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I've spent quite a bit of time doing VE learns (EBL P4) and get pretty consistent BLMs. Then turn back on the EGR,CCP etc and then at certain areas they are skewed by EGR(leaner) or CCP (slightly richer). So if it looks at the last BLM before going into PE mode is it still better to adjust VE tables with smog functions off?
I've spent quite a bit of time doing VE learns (EBL P4) and get pretty consistent BLMs. Then turn back on the EGR,CCP etc and then at certain areas they are skewed by EGR(leaner) or CCP (slightly richer). So if it looks at the last BLM before going into PE mode is it still better to adjust VE tables with smog functions off?
Is there a way to not have the ECM make PE adjustments based on the preceeding BLM value?
Thats what I did in my 8D code. Keeps the PE AFR more consistent.
Other than allowing the integrator to fluctuate, is there any difference between that and plain ol' open loop?
none that I can determine. Locking the BLMs negates any change to the VE table which is where I do my WOT tuning rather than the PE table. VE is more granular.
So if it looks at the last BLM before going into PE mode is it still better to adjust VE tables with smog functions off?
In PE, it will lock INT at 128 but will keep the last BLM recorded in the cell, unless BLM is lower than 128, than it'll lock BLM at 128. Personally, I don't activate BLM anymore with a speed density tune. Just my personal preference. BLM can be close to 128 on average but, BLM cell max/min can still swing a lot. It all depends on your cell boundaries and BLM update rate/step. I like turning off BLM and tuning with INT only. I always tune VE with normal driving condition, includes "smog functions" enable.
I like to divide BLM cells in a way that WOT cells do not mix with CL cells. I will dedicate Cell 12-13-14-15 to WOT (NA) with MAP greater than 90. I will program PE mode to kick in only when MAP is greater than 90 as well. That way, when in PE at WOT, BLMs are always at 128. This way, it gives me a consistent 12.5-12.8 AFR at WOT across the RPM band. I don't have to worry about BLM screwing things up.
I also deactivate Stay Alive Memory (SAM), so when on cold start-up, OL warm-up is consistent. BLM always reset to 128.
Now this is with '730 ecm. I don't know if the EBL has more cell definition. The stock '730 is limited to 15 BLM cells. That makes BLM inaccurate base on my experience.
When I was tuning my 84 Xfire using a 7747, I would lock BLMs and use the INT instead since the BLM update rate on the 7747 was very low. The INT updated more frequently. Then I converted over to RBob’s EBL.
Last edited by Dominic Sorresso; 12-19-2023 at 09:37 PM.
When I was tuning my 84 Xfire using a 7747, I would lick BLMs and use the INT instead since the BLM update rate on the 7747 was very low. The INT updated more frequently. Then I converted over to RBob’s EBL.
I do the same with '730 $8D. I turn off BLM and extract INT data instead. I export data into a custom excel work sheet that averages the INT values. The averages are broken down into smaller cells that correspond to the VE tables. The worksheet corrects the VE table automatically based on my parameters. It works like a charm.
I do the same with '730 $8D. I turn off BLM and extract INT data instead. I export data into an custom excel work sheet that averages the INT values. The averages are broken down in smaller cells that correspond to the VE tables. The worksheet corrects the VE table automatically based on my parameters. It works like a charm.
Interesting approach... tuning the VE tables off the INT.
What I've done is take the TP RT BLM history and display the history average. Then copy that into my own VE tuning spreadsheet. I've had pretty good luck with that.
What Ive also done is change the calibration such that the BLM won't change unless the INT moves more than 10 points in either direction (the factory value is +/-5). I've also slowed down the INT response time to 2 seconds.
This seems to help keep the ECM from overreacting to transient AFRs associated with accelerator enrichment.... given how large an initilal shot the Miniram needs. I really only want the ECM correcting fueling during steady state operation. My AE decays out 40-50% faster than the factory 8D settings, so it's only there for a very brief period of time... I just need to ECM to butt out for that... lol.
I know you can also throw the flag for "Reset INT when AE is active", but for some reason that flag produces a more laggy feel to the throttle and I don't fully understand why.
Awesome wealth of knowledge on here! I emailed BobR-the EBL does not have a flag to lock BLM at 128 in PE. I was looking at that as the simplest/easiest solution. Next I will do VE learns with smog functions on-the conditions for egr on etc should stay consistant so I'll see how that works out. I've had it lock at BLM 140 as it enters PE and even though PE AFR is set to 13.0 the wideband will show 10.5. I can't just run open loop as I have to keep closed loop for smog.
Regardless of the BLMs, keep in mind, the commanded AFR is may not necessarily see on the WB. Other things can cause variation like how the injectors are flowing relative to the flow rate value you entered, etc. You would basically adjust the commanded up or down to get your actual where you want it.
That said, yeah if you're going into PE with a 140 BLM, then I believe your AFR would get a "fudge factor" of 140/128 = 1.09 applied by the ECM to richen it up. So that would account for some of your observed discrepancy. If you're commanding 13.0, then after the ECM got done with its adjustment, it would override you and command an ~11.9. The rest of the difference is probably due to other factors I alluded to.
Following what @ULTM8Z said, here's the calculation before INJ PW voltage & low PW adjustments:
As you can see:
if you increase commanded AFR (less fuel), you need to increase VE% to obtain same INJ PW
if you increase INJ Flow rate, you need to increase VE% to obtain same INJ PW
if you increase ENG Cyl. Vol, you need to decrease VE% or increase Commanded AFR to obtain same INJ PW.
So the ECM does not know what's what. All it knows is making calculations based on user input (Commanded AFR, ENG Cyl. Vol, VE and INJ Flow Rate) and sensor input (MAP and MAT). RPM, CT and TPS play a role for look-up in tables.
Commanded AFR is determined depending on different states:
Open Loop
Highway Mode
Closed Loop
Power Enrichment (PE)
So this Speed Density (SD) EFI system is a gross estimate of the amount of air in each cylinder, the amount of fuel needed and how long it should open the injectors in batch (not sequential). All that managed by a 1980's era slow computer with limited accuracy.
On top of all that, the INT tries to correct the estimate, in closed loop, to accomplish stoichiometric combustion, by using 1 non heated O2 sensor on 1 bank!!!! In PE, the ecm is shooting blind.
I would definitely make sure the BLMs are at 128 at WOT at all times with what ever method you use. Also, make sure you always use the same gasoline from same gas station. If you introduce ethanol in the mix, your real AFR at WOT could vary. Example, you tune with no ethanol, then introduce a full tank of gasoline with 10% ethanol. Your AFR at WOT will get leaner.
So this Speed Density (SD) EFI system is a gross estimate of the amount of air in each cylinder, the amount of fuel needed and how long it should open the injectors in batch (not sequential). All that managed by a 1980's era slow computer with limited accuracy.
That said there is still an impressive amount of functionality built into the 8D code. Particularly on the AE for dialing in a manifold like the Miniram.
Following what @ULTM8Z said, here's the calculation before INJ PW voltage & low PW adjustments:
As you can see:
if you increase commanded AFR (less fuel), you need to increase VE% to obtain same INJ PW
if you increase INJ Flow rate, you need to increase VE% to obtain same INJ PW
if you increase ENG Cyl. Vol, you need to decrease VE% or increase Commanded AFR to obtain same INJ PW.
So the ECM does not know what's what. All it knows is making calculations based on user input (Commanded AFR, ENG Cyl. Vol, VE and INJ Flow Rate) and sensor input (MAP and MAT). RPM, CT and TPS play a role for look-up in tables.
Commanded AFR is determined depending on different states:
Open Loop
Highway Mode
Closed Loop
Power Enrichment (PE)
So this Speed Density (SD) EFI system is a gross estimate of the amount of air in each cylinder, the amount of fuel needed and how long it should open the injectors in batch (not sequential). All that managed by a 1980's era slow computer with limited accuracy.
On top of all that, the INT tries to correct the estimate, in closed loop, to accomplish stoichiometric combustion, by using 1 non heated O2 sensor on 1 bank!!!! In PE, the ecm is shooting blind.
I would definitely make sure the BLMs are at 128 at WOT at all times with what ever method you use. Also, make sure you always use the same gasoline from same gas station. If you introduce ethanol in the mix, your real AFR at WOT could vary. Example, you tune with no ethanol, then introduce a full tank of gasoline with 10% ethanol. Your AFR at WOT will get leaner.
This should be a sticky. I've had time to work on adjusting the VE tables and tried adjusting the injector sizing also. It is surprising how much difference it makes in the wideband reading vs commanded AFR depending on if the BLM happens to lock at <_128 vs even just slightly above 128 when it goes into PE mode. I am definitly going to bias the VE tables so it is always slightly below 128.
This should be a sticky. I've had time to work on adjusting the VE tables and tried adjusting the injector sizing also. It is surprising how much difference it makes in the wideband reading vs commanded AFR depending on if the BLM happens to lock at <_128 vs even just slightly above 128 when it goes into PE mode. I am definitly going to bias the VE tables so it is always slightly below 128.
From experience, a BLM of, let’s say 137 does not translate into add 7% to VE (137/128). I usually start with around 50% of that, so 3% in our case. Don’t forget MAT plays a role. A heat soaked MAT will lean out fuel at WOT PE depending on your tune.
But again, I did away with chasing BLMs on $8D. BLM is disabled and I run on INT only. More accurate for VE tuning in my opinion but most importantly better consistency.
I do the same with '730 $8D. I turn off BLM and extract INT data instead. I export data into an custom excel work sheet that averages the INT values. The averages are broken down in smaller cells that correspond to the VE tables. The worksheet corrects the VE table automatically based on my parameters. It works like a charm.
Trying to fine tune the VE tables going off INT with a locked BLM reading info from older non active threads where I was able to at least find the formula for INT to be
New_VE = Old_VE x (1+((128-INT)x.0034))
Is there a worksheet available for locked BLM INT tuning using tunerpro's INT log's
Trying to fine tune the VE tables going off INT with a locked BLM reading info from older non active threads where I was able to at least find the formula for INT to be
New_VE = Old_VE x (1+((128-INT)x.0034
ummm!
Example using this formula
Average INT =132
Old_VE = 80
132 = lean = need to add fuel = need to increase VE
New_VE = 80 x (1+((128-132)x0.0034))
New_VE = 80 x 0.9864
New_VE = 78.9
Does not look like the formula is right. It removes fuel instead of adding!
I proposed:
New_VE = Old_VE * ((((INT/128)-1)*0.5)+1)
You can change 0.5 for 0.25 or 0.33 if you want. The point is to avoid chasing your tail by correcting VE based on 100% avg INT. I like starting with 50% of value but sometimes I’ll use 25% to fine tune.
Are you using TunerPro? how are you breaking down the INT data to VE cells?
When I export INT data to a .csv file I get the giving INT data based on the time of the log, with the available BLM spreadsheets from the stickied tuning guide they are using tunerpro's history tables
Yes you are correct New_VE = Old+VE x (1 + ((INT - 128) x .0034))
Last edited by STEALTHWRAITH; 02-17-2024 at 01:20 PM.
Are you using TunerPro? how are you breaking down the INT data to VE cells?
That is the million dollar question! I'm doing it my way but I am sure there are other ways. It took me many, many, many hours to come-up with this system. I have and advanced knowledge of Excel software, which really helped. So here's a brief summary:
I export TunerPro's data into a .csv file
I clean-up and organize the data the way I want it. It can be a tedious process, specially when you have lots of corrupt data. I use filter functions to analyze max/min on each column that I keep. I get rid of bad data. I also remove any open loop, PE, DFCO, cold engine and other irrelevant data for VE close loop tuning.
I export the data into another custom made Excel database.
Through Excel's custom programs and calculations, AVG INT values are populated into a table that mirrors my VE table in the tune. I have to interpolate part of the VE table corrections. Then, It will automatically generate a partially corrected VE table based on the data.
I just copy and paste the new VE table into TunerPro.
I go out, datalog, rinse and repeat.
I also datalog real AFR from a gauge, to keep an eye on things.
Initial AVG INT generated by Excel, mirroring the VE table. At the top I also get the AVG INT by BLM cell.
Number of counts (frames) per BLM cells and also by VE table cells. Tells you where the engine spend most of its time.
AVG INT for cells with 10 counts (frames) or more. This concentrate the correction only on cells that were meaningly hit. Sometimes I use 25 instead of 10.
Proposed % correction to VE. That is a 50%, sometimes I use 33% or 25%. This is used to generate the new VE table. Once VE table is generated, I have to smooth it out to fill some blanks.
The AFR gauge averages
Long, boring, and tedious process using an antiquated system not very accurate.
IMO, you don't need BLM or INT to be exactly at 128. Chasing this can become obsessive and accomplishes nothing really. It's way overrated. As long as the ecm is capable of being close to 128, that's good enough. +/-8% error is more than acceptable for me. I don't really care much about close loop operation. As long the ecm does not have to swing the INT too much and the AFR results are as close as possible to 1.0 lambda (14.7 in my case). Sometimes, you might have to modify the 02 sensor voltage windows to get the AFR corrected even if you get a nice 128. Also, at idle, I find it's better to richen the AFR to smooth out things. This can only be accomplished by modifying 02 voltage windows.
What really matters is the WOT operation. ECM goes blind during power enrichment (PE). You need an AFR gauge and a dyno to tune AFR and SA, if you want to extract the most out of your engine.
Thanks for your time posting all that, yes it gets obsessive, when you say 8% do you mean 8% of each other or 8% from 128
For example from this DL my highest BLM is 137 and lowest 120 the INT sees 114 and highest 145
Is a BLM of 138 and INT of 128 acceptable 8% difference
Another reading of BLM 133 and INT 141, both are within 8% of each other but now the INT is over 8% from 128
When I say 8%, I mean 118 to 138 max/min for BLM, if you use BLM. You can have an average BLM of 128 with extremes at 148 and 106 for example. You'd rather have an average BLM of 134 with max of 136 and 126 for example. Problem is the BLMs are average by Cell# which makes it hard to pin point where the problems are. You can also have better BLM just by slowing down the update rate (cheat trick).
As far as INT, it can swing much more. It is more accurate though. You also have to use the average. The ECM makes the INT swing all the time. If you observe the INT on steady cruise, it just swings back and forth. That's normal. So you have to use average which will give you some sort of swing point. You want it as close as possible to 128 on average.
Again, I would not go too crazy about that stuff. They swing wildly from factory anyway.
UPDATE:
Problem with this whole BLM non sense is it's divided in large BLM cells. So you might ride an area of a cell that is lean which makes the INT react to 145 for example and update the BLM from 128 to 136. Then, you move to another area of the same cell where it's rich, so the INT has to swing hard to let say 90 because the BLM was last locked at 136 and needs to come back down. It's a wild swing ride. I hate it! That's why I disabled the BLM. Now all I have to deal with is the INT.
Once I have a new VE calcs I look at areas that were not changed using TP graphing. I try to “smooth” areas in between sections that were changed. Smoothing makes a difference in how the motor behaves. I make sure the SA tables are also smoothed. The two go hand in hand.
Once I have a new VE calcs I look at areas that were not changed using TP graphing. I try to “smooth” areas in between sections that were changed. Smoothing makes a difference in how the motor behaves. I make sure the SA tables are also smoothed. The two go hand in hand.
Yep. I do that too. You can also pick-up typos like "8" instead of "80" for VE. Ask me how I know lol? Going down the highway and having the engine fall on its face ... ...
...The ECM makes the INT swing all the time. If you observe the INT on steady cruise, it just swings back and forth. That's normal...
When the prop gains are disabled, it forces the ECM to creates x-counts via the INT. Same if there isn't enough prop gain. One way or another, the ECM needs to see x-counts (in closed loop of course).
Too much prop gain and the INT will rapidly oscillate while chasing after the AFR. It can be a real fine line getting the prop gains correct. Which is why it is nice to have an open loop idle and an open loop decel option in the firmware.
One thing that is a worthwhile exercise, is to look at the cams that GM used. Both duration and lobe separation angle. Overlap is very low if at all. Note that I am posting more about the mid to newer LS cams. I was quite surprised at what I found (116° to 120° LSA was common).
RBob.
Last edited by RBob; 02-18-2024 at 03:20 PM.
Reason: fixed quoting
True! Forgot to mention I also disabled the Prop gain lol
Such a complicated system... antiquated IMO. Lately, I've been taking courses on tuning with newer systems. Ohhh my... the simplicity is beyond.
The newer system is even more complicated to get right. If you add headers have to mess with the proportional and integral stuff to get them right too. In addition the injector data needs to be spot on. I have my P59 run L31 based 383 dialed in spot on with OEM like air/fuel swings.
12-15-2023, 11:49 AM
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