How do you build a Spark Table from scratch?

[WhisperPC]

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 (https://forum.efilive.com/showthread.php?27032-Looking-for-TPI(L98)-to-LS1B-stock-conversion-TUNE&p=234361&viewfull=1#post234361)), 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.

[joecar]

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).

[WhisperPC]

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.

[joecar]

Can you write it as a CSV file...?

~Moderator~

[WhisperPC]

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.

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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?

[WhisperPC]

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.

[joecar]

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...?

[ScarabEpic22]

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.

[Chevy366]

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.

[WhisperPC]

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.


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.


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.


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.

[WhisperPC]

I finished the tool and linked it to the OP. If anyone's interested, please feel free to have fun.

Please inform me of any bugs found in the code or the documentation.

[ScarabEpic22]

Thanks for posting back, I've downloaded and will take a look at it in the next few days!

[joecar]

WhisperPC, thanks, good job :cheers:

~ by phone ~

[Chevy366]

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.

Thanks for the work done.
I agree, but he is or was a small engine mechanic and made the observation that small engines didn't have a spark curve. Although load is different they still ran fine. I asked him to use a Dyno spark table and see the difference, believe it or not the straight across the board table ran better and had better acceleration than that of the Dyno tuned one. Don't ask me why, it shouldn't work, but it did. Crazy! Like I said he removed all spark modifiers that he could find.

[WhisperPC]

will take a look at it in the next few days!
How did it work for you?

[joecar]

Follow the instructions in the pdf using the sample files provided (in the .zip)(you can edit the sample files to put your own timing numbers in there), the program generates .csv files that you paste into your tune as explained by the pdf, it's very easy to do.

( For Linux: python is already installed. For Windows, you may have to install python, see here: https://www.python.org/downloads/windows/ )