WTF did I do wrong???

[Dirty Howie]

Ok, Look at that same area (8300-8400) and notice the AFR that is indicated (average) is around 15.5 AFR. The Narrowband sensors will keep the AFR at 14.7 +/- .2 AFR roughly.
Here's what your wideband is reporting on average at cruise.
The yellow cursor is where you are in those frames on average. Looks "lean" according to the wideband but I doubt you were running that lean in closed loop with fuel trims near zero like they are.

Attachment 5689

That's why I think PLX has a calibration issue. The narrowbands will drag the AFR back to 14.7 because that's what they do...

Here's your LTFT's at the same point (PERFECT!)

Attachment 5690

Here is a log to work today...mostly cruizing. WB looks same but I have positive fuel trims now!!!!


DH

[2000C-5]

If the fuel trims are in line (DH's tune) but the wideband is reading 15.5 at cruise, then the wideband is off not the tune or the narrowband o2's.

It's all about understanding, so bear with me.

How did the fuel trims get in line to begin with if the wideband is off that bad? If you are using a wideband that is reading 15.5 when it is actually 14.7, which is the same as the wideband reading 14.7 and the actual being ~13.9. When tuning OL VE, you would be tuning the AFR to 13.9 (even thought the wideband is reading 14.7). Everything would look perfect until going to CL. Then the narrowbands would let you know that the tune was off. They would reflect this by showing you a bunch of -10s to -14s, because they are trying to bring the AFR back to 14.7 from, what is now, 13.9.

If the wideband was off while tuning in OPEN loop, then you checked it in CLOSED loop and the fuel trims were off substantially, then the fuel trims are correcting the wideband's error. Fuel trims are +/- 2-3% and can be considered accurate at highway cruise.

So, are you saying that +/- 2-3% fuel trims are good or bad? If you are saying that it's good, then this sounds like what I am saying: fuel trims are good, wideband is good.

[2000C-5]

Here is a log to work today...mostly cruizing. WB looks same but I have positive fuel trims now!!!!


DH

This seems to be showing correct wideband readings. You are lean everywhere and it shows in your trims and also in your AFR % Error chart having positive readings.

[Dirty Howie]

This seems to be showing correct wideband readings. You are lean everywhere and it shows in your trims and also in your AFR % Error chart having positive readings.

Well I hope you guys are interested in this as much as I am. So I went back to OL with MAF enabled. I am showing trims reading -.8 to +1.6 on bank 2 only and no short trims. Please check that I am properly in OL. Could be that I just need to reset trims which I forgot to do, but will do in the morning.

Anyways my AFR dropped way down to where it should be in non PE by just putting it in OL..... Why is that ???? And my cold start (which was at 97* ambient) showed AFR in the 19's...why is that???

Anyways I am going to tune the MAF below 7500 till it is spot on and then go back to CL and see what the AFR looks like then.

Here is my tune putting it in OL and the log.


DH

[Dirty Howie]

Anybody home???????

Doug: Here is a log from today after some Maf tuning 7500 and below. See histogram should look better in cruise areas. This is still in OL.


DH

[2000C-5]

Well I hope you guys are interested in this as much as I am. So I went back to OL with MAF enabled. I am showing trims reading -.8 to +1.6 on bank 2 only and no short trims. Please check that I am properly in OL. Could be that I just need to reset trims which I forgot to do, but will do in the morning.

You can remove the trims from your Table Display because you don't have any trims in OL. That way you can log something else if you need to. You don't need to reset until you go back to CL, cuz they ain't workin' anywayz.

Anyways my AFR dropped way down to where it should be in non PE by just putting it in OL..... Why is that ???? And my cold start (which was at 97* ambient) showed AFR in the 19's...why is that???

Anyways I am going to tune the MAF below 7500 till it is spot on and then go back to CL and see what the AFR looks like then.

Here is my tune putting it in OL and the log.

Since you've gone that far, why not go ahead and disable the MAF and check the VE. Then you will have eliminated all variables.

[Russ K]

You can tune all day long, nothing is going to change the fact that the WB is reading too lean. The fuel trims can move +- 25%. In closed loop the WB should read very close to 14.7 at steady rpm & load. The closed loop AFR will surge slightly rich or lean when the throttle is tipped, but will quickly recover.

You need to find out why your WB is reading lean.

Russ Kemp

[Dirty Howie]

You can tune all day long, nothing is going to change the fact that the WB is reading too lean. The fuel trims can move +- 25%. In closed loop the WB should read very close to 14.7 at steady rpm & load. The closed loop AFR will surge slightly rich or lean when the throttle is tipped, but will quickly recover.

You need to find out why your WB is reading lean.

Russ Kemp

Russ

Since I do have HPT and have the time (drive my car every day to work) I thought it would be a good exercise in helping me learn to retune the MAF so it was reading 14.7 which I basically have done...I think. So I will renable CL and see what it looks like.

I will be very surprized if my WB is reading correctly since both you and Doug seem to be convinced it is not


DH

[Dirty Howie]

I put it in CL and forgot to hit the record button on the way home. I will post a CL log tomarrow.

Russ

I guess you are saying (I'm trying to make sense of this ) that the WB readings that look good above in OL are not accurate.

And this is only evident when going to CL..........

...........something just doesn't click in my mind about the logic of this

I know I'm slow but I'm not a complete idiot ...............


DH

[EC_Tune]

Here it is in a nutshell:

In closed loop the PCM is correcting the fueling to keep the AFR at 14.7. And it's especially good at cruise speed where airflow is greater and throttle transitions are generally less abrupt.

Ignore what the fuel trims are indicating as they are keeping the fueling at 14.7 AFR (because that's what they are supposed to do).

The wideband is reading 15.3-15.8 AFR when the narrowbands are keeping the ACTUAL AFR at ~14.7.

So the wideband is incorrect by almost a ratio at cruise.

Now to throw a complete monkey wrench into this: If you were "simulating" the narrowband and the wideband was wrong then your fuel trims would be wrong as well by the ratio of the error.

[Dirty Howie]

Here it is in a nutshell:

In closed loop the PCM is correcting the fueling to keep the AFR at 14.7. And it's especially good at cruise speed where airflow is greater and throttle transitions are generally less abrupt.

Ignore what the fuel trims are indicating as they are keeping the fueling at 14.7 AFR (because that's what they are supposed to do).

The wideband is reading 15.3-15.8 AFR when the narrowbands are keeping the ACTUAL AFR at ~14.7.

So the wideband is incorrect by almost a ratio at cruise.

Now to throw a complete monkey wrench into this: If you were "simulating" the narrowband and the wideband was wrong then your fuel trims would be wrong as well by the ratio of the error.

Doug.....why did you throw a monkey wrench into your nutshell ??

I really am trying to grasp what you an Russ are saying. And I do understand the concept of the 02's and closed loop functioning to keep fueling at stoich.

......I guess what is confusing me is WHY am I seeing stoich AFR in the cruise cells NOW that I am in OPEN LOOP ????? Seems to me that they must be reading correctly???????????????????????????


DH

[Dirty Howie]

Ok, Look at that same area (8300-8400) and notice the AFR that is indicated (average) is around 15.5 AFR. The Narrowband sensors will keep the AFR at 14.7 +/- .2 AFR roughly.
Here's what your wideband is reporting on average at cruise.
The yellow cursor is where you are in those frames on average. Looks "lean" according to the wideband but I doubt you were running that lean in closed loop with fuel trims near zero like they are.

Attachment 5689

That's why I think PLX has a calibration issue. The narrowbands will drag the AFR back to 14.7 because that's what they do...

Here's your LTFT's at the same point (PERFECT!)

Attachment 5690

Well here is a log today in closed loop. I included an image to show how much increase in the Maf Freq after tuning. Seems like my AFR is closer to 14.7(compared to the log we were comparing to) but my fuel trims are much more negative than they used to be.

So why does the WB read one way in OL and another in CL

Plus my WOT goes richer than commanded now also.


DH

[EC_Tune]

In CL the "feedback system" (o2's) are keeping things at a REAL 14.7 AFR.
In Open Loop they only put out the "calculated fueling" based on your adjustments with no corrections by the o2's.

I like to tune the "normal driving" area with the narrowbands. Idle I cross reference to the WB. And WOT is wideband only.

[Dirty Howie]

In CL the "feedback system" (o2's) are keeping things at a REAL 14.7 AFR.
In Open Loop they only put out the "calculated fueling" based on your adjustments with no corrections by the o2's.

I like to tune the "normal driving" area with the narrowbands. Idle I cross reference to the WB. And WOT is wideband only.

I am still struggling with this in my mind.

My WB certainly is capable of reading 14.7 as it does in open loop and closed loop. It also is capable of reading richer and leaner as it does in both modes.

I understand what you are saying about how the O2's don't affect fueling in OL.....thus I thought my accurate WB readings in open loop!!!!!!.....and in my mind the 02's being off. But I'm sure I am probably looking at this backwards.

So we seem to only be concerned with the discrepency between WB and NB in the non PE cruise areas.......why would this be??




DH

[Dirty Howie]

Well if my WB is inaccurate how do I rectify this. Is it the sensor or the PLX box???

What would I tell PLX ........


DH

[2000C-5]

Well if my WB is inaccurate how do I rectify this. Is it the sensor or the PLX box???

What would I tell PLX ........


DH

Just out of curiosity, does your formula look like this?

(volts/.5)+10

[Dirty Howie]

Just out of curiosity, does your formula look like this?

(volts/.5)+10

uhmm....what formula??

I used the PLX pid and just inserted it in my table.

PS: do you understand how the PLX can read stoich in OL but 15.5 in CL ??? I really want to get it thru my head but it makes me when I try..........


DH

[2000C-5]

uhmm....what formula??

I used the PLX pid and just inserted it in my table.

PS: do you understand how the PLX can read stoich in OL but 15.5 in CL ??? I really want to get it thru my head but it makes me when I try..........


DH

I never did understand that. With good fuel trims, it had to have been reading correctly at some point anyway, or else the trims would have been off when you went back to CL and the PCM began pulling the 15.5s back to 14.7.

I was really hoping that you would find an air leak somewhere and that would have explained lean AFRs. What about the exhaust, check header bolts, check where pipes/cats connect unless it's welded, check gaskets.