Bringing TBI and Multi Port Fuel Injection to a New Level.     EFI Conversions and Tuning! Seattle to Portland! E-mail Tuning Consultant!
Results 1 to 13 of 13

Thread: What should I do about my main spark table?

  1. #1
    Fuel Injected!
    Join Date
    Mar 2019
    Location
    Camarillo, CA
    Age
    43
    Posts
    68

    What should I do about my main spark table?

    79 Jeep, AMC 401, 6197427, 454 throttle body, $OE, Tunerpro RT, Iron heads, 91 octane fuel, ~9.5:1 compression, forged pistons, Mechanical advance is welded, vacuum advance removed, .

    I have my computer controlling my timing and it seems to be working correctly. I have installed a 454 knock sensor into the side of my block and wired it up. I do not get a check engine light for my KS unless I unhook it so I assume it is working correctly. My Jeep runs pretty well but is a bit gutless toward the top end.

    Took it out for a run today, and logged my data. I had no knock retard ANYWHERE in my history tables. Literally, it was all 0's. I also did not hear any knocking/pinging while I was driving it. This made me assume I have no knock and intended to add 2 to 4 degrees to my table when I got home. But as I looked at my average timing table I see there were times when I was at almost 44 degrees! (here's my history table from TunerPro)
    Spark history.jpg
    If I compare the history table to the main spark table, the truck seems to be doing what it is supposed to: (here is my main spark table from my BIN)
    main spart table.jpg

    So I'm stuck. Do I go after my knock sensor assuming it is not working? Do I just assume, with 91 octane it will not knock, and take some timing out of it and see how it performs? Or do I keep adding spark until I get problems? Or am I missing something all together?

  2. #2
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    4,581
    There is the option of temporarily disabling the Knock Sensor to compare the history tables, with knock sensor and without knock sensor.

    Possibly tap on the block, near the knock sensor, with a small hammer (vehicle in park at or near idle RPM's) and see if the history table records any knock retard.

    It would be a good plan to look at knock counts in the exported data log, aka .csv Excel spreadsheet.

    dave w

  3. #3
    Fuel Injected!
    Join Date
    Mar 2019
    Location
    Camarillo, CA
    Age
    43
    Posts
    68
    Good idea! I’ll try that out this week and post up my results.

  4. #4
    Fuel Injected!
    Join Date
    Mar 2019
    Location
    Camarillo, CA
    Age
    43
    Posts
    68
    OK, I rapped on it with a hammer and it looks like I got a little knock retard.

  5. #5
    Fuel Injected!
    Join Date
    Mar 2019
    Location
    Camarillo, CA
    Age
    43
    Posts
    68
    OK, I rapped on it with a hammer and it looks like I got a little knock retard. Not nearly as much as I would expect though.

  6. #6
    Fuel Injected!
    Join Date
    Nov 2017
    Age
    53
    Posts
    284
    There are at least 5 knock sensors for that computer. V-6, 305 manual trans, 305 auto trans, 350/454 manual trans and 350/454 auto trans. Being a different block completely you will have to see which one is more accurate in your block. Then there is also the knock sensor circuitry in your memcal
    Last edited by In-Tech; 05-22-2020 at 11:23 PM.
    -Carl

  7. #7
    Carb and Points!
    Join Date
    Jun 2020
    Age
    56
    Posts
    4
    Only a newbie, but I know the frequency of the knock 'sound' is related to bore size, and computer input is electronically filtered to listen to that particular frequency for knock detection.
    I'll leave it up to you to determine if that's of relevance here.

  8. #8
    Fuel Injected!
    Join Date
    Mar 2019
    Location
    Camarillo, CA
    Age
    43
    Posts
    68
    Rather than start a new thread, I will hit this one. First my original issues WAS:
    When I first started my truck tuning adventures, I did not have a knock sensor so I disabled all the timing retard capability by setting the "minimum temperature for knock retard" to 151C in my BIN, and promptly forgot about it. I also had retarded a bunch of the timing table because it looked like too much timing. Luckily I keep a log with every change I make to my BINs so during a look back over my notes, I saw it, put it back to 35C and added 4 degress of timing to the whole table. Now that I turned it back on, I not only have knock counts, I have timing being retarded the way it is supposed to!!! WOOO HOOO!!!

    MY QUESTION NOW, THOUGH:
    I have done a tuning run with my timing tables and have data on my knock retard. Do I just take that Knock retard number (running avergage), subtract it from the value in the timing tables, install new table in my truck, rinse, and repeat? Am I looking for 0's or just less than say .5? Is it really that easy to tune timing? I feel like I am over simplifying it...

  9. #9
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    4,581
    Usually spark changes of 1 or 2 degrees will change the knock retard averages. It can be challenging to reduce knock retard, because increasing or decreasing Spark Advance will affect knock retard averages. Sometimes adding Spark Advance will eliminate knock retard averages, which seems counter-intuitive.

    dave w

  10. #10
    Fuel Injected!
    Join Date
    Mar 2019
    Location
    Camarillo, CA
    Age
    43
    Posts
    68
    Copy that. When I was trying to see why my knock sensor was not reading, I added a bunch of timing to my tables. I started with 454 tables and having an over square engine, I need more then 454. So I think I am in the ball park.

  11. #11
    Carb and Points!
    Join Date
    Jun 2020
    Age
    56
    Posts
    4
    Quote Originally Posted by dave w View Post
    Usually spark changes of 1 or 2 degrees will change the knock retard averages. It can be challenging to reduce knock retard, because increasing or decreasing Spark Advance will affect knock retard averages. Sometimes adding Spark Advance will eliminate knock retard averages, which seems counter-intuitive.

    dave w
    Pardon for butting in, but I've just started playing with tuning LS1, and spark seems harder to tune than fuel, at the moment.
    Dave W, would it be fair to say that having the tune take timing out due to knock detect costs you more performance than not having quite enough advance and no knock in the first place?
    I base that on observation from logging. I have a 'test dyno' bit of road that I log acceleration from 2 to 5 000 rpm in 3rd gear on, and use time scale to measure performance, quicker the better.
    Obviously no correction for airtemp, barometric etc, but pretty indicative, and 'real world' conditions.
    I am assuming more advance is more power, but upon reflection of that, maybe that's not true.
    And am I placing too much faith in my test method, as well?
    Again, sorry for jumping in, not wanting to hijack your post rang-a-stang.
    Last edited by Mr Weston; 2 Days Ago at 09:59 AM.

  12. #12
    Fuel Injected!
    Join Date
    Mar 2019
    Location
    Camarillo, CA
    Age
    43
    Posts
    68
    You're good Mr Weston (not hi-jacking at all). This is all information I am hoping to discuss.

    My understanding from reading other threads on timing is most folks will continue to add timing until they get high knock counts and retard, then back the cell(s) down just a tad. There is a finite point where there is too much timing. We want the max timing possible but as soon as we hit knock, we are losing efficiency (obviously there is knock from other conditions besides timing but for this conversation we are speaking purely of timing).

  13. #13
    Carb and Points!
    Join Date
    Jun 2020
    Age
    56
    Posts
    4
    Thanks for the info, rang-a-stang.
    Whilst having a think about it, another thing I remembered was that you're most likely to get knock at max torque, and I've seen that in my logging.
    Seems I can add more down low, and no knock,but not so much around 4000 rpm in my LS1.

Similar Threads

  1. Replies: 2
    Last Post: 08-10-2018, 06:50 AM
  2. Spark Table Suggestions
    By bgott in forum GM EFI Systems
    Replies: 3
    Last Post: 03-14-2018, 10:47 PM
  3. 95 4.3 TBI spark table info
    By ironwill11 in forum GM EFI Systems
    Replies: 13
    Last Post: 08-25-2016, 08:39 PM
  4. Main Spark Bias advice needed
    By Kitch in forum GM EFI Systems
    Replies: 2
    Last Post: 07-26-2016, 01:55 PM
  5. Replies: 0
    Last Post: 06-14-2016, 07:28 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •