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Thread: How do you build a Spark Table from scratch?

  1. #1
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    Question How do you build a Spark Table from scratch?

    I've got a 383 SBC with an LS1B (411). There are a LOT of modifications, including TPI, 11:1 compression, headers, port matching on the intake and a high-lift cam (Lunati 20080720 w/ 1:1.6 rockers). The transmission is a 4L80E, with a 3.08:1 rear and 26.9" tall tires, all in a 3800 Lb. car.

    Someone posted a tune for a '91 'vette with TPI (from Yellow05C6 here), but that has 16.9 degrees of initial timing, and I think that's too much for this engine/car.

    I know that I have to create a spark table for this, as the LS1 table is unlikely to work properly. How do people do this from scratch?

    I'm thinking that I can use six values from distributor tuning (Initial advance, Total mechanical advance, Mechanical advance start, Mechanical advance done, Total vacuum advance and Vacuum advance in by), and use the VE table to get an acceptable starting point. Does this make sense?

    EDIT:

    I finished the tool, cleaned it up and created some documentation. Everything is attached to this post. The ZIP file contains some sample data derived from the "Stock '91 Vette_0000.ctz" file referenced above.
    Attached Files Attached Files
    Last edited by WhisperPC; April 11th, 2017 at 04:00 AM. Reason: found source of a tune

  2. #2
    Joe (Moderator) joecar's Avatar
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    Without a dyno you have to borrow pieces just like you said...

    and then you have to pay attention to see if you can detect knock (use knock phones).

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    I finished the code (it's in Python - big, ugly, un-optimized and poorly commented), and it generates nice tables (they look just like a curve from a distributor should). The problem is that I can't use Windows copy/paste to transfer the table from Notepad (or other editor) to the tables in Tune. I've tried spaces, commas and tabs as the field separator, and none of them copy/paste properly. This is a LOT of information, and typing it in is a pain.

    What do I need to add to allow copy/paste to work?

    Once this works, I'll look into cleaning the tool up and moving it to the next step.

  4. #4
    Joe (Moderator) joecar's Avatar
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    Can you write it as a CSV file...?

    ~Moderator~

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    Quote Originally Posted by joecar View Post
    Can you write it as a CSV file...?
    I adjusted the program to use a comma delimiter, and saved the output to a .CSV file. I then brought the .CSV file up in Excel and was able to copy/paste from the spreadsheet into the Tune tables.

    While I don't like having to use Excel as an intermediary, I can live with it. I'll start cleaning the code up.

    A sample spark table graph is attached.

    ----------------------------

    The spark curve is generated from the VE table and six values from distributor tuning (Initial advance, Total mechanical advance, Mechanical advance start, Mechanical advance done, Total vacuum advance and Vacuum advance in by). Is there anything else that I could add to make this more flexible?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by WhisperPC; March 15th, 2017 at 07:24 PM.

  6. #6
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    Quote Originally Posted by WhisperPC View Post
    The spark curve is generated from the VE table and six values from distributor tuning (Initial advance, Total mechanical advance, Mechanical advance start, Mechanical advance done, Total vacuum advance and Vacuum advance in by). Is there anything else that I could add to make this more flexible?
    I added the ability to have a floor and a ceiling for the advance, a boost retard and the ability to have multiples of each. This allows a rather complex spark advance curve to be created.

    Next, I'll add specification of the VE table as a file, specification of the spark files, and the output files, all in the parameter file. This will allow a single parameter file to generate multiple spark tables (high-octane, low-octane, in gear and P/N) for the same engine in one pass.

    If anyone is interested in additional features, please ask.

  7. #7
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by WhisperPC View Post
    I adjusted the program to use a comma delimiter, and saved the output to a .CSV file. I then brought the .CSV file up in Excel and was able to copy/paste from the spreadsheet into the Tune tables.

    While I don't like having to use Excel as an intermediary, I can live with it. I'll start cleaning the code up.

    A sample spark table graph is attached.

    ----------------------------

    The spark curve is generated from the VE table and six values from distributor tuning (Initial advance, Total mechanical advance, Mechanical advance start, Mechanical advance done, Total vacuum advance and Vacuum advance in by). Is there anything else that I could add to make this more flexible?
    Looks good to me... have you run it...?

  8. #8
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    Looks interesting, at the end of the day you're going to have to log it and add/remove spark as to what the engine wants. This is the benefit of using the PCM vs a dizzy, but it should get you in the ballpark as a startup tune.
    ~Erik~
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    Lifetime Member Chevy366's Avatar
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    Quote Originally Posted by WhisperPC View Post
    A sample spark table graph is attached.

    ----------------------------

    The spark curve is generated from the VE table and six values from distributor tuning (Initial advance, Total mechanical advance, Mechanical advance start, Mechanical advance done, Total vacuum advance and Vacuum advance in by). Is there anything else that I could add to make this more flexible?
    Are electronic pulses as mechanical as that? Timing in these tunes is linked to several other parameters in the tune so timing affects a myriad of other parameters when altered.
    I watched a friend with HPTuners put 22*s in all cells of the main timing table (Ho,Lo), fired the truck up and it ran, no knock and had good acceleration. Was amazed. I was like, it shouldn't be running so well, but it did. He actually tried to rid the tune of all spark modifiers.
    2005 1500 HD , Custom OS3 SD tune .
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    Dinosaurs and Plants gave their lives so that we may drive , long live fossil fuel .

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    Quote Originally Posted by joecar View Post
    Looks good to me... have you run it...?
    It ran better with the above spark table then it did with the stock LS1 spark table.

    I'll be adjusting the VE table next and calibrating the MAF (https://forum.efilive.com/showthread.php?15236). After that, I'll come back to the spark curves.

    Quote Originally Posted by ScarabEpic22 View Post
    at the end of the day you're going to have to log it and add/remove spark as to what the engine wants. This is the benefit of using the PCM vs a dizzy, but it should get you in the ballpark as a startup tune.
    The purpose of the tool is to get close enough to start tuning. With the recent (ongoing) software modifications, minor adjustments become easier, so it should be possible to get closer.

    Quote Originally Posted by Chevy366 View Post
    Are electronic pulses as mechanical as that?
    Most spark tables are nowhere near that geometric. The table my program creates isn't optimized. It's just close enough to get the vehicle running fairly well. The closest shop with a dyno that can optimize the spark tables is about 40 miles away, most of it on Freeways. I'd like to get it adjusted well enough to get there without a trailer or tow truck.

    Quote Originally Posted by Chevy366 View Post
    I watched a friend with HPTuners put 22*s in all cells of the main timing table
    That makes no sense to me. There's a reason for distributors being complex, and spark tables are even more so. The spark needs time to get the fuel vapors burning properly, and that time varies with the charge density (engine vacuum and compression ratio) and several other parameters.
    Last edited by WhisperPC; March 15th, 2017 at 04:05 AM.

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