in all the testing and data logging I've done over the past couple years, the narrowband just can't be beat for really really tight control at these condtitions.

However, it's out of the picture when at WOT, so I use a wideband to control things at WOT.

The best of both worlds!!!!!!