95 LT-1 Idle Cell Comparison - Humidity?

**spfautsch** · 10-31-2019

I hate to keep this thread alive, but I made another discovery today that is pertinent to the idle BLM splits that were chronically showing the right bank lean and the left bank rich.

So some background - it's been rainy and cold all week and all I've been able to do is work with startup fueling and idle trims. I've been noticing the wideband maxing out lean periodically when both left and right integrators synched up for a lean swing. I've also been noticing an intermittent miss at part throttle that also seemed to briefly peg the wideband lean (presumably from raw fuel getting in the exhaust). I began to wonder if my individual trims are too extreme and are causing these problems. Today I had a bit of time to experiment with trims in open loop while trying to keep my wideband matching commanded AFR. Oddly, the individual trims seemed to make very little difference when I added or removed from one bank. But while I was doing that I noticed that when I forced AFR above 14.5:1, after a few minutes the right side O2 would start trending down around 150mv and then eventually flatline at 40-50 (this is with BLMs reset to 128).

Then, as I was looking over kur4o's nice new controller window it occurred to me I've never tried moving EOIT. Sure enough, when I got to 129* things smoothed out somewhat. I then switched it to closed loop and to my amazement there was only a 2 point split. Toggling the EOIT override while in closed loop I witnessed the BLM splits come back and then go in unison with the override. So I suppose my lean condition on the right wasn't an exhaust leak or so much an actual lean condition as it is raw fuel getting into the exhaust during overlap. So I guess I'm going to try using 129* EOIT and start all over with individual trims and see what happens. I expect my off-idle fueling will get way out of whack due to loss of wall film.

**spfautsch** · 10-31-2019

kur4o: after a bit of experimentation, I think your calcs are inverted on the display of the EOIT slider value. I think it should be:

Code:

void controller::on_slider_endofinj_valueChanged(int value) { //new end of inj
  // upd. text display always
  int degrees = (double)value * 5.625;
  ui->display_endofinj->setPlainText(QString::number(degrees,'d',0)+"*");
  // upd. mode4
  if(ui->check_endofinj->isChecked() == true) {
    control->m4_comm_endofinj(true,ui->slider_endofinj->value());
    update_m4_raw_display();
  }
}

Edit: disregard that - it's pretty superficial. I'd overlooked the ATDC label and I hadn't thought about EOIT terminology in ages.

So what I was assuming to be 129* BTDC was actually 596* BTDC. So my testing wasn't reducing EOIT but in fact increasing it by 56 degrees.

Whatever the case, this is promising news and falls in line with what the LS guys were saying about increasing EOIT from "60 to 61-64".

This has absolutely no relevance to intake valve closing on the cylinder with the active injector. I'll have to do some degree wheel work, but I suspect it's more closely related with having an adjacent (fuel scavenging) cylinder on it's intake stroke while fuel is being sprayed on the "current" cylinder.

Whatever the case, increasing my 0x12df2 table values in the 44c and greater cells from 0x60 (540* btdc) to 0x6a (596* btdc) has reduced my idle BLM splits from 10-16 to 1-4.

I'll post more analysis when I figure out the whys and hows.

Edit: After quite a bit of hypothesizing I'm still not sure why this works. The only thing I can come up with is that perhaps it moves injection to a point where fewer left bank cylinders are on their intake stroke while even bank injectors are firing. Fuel being robbed by another on the same bank won't cause a BLM split.

**kur4o** · 10-31-2019

You still amaze me at discovering more stuff through experiments. I never thought about possible blm split by EOIT target. What you have done is move the target earlier to the actual intake valve opening. So there is more time for the fuel to turn into vapor. Stock settings of EOIT takes into account normal operating engine temp at 100-110C*, now when you run it at 80C* it takes considerably longer for the fuel to evaporate.

One reason this can happen is one of the head runs at substantial lower temp while the other is hotter. Not even temp distribution accross engine. The colder side can`t evaporate all the fuel and there is some left unused by the cylinder, during combustion the left over fuel evaporates and is robbed by adjacent across the board cylinders leading to one side running leaner and the other running richer.

Of course this is only speculation.
For the sake of confirmation you can heat the engine upto 100C* and confirm or deny the theory.

I also been considering improving the code of EOIT target by adding more tables, like MIN EOIT vs rpm or closed throttle EOIT table.
Think about it and let me know if there will be any benefit of doing it.

The setting in eehack is *ATDC, which is correct. If you need it at *BTDC just substract the result with 720*.

The shorcuts can get even better if you have some time to do it. Adding some more shortcuts like D+1...8 to set drive cyl and I+1...8 to set at idle cyl, D+0 and I+0 unset, and some more for enable and disable, maybe ctrl+I and CTRL+d might do it, I am sure you will find even some better combination.

Last time I played with the cyl trims controls it sucked really with that mouse and slider I even considered changing the design of it. But with some keyboard shortcuts it will play really nice.

I had a ps pump failure and abandon tuning so far, The last time I managed to run it I discovered that accidentally I have disabled the trims and they were set at 1 all the time, invalidating my last attempts. With 1 for trim the starting was a little weird sounding but still started almost good with no hesitation. When I enabled the trims it started again with healthy sound. Maybe your no start condition with off the chart idle trims can be the result of crank VE table not set right.

I also discovered that the injectors definitely flow more that my initial settings. I managed to increase the fuel flow scalar with much positive results. Also played with the warmup spark scalar table. At 20C* it idles best at 14 degrees and slowly recovering to 23-24 degrees at 50-60C*. Even 1-2 degree change at 30C* coolant change the sound alot. Still no clue how to tune it the proper way other than feel and smell.

**spfautsch** · 11-01-2019

Another thing that may be a factor is that the exhaust system is asymmetric between the header collectors and the x-pipe. One side might be generating more exhaust scavenging than the other at idle speeds. In working out the different valve events looking for ideas I found 596 BTDC moves the injection event (at 800 rpm it's only 3 degrees for ~2ms) so it's almost out of all overlap scenarios. But this may be completely irrelevant. I'll definitely try getting it hotter to see if your idea of uneven cooling could be a factor.

The only reason I can think of for having the need for more EOIT controls is if this change causes a BLM split at part throttle, and it will be a few days before I'll have a chance to drive it. I'm hoping to rework the closed individual trims tonight, but I'll probably get roped into handing out candy.

I'll look at the possibility of adding those key accelerators - I haven't tried modifiers like ctrl, alt or shift so no idea how involved that, or using a normal key like 'i' and 'd' as a modifier key will be.

**Terminal_Crazy** · 11-01-2019

Similar results to me then, extending the time the fuel sits in the port or forcing it further down the port so it has less chance of being sucked back out?

Have you tried a sweep test.
This was mine last year.
I think the LH inj pw staying the same is an issue I've had with flashing & logging with different versions.Never quite pinned it down.
EOIT can make quite a difference to the splits. I'm currently running at #63.
2018-12-13
Did another EOIT spread degree test with odd figures .........

Test B at 86+øC

Blm's running on pcm setting of &66 120 122
log went lean/weird around 74øC to 75.5øC 68C eoit = &50 80C=66
Left bank richer - rhs longer inj time ?????????????????????????????????

start 1200 Idle Fast
Time log ø table blm's blm's Inj PW SPLIT SPLIT

685 7170 146 66 120 122 1.79 1.79 pcm setting &66 + 2

832 8764 186 5F 115 125 1.79 1.79 +10
1110 11681 208 5B 113 130 1.77 1.94 +17
1225 12875 231 57 106 130 1.77 1.95 +24
1400 14711 253 53 104 130 1.77.1.92 +26
1540 16180 276 4F 99 134 103 139 1.75 1.95 +35 +37
1715 18010 298 4B 103 137 99 145 1.77 1.97 +34 +46
1890 19843 321 47 98 137 99 145 1.77 1.95 +39 +46
2030 21313 343 43 98 137 99 145 1.77 1.97 +39 +46
2135 22413 366 3F 97 137 99 145 1.77 1.97 +40 +46
2275 23881 388 3B 99 143 100 150 1.77 1.94 +44 +50
2590 27180 411 37 98 134 100 144 1.77 1.92 +36 +44
2730 28647 433 33 96 134 100 144 1.77 1.91 +38 +44
2870 30109 456 2F 96 136 100 144 1.77 1.92 +40 +44
3010 31574 478 2B 104 136 97 144 1.77 1.92 +32 +48
3150 33038 501 27 101 136 101 138 1.77 1.88 +35 +37
3255 34143 523 23 104 135 106 132 1.77 1.83 +31 +26
3465 36343 557 1D 104 132 104 132 1.77 1.82 +28 +28
3605 37807 579 19 104 132 110 132 1.77 1.85 +28 +22
3710 38908 602 15 99 132 99 132 1.77 1.86 +33 +33
3850 40373 624 11 96 139 104 132 1.77 1.83 +43 +28
4025 42209 647 0D 99 136 102 132 1.77 1.89 +37 +30
4200 44042 669 09 103 131 107 132 1.77 1.85 +28 +25
4340 45510 692 05 103 131 104 132 1.77 1.88 +28 +28
4480 46979 714 01 103 131 104 132 1.77 1.82 +28 +28

Restart at end of table
4585 48077 96 6F 107 118 111 120 1.75 1.66 *INJ PW swaps* +11 + 9
4725 49541 118 6B 116 121 116 120 1.83 1.56 + 5 + 4
4865 51005 141 67 118 121 119 120 1.77 1.60 + 3 + 1
4970 52105 163 63 118 117 119 120 1.77 1.63 - 1 + 1 <-<-
5145 53935 186 5F 117 117 119 120 1.77 1.66 0 + 1
197 5D 108 125 111 122 +17 +11
5285 55938 208 5B 107 130 102 139 1.77 1.82 +23 +37
5565 58321 231 57 107 129 105 139 1.77 1.79 +22 +34
5635 59054 253 53 104 129 101 139 1.77 1.85 +25 +38

Mitch

**spfautsch** · 11-01-2019

I haven't tried a complete sweep test yet, finding that my splits changed immensely was mostly by accident. It's been ridiculously cold this week and I've had limited time to work. When I have it's in the garage with the door open so the gas fumes are tolerable, so I haven't been able to be as methodical as I'd like.

Last night I worked on closed throttle individual trims. One of my classmates showed up to trick or beer me as I was working so I had to stop, but I was basically back at stock trims with just a few minor changes and BLMs were 127 left and 129 right. I'd really like to get this nailed down so I can also nail down startup fueling, but as it works everything seems to be inter-related. Out of curiosity, I did briefly try moving EOIT to well after my exhaust valve closing @ 323 BTDC but the BLMs went crazy. Once I'm more satisfied with individual trims I'll give a full sweep test a shot.

My theory on why this is working is based on the idea that fuel scavenging inside the intake only edit: (or, primarily) happens while an injector is spraying, and once the fuel is down on the back of the intake valve and port bowl the scavenging effect is dramatically reduced because the air from the idle feeds can't reach it there. I don't think it's related to having more time for the fuel to boil into vapor, but I do intend to test because my theory could be complete nonsense. I attached the worksheet I built to help visualize the relationship of all the different events.

It's extremely puzzling that your LBPW never drops below 1.77ms. I'm curious - what values do you have in 0x126d5 and 0x126d7 (min injector pulsewidth)?

**spfautsch** · 11-03-2019

Hey Mitch would you mind recapping your methodology when you did the sweep tests? Did you reset BLMs when you moved EOIT? How long did you let it idle before recording the BLM split, or did you average?

I did a sweep from 540 to 624 BTDC this morning and in the process noticed my BLMs seemed to inversely follow coolant temp. I have a 71c thermostat and fan on setting was at 82c so coolant temp was varying by about 4c. At 83c trims were about 2-3 and at 79c they were about 4-7.

So I decided to try bringing temps up by digging out my 82c thermostat and dropping it back in. I had to bump fan on temps up some so they weren't running on high all the time. After a short drive the coolant temp at idle was steady at 91.3 with fans contant on high. I did another brief (i.e. not well documented) sweep test and found nothing compelling. Splits averaged out to about 3 but maxed at 7. I'm planning on doing another thorough sweep tomorrow.

This is all with almost stock individual cylinder trims. Overall it's running much smoother than when I was running radical trims trying to compensate for a ~12 point BLM split.

In the midst of this I'm pretty sure my wideband sensor is toast. In closed loop it's reading pegged at 16.39:1 (5v) quite a bit. Last week when air temps dropped, on the last leg of the commute the wideband was flatlined at 0v (11.39:1) the entire 62 mile drive. I thought the fuse powering the controller might have blown, but it wasn't. After installing the 82c thermostat I took about a 10 mile drive and had a chance to open it up for a few seconds where commanded AFR was 12.5:1, and the wideband was flatlined through the whole PE event, then went back to reading really lean. Curious if anyone else has noticed this type of behavior in cooler air temps, or if I should start looking for a new Bosch sensor.

**Terminal_Crazy** · 11-04-2019

Hiya
Car warmed up >86C
I started to reset BLM's after the first few, so went round the table again at the end.
I basically logged until the BLM's settled (about 1000 logs minimum between changes)

I'm currently waiting for my Y pipe for the long tubes as I've just found out my mate can only bend 63mm pipe on his pipe bender.
Then I'll be looking for a Dual Wideband.

Mitch

**kur4o** · 11-04-2019

Originally Posted by spfautsch

the wideband was flatlined at 0v (11.39:1) the entire 62 mile drive. .

It looks like a toast. Or it could be the controller. Are you running 4.2 or 4.9 bosch sensor. One of them was prone to early failures due to controller. I have 4.2 and it experienced alot of abusing[including coolant fouled and cleaned with acetone] and still works, not sure how acurate but it works. They should be pretty robust and last long since are oem used in turbo VAGs setup.

On the blm split. I am running different lenght tubes upto y and the sensors are at different lenght from the heads and still haven`t experienced heavy blm split. Actually they are pretty close off idle 2-4 points difference, with untuned off idle trims. At brief idle CL itempts I made I had 1-2 points only.

When you change settings look for at least 1 minute wait time for them to take effect, even changing the EOIT target takes some time, in the code there is smooth ramp out routine that makes it really slow.
If you find that there is a need for different target for idle and off idle vs rpm conditions, I will add the new tables in the code.

Spray pattern and lower than rated fuel pressure for the injectors could affect blms. Not sure how but I read somewhere that ls1 injectors had different spray pattern.

I have one theory how fuel robbing works. The path of the air is from the adjacent feed hole cylinder through the plenum, that way it can suck left over fuel. The path from other than adjacent cylinders will be too long for the fuel mix to travel. This effect can also lead to slowly filling the plenum with fuel vapors over time, making the mixture richer with longer idle events. Than can explain different behavour with supposedly prefectly tuned engine.

I didn`t get that deep in engine rotation, but if there are more than 1 cylinders sucking air at the same time like overlapping open intake valve events. Add to this the big cams overlap egr like effect, pushing small amounts of exhaust gas in the intake plenum and the picture gets worse.
If the cam you have opens the intake valve while the exhaust stroke upward cylinder movement is not finished, you are doomed for the perfect tune failure. Just get it close enough. You can always cure some blm splits with changing L and R swing voltages.

These are from stock ybody auto
L R
460.20 460.20
389.40 389.40
442.50 442.50
460.20 442.50
460.20 442.50

Vs stock ybody manual
L R
460.20 460.20
380.55 380.55
380.55 380.55
380.55 380.55
380.55 380.55

**spfautsch** · 11-04-2019

I hooked up the serial cable to the wideband this morning and at cooler ambient temps it's giving an error 8 during warm-up. So it seems the sensor is boned. It's a 4.9. The troubleshooting guide says it could be getting too hot during PE events or the sensor is damaged. I think the heating element is burning out due to cold ambients.

Car runs a bit different with the 82c thermostat. I'm seeing a bit more knock above 2400rpm but that doesn't worry me a lot right now. I'm just concerned with what it will do during the summer months. The high today here was 16c and the fans basically ran on high all the time to keep coolant temp under 100c. Unfortunately no-one seems to make a 77c or 79c thermostat in this size so I don't think there will be a happy medium.

After some testing yesterday, I reverted to essentially stock individual trims. I added a couple points to #1 at closed TPS since I enlarged that feed hole, and added a bit to #6 which is quite a bit rich in the stock tune and I noticed my balance tests showed it seemed to be pumping the strongest at closed TPS. I don't know if anyone's noticed, but at part-throttle the base Y-body tune takes a lot of fuel out of #6 so it goes from way lean at closed throttle to way rich at part. Go figure. Low-speed cruising is good here, so I'm not going to make many changes. However, I'm somewhat baffled as to why if I have a 3 count split at idle, and add 1 to the lean side and remove 2 from the rich side, why that doesn't "cure" the split. But it doesn't. I suspect its just the nature of the cam.

I did another EOIT sweep from 523 to 624. I noticed another variable that probably explains why I'm noticing splits increase with idle time - IAT. After a short drive to warm it up for the test, when I pulled in the driveway with EOIT in the tune at 579 BTDC it idled for 2-3 minutes at 128/130 (timestamp 1500).

My process was to change EOIT then reset BLMs, then log for 100 seconds. I noted the timestamp at each change, and recorded BLMS and other relevant data after 99 seconds. During the log my IAT climbed from 32c to 44c. I suspect this is relevant so I'm hoping to reproduce today's test with a fan or something blowing cool air near the air box.

Code:

ts  eoit lbl rbl iac ect afgs split
1500 579 128 130 27 91.3 8.11 2

1600 523 118 141 28 90.5 8.17 23 < iat @ 32c
1700 528 120 139 29 90.5 8.27 19
1800 534 126 134 29 90.5 8.19 8
1900 540 126 133 30 90.5 8.28 7
2000 545 127 133 31 90.5 8.37 6
2100 551 127 132 29 90.5 8.04 5
2200 556 128 133 30 90.5 8.20 5
2300 562 128 133 30 90.5 8.16 5
2400 568 128 134 31 90.5 8.20 6
2500 573 129 134 29 90.5 8.16 5
2600 579 129 135 29 91.3 8.09 6
2700 585 129 134 29 91.3 7.98 5
2800 590 128 134 29 91.3 8.13 6
2900 596 131 135 28 90.5 8.02 4
3000 601 131 135 28 91.3 7.93 4
3100 607 132 136 26 90.5 7.75 4
3200 613 131 135 27 90.5 7.86 4 < iat @ 44c
3300 618 129 136 26 90.5 7.78 5
3400 624 129 136 25 90.5 7.75 5

As you can see there's no magic value here - the only thing that seems relevant is that after 590BTDC the left side goes lean. Otherwise it seems like I want to be between 613 and 596. So bearing in mind that lower coolant temps need more time for evaporation, I did this with my EOIT table.

Code:

A short drive with these settings showed about a 5 point split in BLM cell 2, and less everywhere else. I think I'm going to drive this tomorrow or the next day weather permitting and see what happens. If this is as good as it gets I'm happy with it - it runs very well. My clutch isn't quite able to handle 2nd and 3rd gear under full throttle.