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Thread: low BLM

  1. #106
    Fuel Injected! donf's Avatar
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    Quote Originally Posted by dhworkin View Post
    . Same things happening. Almost no throttle response.Attachment 14634 50% throttle and no power
    So just trying to figure out this from a computer screen. Dont worry about throttle response at first. Get the fuel tables dialed in with nice slow throttle movements. I am not sure how many hills Florida has, if you have any close, the hill and a little bit of brake dragging (don't over heat them) will help keep your speed in check and allow you to stay in the individual cells for a longer time. When you get it running decent just driving like a grandma then gradually build out your fuel tables with more load. I actually found that dragging my 5000lb trailer up a few long hills with low traffic was awesome for the nice slow rpm increases for looking at fuel tables under load. You could need more AE, or more timing, or you could have another problem, but so far I have not seen a nice slow log with lots of data over most of the fuel table that shows you have the base tables close yet. They may be, but I cant tell. If someone sees something I missed feel free to jump in.

  2. #107
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    mmm.xdl When it goes lean at a slow cruse there is a surge, and that happens with the timing at distributor set to 20 BTDC as well. It backfired thru the throttle body if I gave it to much throttle on this log

  3. #108
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  4. #109
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    OK that mmm xdl was a lot better, jumping around wise. I would work on getting your block learn numbers to run closer to 128. Lower is the computer pulling fuel, higher is the computer adding fuel. Some have mentioned the wide band does not always agree, but at least with my TBI they were very close. Watch the counts if the data seems out of wack. If its low on counts I would probably discard and hand edit that cell. Its worth a shot to see if you can make improvements in the drivability. I doubt this is all your problems but its a direction.

    mmm.jpg

  5. #110
    Fuel Injected! donf's Avatar
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    I was looking at the VV.xdl. You are doing a lot better not jumping around. See how all the BLM numbers are slowly counting down? It is adjusting. Spending enough time in each cell to get a good average is important. Put that data into the spread sheet and see what it starts to look like. I think as you work on the table the drivability will improve. When you reburn the chip, disconnect the battery each time to start fresh.
    Last edited by donf; 3 Weeks Ago at 08:00 PM.

  6. #111
    Fuel Injected! donf's Avatar
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    What happened between logs VV.Xdl and ass.xdl? are those right after each other with no changes? ass.xdl looks a lot worse blm wise. It must be really late in FL. I will catch up with you tomorrow. We will get it figured out.
    Last edited by donf; 3 Weeks Ago at 08:11 PM.

  7. #112
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    Going over the VV and ASS files. Maybe they are not as far off as I thought at first. In the early file, there are more populated cells closer to 128 but the sample count on a lot of them is low.

    Also, the data recorder is not that advanced. I did not know this before this morning. if you run two log files back to back its just going to add them together. It will not clear data unless between files unless you hit the clear button on all screens or close the program and start fresh. So if you are playing pre recorded data, skipping between files, fast forwarding, etc. Its pretty easy to get data log screen data that is complete jumble mess of all the files and not what it would have been if the screen had just been left open on a test drive and then stopped. When messing with it, there are definitely some crude parts to the freeware. We get what we pay for ha ha.

    What I would do is open TunerPro new each time I did a test drive. I would let it warm up to 180 or so then start the log and then at the end of the drive copy and paste all end data to a blank spread sheet as the end average numbers are what I was most interested in anyway. Then I would look at the counts if there were low count cells or cells set in transition, or some hangars that seemed way out of place I would remove those or edit them by hand. Once that is done I would put them into the other spreadsheet for adjusting the fuel table values. Its definitely not an once and done process. You can get a good base though and sneak up on better as time allows.

    I was also looking at your wideband data, the min and max numbers for each cell are pretty far apart. Also the narrow band o2, sensor, how old is it? Just curious as after looking at your BLM # and the wide band data there may be be some discrepancy. Others have mentioned this before. With mine I started with a fairly new sensor but with about 30k on it, then wondered the same thing and swapped to a new AC delco. There was some differences in the numbers I got after the swap, but not a huge amount. If the sensor was original, I would have definitely replaced it with a good quality senor before starting the process. I was just wondering if an old narrow band with a lot of miles feeding info into the computer may be part of the problem? Just wondering, it may be nothing.

    After the tables are roughed out a little closer you can work on AE and PE. Some here recommend disabling those for the first part, but for myself just being careful with crazy throttle movements and starting low on the table and gradually working into the higher load areas seemed to work fine. My set up was more conservative though, it actually took a second or two to transfer in to PE at WOT. Not crazy long, but I got very good mileage even with the 4.10 gears. Your choice on if you need to lock it out or not for the rough out of the tables.
    Last edited by donf; 3 Weeks Ago at 10:00 AM.

  8. #113
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    Hey donf, yes I was back to back logging on those files. I have been having and was experiencing the worst of my problems so far and started driving in a way as to get the timing issue to show its face. It's not a glitch, it's the knock sensor. The sensor does not seem to be bad as far as testing and never set a code, but I thing it may be over sensitive so I ordered a new acdelco. I figured this out last night so I removed the knock sensor, Teflon taped the threads, reinstalled it hand tight, and so far today it's running like it should. I hope this is the fix and that I can have fun with tuning instead of fighting with it. I'll log data and post it tonight. Thanks again for the info, your last post cleared up a couple problems I was having.

  9. #114
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    That doesn’t sound like the sensor. The sensor is likely performing exactly as designed. In addition, a knock sensor code is only set if the internal resistor fails (for 84-95 vehicles) and almost always has nothing to do with the operation of the sensor element itself. If adding Teflon tape to artificially dampen the sensor’s ability to do its job fixed the issue, it means the knock module in the PCM is incorrect for your application. This is what takes the raw reading from the sensor and interprets what is knock and what is normal noise. By defeating the sensor you are just masking the issue.

    Personally I would want to go the route of finding a proper knock module, but scalpers on eBay are selling LT4 modules for $300+ and other modules have been largely untested as to what frequency ranges they are effective at in terms of knock detection. So short of creating your own module based on dyno-tested research of the sensor outputs, that’s not an option it would seem.

    Personally, if you’re going to defeat the sensor anyway, I would just go into the computer and disable both the knock sensor codes as well as set maximum knock retard to 0, disabling the ESC system. I mean, you’ve already crippled it, so why not?

    Sincerely, someone whose loud exhaust causes his PCM to retard timing too.

  10. #115
    Fuel Injected! donf's Avatar
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    Unless your are jumping on it at WOT already getting way out of the areas you logged last that we can not see, your last two log files showed very little knock retard. Even with data set to running maximum. Lean areas can cause knock easier and I still have not seen a good log that's close to 128 at lower loads, let alone anything working higher. I would hate to disable knock detection on a truck either in the computer or with teflon tape. Just like the a few others here saying they could not run in closed loop and they had to disable it. They might as well bolt on a carb, as they are loosing a lot of the benefits of FI. I think with proper tuning steps there may be another way for both of those extreme actions. Its up to you though.

  11. #116
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    The previous logs that I posted was done when the truck was running the worst it ever has, it would barely go 50mph and was bucking. This log was done with one wrap of tape on the knock sensor. It is still counting knocks.oo.xdl I just removed the tape and will post a log later today. I'm thinking that it could have been a bad connection, just glad it's safe to drive now. I'm in this to deep, I don't plan on taking any shortcuts.

  12. #117
    Fuel Injected! donf's Avatar
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    Knock counts don't really mean anything by themselves unless they are increasing drastically as driven. All gm vehicles have them even stock, my van would set 80 or so just starting up. I remember looking at them on the tech2 at the dealership when new, and thinking it was bad at first, but after a while it was like eh, they all do that. It is the knock retard that needs looked at. I am not sure how good turner pro RT is accuracy wise, but I think for now it does seem to show knock retard when its present. From the last post and looking at the last log file. I did not see any real knock retard to suggest that was your problem. BLM values of 105 is a lot lower than the ideal of 128. So you have some rich areas that the computer is pulling fuel from.

  13. #118
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    Starting to understand, no more BLM values of 105. zz.xdl I made the changes using the BLM spreadsheet, hand edit, highlight entire table and smoothed at .7 I tried to figure out the wideband o2 spreadsheet but never found a tutorial. I need help with that and a lot of other things as well. Truck is running better and I can close the garage door as soon as I pull in. Very thankful.

  14. #119
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    Awesome news! Yes, much better BLM numbers! I always used the wideband log as a verification for the PE settings under WOT as they are based a lot on the VE %, although there is the AFR mixture table that works with that. Also to verify the stoich mixtures in the rest of the table. My blm readings did match up to the wideband, almost exactly in all areas not under PE. Some say they are not that lucky. See how your average numbers are gradually counting down in the last file? You can probably creep up on the VE table with a little fine tune, by using the part of the spread sheet that averages the difference with a few more long test drives. I would do at least one more pass doing just what you did to get these results. You did very good! One thing I did NOT do in the final stages is use the smooth function very aggressively. There were cell values that did want to be a little higher or lower than their neighbors, and repeatedly smoothing them, just resulted in me chasing the same small changes only to knock them out with the smoothing function. So once the table had its basic shape, I relied mostly on the averaged numbers and hand editing to end up where I wanted to be. You can never get it perfect, but you will learn where to stop.

    Once your ready to transition into the medium and heavy load areas... If I did not have my dyno, I would borrow the biggest, heaviest trailer (within reason) I could find from someone I knew as things happen much slower with the added weight and are easier to see on the logs without exceeding the speed limits or driving illegally. This is where the wideband really helps make the picture complete to get the tune dialed in good. A ride along person can watch in real time and give feed back on what the wide band is doing. On AE you have to pay attention to how the vehicle responds, not just the wide band numbers as making it rich enough to go directly to your wide open fuel mixture with any movement of the throttle will usually be way too rich for decent fuel economy and horrible for emissions. What I looked for is a slight lean condition, not horrible, but then quickly transitioning to your PE mixture if you stayed in it. I ended up taking a little AE out in my final changes, as it did not affect driveability and my mileage increased noticeably.
    Last edited by donf; 2 Weeks Ago at 06:17 PM.

  15. #120
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    You were right about a problem with the O2 sensor readings. After some good log's I noticed the BLM's dropping as you said and noticed that when the fans turned on they dropped to 105. So I logged with the AC on (which turns the fans on) and found a problem. I used the pink wire that was left from the EGR delete to power the key on power to the relay for the fans. After disconnecting from the pink wire (that also powers the O2) it stopped and made things work a lot better. Thanks for bringing that to my attention.

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