TMO

I removed the cat and installed a "test" pipe with a heated NB O2 and a ZT-2 WB. I performed NB VE learns in the EBL and then performed a WB learn. (I now understand what you folks say about the WB telling you what is really going on.)

Now the WB questions:

1) The VE Learn light did not come on during the WB learn. Is this typical? There were numerous changes to the VE tables which were tough to get to when using a NB learn and staying out of AE and PE so I assume a learn was occuring.

2) The EBL PE light was yellow instead of the typical green. What does this mean?

3) During cruise where the VE table was tuned with NB, the WB was showing 14. I was expecting to see closer to 14.7. Do I need to do some calibration? I went through the posts on installing the WB with the EBL and I think I have it correct. (I know have to change the stoich from 14.7 to 14.0 to reflect the 10% ethanol I buy - was this a coincidence?)

Thanks for your help. I do try not to post stupid questions that have already been answered. I am a road warrier and it pains me to not have the time I want to tune. At least I get to read the posts while I hang out in hotels. WIth the limited tuning I have had time to do the engine is really waking up.

RBob

iTrader: (1)

1) For the WB learn, the ECM needs to be in open loop. Can force this via the option words bits or by the closed loop enable temperature (set it high). If you saw corrections then learning was taking place. It can go in and out of VE Learn as the TPS and MAP varies (AE, DE, DFCO, etc), that you may not have seen the moving box go green.

Best for VE Learns is to hold the throttle steady. To accelerate, push down and then stop moving the go-pedal. Hold it in one place. To accel further, push down and then hold the pedal still.

2) Yellow for the PE light means the ECM is in PE mode.

3) Not unusual for the WB to report a richer AFR then the stoich value. In closed loop the ECM target is via feed back of the O2 sensor. There is a window that is targeted and it isn't always around stoich. See the sticky for the '8063/'8746/'7747, fueling logic (oor close to that). It explains the closed loop fueling and how it works.

RBob.

TMO

I read the O2 sticky several times and it was very helpful. I want to make sure I understand how to interpret the EBL output when doing a WB learn.

I have been tuning to 14.7:1 and need to change that to reflect 10% ethanol. In the sticky you say that stoich for ethanol is 9.0:1, which would result in a stoich of 14.1:1 for 10% ethanol. I have seen other sources (Car Craft) quote an ethanol stoich value of 7.87:1, which would result in a stoich value of 14.0:1 for 10% ethanol. I assume this small difference is not significant.

If I set the AFR to 14.1 I assume I will have to also change the PE values to reflect a 10% ethanol mixture. When using an AFR of 14.7 I had all the PE values set at 12.8. If I understand the 7747 ECM logic correctly I will have to set the PE values for 10% ethanol to 12.3 (12.8/14.7*14.1). This is based on my understanding that in open loop the stoich value is used in the PW calculation. I am going slow and do not want to be too lean and end up with a hole in a piston.

Turning to understanding the EBL output when using a WB, there is the "AFR" column and the "WB" column. Looking at the data log it appears the "AFR" is the commanded AFR, while the "WB" is the actual AFR. Is it correct to assume that I want to get the "WB" to match the "AFR"? My confusion comes from a comment in the sticky that when using straight ethanol which has a stoich of 9.0:1 "A WB that uses 14.7:1 as stoich will report 14.7:1 when using ethanol and at stoich even though the real AFR is 9.0:1. I am using a ZT-2. So, if the EBL "WB" reports 12.8 is it really 12.8 or is it the 12.3 I put in the PE tables?

One more question about PE values, recognizing the often quoted Grumpy comment "give it what it wants". My understanding is maximum power is at lambda, which at pure gasoline with a stoich of 14.7 would be 12.5. Why does the stock bin use a PE of 12.8? Protect the cat? And why in the stock bin do the values for PE vary depending on TPS? (I have all PE set to the same value so it easier to review the WB output.)

Unfortunately I am pretty well maxed out on FP with the injectors I am using and changing the stoich to 14.1 will mean putting in another set, which I have. I had a bad experience the last time I put in bigger injectors. What I learned is not to believe the colors or numbers on the injectors. I have three sets and had them all cleaned and flow tested and the actual was substantially different from all the values I have seen on the board. Oh well, the increase in performance is well worth the effort. The truck is sure more fun to drive.

RBob

iTrader: (1)

I'll open by stating that this whole thing is a can of worms. Grab one escapee and get back in the can and 3 more are making an exit.

The first step is change what the WB reports as "stoich." If that can't be done then stay with 14.??-whatever they use. This includes the stoich value used in the calibration, along with the other AFR based tables. IOW, if the WB uses 14.5:1 as stoich, then set the stoich AFR in the calibration to that value (yes, stoich for gasoline varies among WB controllers).

Then change the other AFR based values as a ratio of 14.5 (if that is 'stoich') over 14.7:1. There is the AFR vs CTS vs VAC table, and the lean limits. Leave the AFR vs CTS multiplier alone. Only change that as required by warmup. Not by a change in fuel composition.

Then do the WB learn based on the WB reported AFR. The difference in PW from the difference in AFR will be made up for in the VE table(s) and BPC value(s). Not much else can be done if the WB stoich value can't be changed.

However, what can be done is to use lambda. A lambda of 1 is stoich, and is based on, well, stoich, whatever that AFR may be.

The issue is that no one uses lambda, so it isn't supported in the WUD. No one wants to see a lambda value.


Cat-con protection: need to go very rich for this. Low 11's, high 10's for AFR. This is usually done in the mid-rpm to put the cat out. Then lean some from there (as the RPM increase) for power.

The 12.8:1 AFR is a generally accepted value for best power while staying rich enough to not damage the engine.

RBob.

TMO

I will need to ponder this and go back and study the sticky. I typically wait to respond in order to not waste folks time, but I do want to sincerely thank you for your response.

The ZT-2 does have the change the NB switching point, but this is not much help when using the wideband.

My goal is not to squeeze every last once of power out of the engine, but to get close, whatever that means. For me the fun is trying to understand what is going on. My 6000 pound beast will never set any speed records.

The engine runs so much better now with the EBL. I suppose if I tune to 14.7 I will not be leaving too much on the table. The one thing I worry about is going too lean at WOT. I think if I error on the rich side I will be ok.

Thanks again.

RBob

iTrader: (1)

Yes, I understand. One thing is that stoich is stoich no matter the fuel. If the WB uses 14.7:1 as stoich, it will report 14.7:1 when running stoich with gasoline, E10, E85, E100 as methanol. Fuel doesn't matter.

An O2 sensor senses stoich as stoich. AFR has nothing to do with it. It is a lambda value. A Lambda of 1 is stoich if running E10, gasoline, E80 or straight toluene.

So, when running E10, and having a WB setup that reports stoich as 14.7:1, then at 14.7:1 the AFR is really 14.1:1. Which is basically stoich for E10.

Same with the NB O2 sensor. It switches at stoich. Which is whatever it is for the fuel being used.

RBob.