Couldn't leave well enough alone. Again. Damn u RBob

So I started playing w the IB correction for V although motor was running well.
But I did have this bathtub curve in the VE tables. Never was able to get the
Offsets for the Accel #23 injectors, so I thought what the heck. I'll be putting the car away for the winter next week. Let me see what happens if I bump the bias 10%. Predictably, the BLMs were lowered. But what I didn't expect was to see that the L/R bank BLMs also were much closer to each other than I had ever seen them before. They tracked very closely w each other. I decided to see how far to go w the IB, and basically bumped the IB to double of what it was at 14.4, then added that same amount to lower voltages. Now the BLMs got pegged at 115. Its taking me 3-4 Learn sessions to start approximating a good fuel curve. The bathtub is beginning to shallow out. I suspect that with the BLMs getting much richer, I must be on the right track in terms of what the IB should be for these injectors. At the same time the VE% was coming down.

So any thoughts on:

1. A more accurate IB will have the left and right BLMs more closely aligned and,

2. If I bump the IB and I see it going richer, I must be headed in the right direction for a more accurate IB table for these injectors.

 

Several Learns done and now the BLMs are beginning to come into shape. The
"Bathtub" is melting away. It has takes 3-4 learns before BLMs began getting into a workable range. Hoping to really hone this in the next few days and before car goes up for winter. Need to play w AE as the VE goes goes through a significant change. Some stumble on tip in especially right after decel. Seems like motor "loads up" and then goes lean to clear things out.

 

Learns keep taking fuel out. Car has also developed a stuttering in the 1600-2200rpm range with MAP between 30-40kPa. I can watch my WB go very rich then I depress the accelerator a bit, WB goes full lean, then it clears up.
Also looking at the datalog, I am noticing that the right side O2 sensor will intermittently go to 0v. Sometimes for just a few frames, other times long strings of 0 while the left side doesn't show anything like that. There also doesn't appear to be any pattern, ie at certain RPM or TPS position. What would be the consequence of this happening? IOW, what would I see the motor do?
LEARN stays on although I have noticed that it will fall out of C/L, then back in but I don't see the correlation on the datalog.
I think I may have overdone the Injector Bias, and am likely going to be dialing it back.

Thoughts?

 

Doubling the IB at 14.4V and so on is quite a change. It will affect smaller PWs much more then larger PWs. With depressing the go-pedal in the above range, look at what the INT is doing. I've seen this where the INT drops from being rich, then as the AE runs out the engine goes into a lean sag.

A period of the O2 reporting 0 will cause the ECM to increase the INT, followed by the BLM. Does the engine sag at this time, if it doesn't there may be more to it then that side going truly going lean.

Learn and closed loop are two different things. Many times they even have different CTS enable parameters. Closed loop needs to have an active O2 sensor signal. If it stops switching for 20 - 30 seconds the ECM will usually drop out of closed loop.

RBob.

 

RBob,

Thanks. I've probably overcooked the Injector Bias, but hey it's a learning experience and that's what we're here for.
I'm wondering if the O2 signal dropping out is responsible for the right side BLM dropping to 115. Then the question is why the signal intermittently drops to 0.
Maybe something in the harness? The O2 sensor has only a few thousand miles on it. I went back to some datalogs I had done prior to any changes I made to the IB and found the same kind of intermittent drop off. So this has been going on for a while. Hmmmm.

 

It may be the opposite, that the low BLM is causing the O2 to report lean. A low O2 will drive the BLM up.

RBob.

 

RBob,

I see what you are saying. I have watched the BLMs on the right side drop while sitting there at a steady cruise as an example. Its a bit more pronounced at idle.
Uploaded a portion of the datalog I took yesterday. This segment is indicative of what I was seeing. Interestingly tho, going back to previous logs, I found similar pattern so it doesn't appear to be a function of the recent changes I made in the Injector Bias. The log is a zipped text file. You can unzip and then use .xls to read it as a comma delimited file.

 

RBob,

given that I am seeing the right side O2 dropping out in logs taken prior to the IB changes, I will be investigating the O2 and the harness. Installing headers on the LT-5 required a harness extension for the O2. I'll be checking into that and see if I am getting some
kind if signal loss or short.

 

Looking at previous logs and I don't see any discernible pattern. Its seems to be a question of chicken or the egg. It doesn't appear to be dependent on TPS, coolant temp, MAP. I can see segments of the log where O2v drops to 0 and the INT starts to rise within a frame or two after that. INT usually in the 118 range then starts to climb into the higher 120's.

 

In trying to find the right Inj. Bias for the 23# Accels I have, I think I have settled on 20% higher than what the IB is for the stock Bosch injectors on the LT-5. My observation in coming up w a more accurate IB is that the BLM split L/R banks seems to be much smaller. It still appears to diverge at idle but the spread isn't what it was. However, above that point the BLMs track very closely with a +/- of 4 from 128. Actually the avg turns out to be 133.4/125.6 or an average BLM of 129.5. This average includes idle which is about a 136/120split, so you can see that cruise is much closer. Slightly lean but I think that makes for a mellower exhaust note. Also, getting to the right tune happened much quicker. I've gone through maybe 6 iterations and now at the point where we are trading the constant .39 back and forth.Once your there, no sense in doing the seesaw.
The motor runs smoothly and doesn't have the blub blub blub note form the exhaust at low rpm/higher MAP. Summarizing it looks like chasing a more accurate IB has the advantage of:

1. Tightening the spread between the L/R bank BLMs. For me, this would also be a big argument for wanting to run C/L. In C/L the O2s are working to bring
both banks into tighter alignment in terms of fuel mixture. Without the O2s, as in O/L, you'll be working w the optimization of whichever bank you've decided to put your WB into. And someone tell me if there's a MASK ID out there that has VE or LV tables for each bank? That would be a bear. Got my hands full w 4 VE tables right now. Granted there will still be some variation due to injectors and even the O2 sensor itself, but at least you have an ECM doing self-correction. Anyway, maybe a separate thread on this topic.

2. Makes getting to the right tune considerably quicker.

My only other question is whether to bother w a bit of smoothing or just leave well enough alone.