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Thread: Adjusting the VE table, I'm not sure I understand it, but I tried it.

  1. #1
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    Adjusting the VE table, I'm not sure I understand it, but I tried it.

    So I finally decided to try and adjust the VE table since the numbers looked to be on the rich side.

    I've read what seemed like several different ways of doing this and I'm not sure I understand it.

    In any case, I decided to try it and see what happens.

    The first two pictures are the blm and int with no changes made to the VE table.




    The next two, I adjusted the VE table by using the formula where: BLM/INT*(VE1 value + VE adder)-VE ADDER. I then left the values in the VE adder table.

    These were done the next day where I drove the freeway home so I could get into the higher rpm's to see where those numbers were sitting.




    The next two are after an adjustment made to the higher rpm's and a long drive on the freeway.




    I'm not real sure of how much closer I could get with them, but I am hoping that I've done the adjustments properly. It sure seems to run pretty nicely.

    The freeway I traveled speed limit is 75 where 90 is not much of an issue if you aren't tailgating. The speedo max on my truck is 85, but I had her up to 90 by the gps reading and it felt like she had more to give. I just wasn't sure I wanted to take it further because who in the world knows when the last time that thing was past 80mph.

    Also, if you look at the logs, the knock counts, I don't believe are correct. One of my logs showed a total knock count of 27, and I know that was bogus because the program started with 27 before I even started the engine.

    The attached log is from Friday afternoon. No other adjustments were made prior to this log other than what was described above.

    Anyways,

    Thanks for any advice, criticism, and or comments.
    Attached Files Attached Files

  2. #2
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    judging from the BLM history table youre pretty damn close, maybe keep the blm counts around 125 ish.
    '86 Grand National

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    yeah, you definitely took a step in the right direction based on what the BLMs look like compared to the stock table.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  4. #4
    Fuel Injected! 1BadAction's Avatar
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    Quote Originally Posted by damanx View Post
    . I just wasn't sure I wanted to take it further because who in the world knows when the last time that thing was past 80mph.
    I feel your pain on this one.

    BLMs look close to me, I wish I could have gotten mine that close before I left off with it.
    2010 Porsche Cayenne GTS - DD
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    EFI GearHead ! EagleMark's Avatar
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    Even if you got your BLM closer today? They change with weather tomorrow. Your done there. Nice work!

    I adjusted the VE table by using the formula where: BLM/INT*(VE1 value + VE adder)-VE ADDER. I then left the values in the VE adder table.
    I use a spreadsheet.

    Next thing to look at is your VE table in Graph mode. As you have found out you can't hit all cells. If you are in one cell it does not use it alone, it is interpolated with the four surrounding cells to come up with the number. So if all you did was adjust the cells you kept hitting, then look at table in graph, you will have some peaks and valleys.
    http://www.gearhead-efi.com/Fuel-Inj...4-7747-ve1-ve2

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  6. #6
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    Quote Originally Posted by EagleMark View Post
    Even if you got your BLM closer today? They change with weather tomorrow. Your done there. Nice work!
    Thanks!

    Referring to the weather, I noticed a huge difference in how the engine ran with the carburetor, and it drove me NUTS!

    The temp dropped off a little last night and the tables showed to be on the leaner side, but by 3 or less points here and there.

    On the drive home, the numbers were in, so the change in weather and slight table differences make sense.

    So, I wonder, if using the 512 chip with a bin for below 80 and one for above 80? Is it possible?

  7. #7
    EFI GearHead ! EagleMark's Avatar
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    Quote Originally Posted by damanx View Post
    So, I wonder, if using the 512 chip with a bin for below 80 and one for above 80? Is it possible?
    Or you could not worry about BLM numbers and let the EFI do it's magic. Your so close to perfect it has loads of room either way to adjust to perfect for you. Think of it as automatic adjustable jets in a carb...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
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    ^ X2.

    as long as your BLMs are consistent across the table, then you'll be perfectly fine. there are a lot of variables that will effect the fueling that the PCM just can't account for(humidity, for example), thats where the O2 sensor will come in and adjust. if you see BLMs of 124 across the entire table, then once the BLM drops to that after entering closed loop, it will be correct for all cells.
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  9. #9
    Super Moderator dave w's Avatar
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    Quote Originally Posted by EagleMark View Post
    Or you could not worry about BLM numbers and let the EFI do it's magic. Your so close to perfect it has loads of room either way to adjust to perfect for you. Think of it as automatic adjustable jets in a carb...
    I agree with Mark! With BLM's that close, the Block Learn can do what it is designed to do!

    dave w

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    I agree, I will leave those alone and run it like that for a while and see how she does, which is pretty impressive for this old beast, and not so much the engine, but everything else! LOL

    This is probably a dumb question, but when running a log, does the playback speed matter?
    Last edited by damanx; 04-29-2013 at 04:39 PM.

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    This is an update with some questions.

    I've been running the same table as posted above for a few days now, and I've noticed a couple things that have me curious.

    Obviously, and please correct me if I am wrong, but it appears that the ecm practically relearns everything to an extent at every start up.

    I'm seeing that, with my typical driving pattern with this truck that my numbers are slightly off than what you see in the tables above. That day, I did a lot more driving than what I normally do.

    My typical drive to and from work is about 20 minutes with speeds up to an average of 60.

    So, I can understand seeing cells that would be off by a few points per se in comparison to the above table if there is not enough time spent in them for the ecm to work it's magic.

    Which brings up this question of if I am seeing numbers that indicate a more lean, but not terribly lean, condition with my more common driving habits, would I want to adjust the table slightly so that the condition is slightly richer than leaner? I ask this because would not a slightly richer condition be better for engine life?

    Edit to add: What I am seeing is that the cells that are being used seem to be starting with numbers between 128 up to 134 until they are brought down.

    Second, I'm not sure my math skills are all that great and if I wanted to adjust the numbers again, and using the formulas, how much of a difference should I see?

    Third, I am assuming that I should be able to tweak the current ve table, or, should it be with the original?

    Edit to add that if it helps, I'm not sure how the numbers relate proportionally to the stoich mixture number, i.e. BLM 116 is about equal to 12:1 where and 141 is equal to 16:1, or is it more like 116 is equal to 14:1 and 141 is equal to 15:1. Hope this makes sense.

    Thanks!
    Last edited by damanx; 05-01-2013 at 05:15 PM.

  12. #12
    Super Moderator dave w's Avatar
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    I don't have any BLM vs. AFR data from a 1227747 ECM. The data I have is from a 16197427 PCM located in this thread: http://www.gearhead-efi.com/Fuel-Inj...ing-AFR-vs-BLM As a guess, I'm thinking the 1227747 ECM would think BLM 116 = AFR 13.8:1 and BLM 141 = AFR 15.0:1. With the 16197427 PCM, I disabled BLM update to get consistent AFR tuning (VE Tables ~ yes the 16197427 has two VE tables off idle / near idle).

    dave w

  13. #13
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    if the blm is slightly higher/lower than 128 doesnt necessarily mean its running rich/lean. unless of course its pegged at its limit in either direction. as long as the blms are within its limits, the ECM will calculate them to keep engine running at the commanded AFR.
    '86 Grand National

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    Thanks 34blazer.

    That is what I was curious about as I think I am being too anal about the numbers being spot on. EagleMark mentioned that they would change based on environmental conditions.

    I drove it 70 miles round trip this afternoon and the numbers were different than what they have been, all showing corrections for a richer condition, but this being done in a different part of the day, I can understand the differences, but they were all within the ranges of the blm/int.

    Will post screenshots of the tables in a bit.
    Last edited by damanx; 05-02-2013 at 05:50 PM.

  15. #15
    EFI GearHead ! EagleMark's Avatar
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    Quote Originally Posted by damanx View Post
    That is what I was curious about as I think I am being too anal about the numbers being spot on.
    Yup!

    But you bring up good questions, none of which will change that fact that your well within range and the system is adjusting to Stoich because of O2 sensor feedback.

    If it were OBDII it would be easier to see as it deals in:
    INT = Short Term Fuel Trim based on percent + or -
    BLM = Long Term Fuel Trim based on percent + or -

    So OBDI deals with 256 bit and 128 is middle, no adjustment, 0%. 128 /100 = 1.28% so 116 BLM = 10.24% adjustment. You could do some math and say if BLM were 116 then afr would be? But the narrow band O2 sensor is only very accurate at half way point of voltage which is .451, either side of that is a crap shoot for AFR.

    BLM or INT has nothing to do with AFR, it's a correction of fueling to achieve Stoich

    Your also dealing with a system that has an ALDL data response every 1.2 seconds so how much data you see is not indicative of how much adjusting is going on.

    Math for BLM to adjust VE is BLM/128 = X * VE = new VE. Or the easy way with an option of average is to use the spreadsheet in this thread:
    http://www.gearhead-efi.com/Fuel-Inj...Information-42

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
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