Optimum Spark question

[chevota]

I read an interesting post in the GM section about Optimum being nothing more than an urgency table for main spark:
https://forum.hptuners.com/showthrea...rk-tables-how-

Basically the higher the value in Optimum, relative to Base, the greater the urgency it pushes the value in Base. If Base was 5 and Opt was 5 you have 0 urgency to drive to Base. If Base is 5 but Opt is 10, then you have a "5" level of urgency to drive to Base. I don't know what urgency is because if it's not the base of 5 at that moment, then wth is it?

I kinda doubt ours is the same, but that's why I'm asking. Originally I thought it was like it sounds, Optimum is the perfect timing if you had the octane to pull it off, and Base was minimum timing. Clearly that is not the case based on what I see, since my timing is often less than Base, which I can't explain at all. Not ping or Cat or tip-in retard, just retarded and I don't know why.

So what is the Optimum Spark? Eg; at 3k rpm and max load my oem Base is 5.25 and Optimum is 12.75. What does that really mean? What happens if either were changed?
Eg;
Base 10.5 and Opt 12.75
Base 5.25 and Opt 18.0
Or both raised to 10.5 & 18.0?

[chevota]

The way my timing is set now I get a little bit of retard here and there on one random cyl, sometimes two. So it's right on the edge and a perfect spot to experiment. So without touching anything else, I raised Optimum (MBT) spark to see what would happen, as seen in the attached pix. Yes there is a reason for the seemingly random choice of #'s, but I won't bore you with it. The main #'s of interest of course are full load above ~3k.
I was able to floor it eight times and zero retard! So whatever Optimum does, it doesn't add more timing, or urgency. An actual 1.5deg bump would've caused all kinds of chaos.
It doesn't seem to have retarded timing either so I can't explain the lack or retard. It is a bit cooler out at the moment, and/or maybe I have a better tank of gas, who knows. Timing is super hard to track with it moving around so fast, compounded by the delayed data, but in spots where it was kinda steady, under a good full load pull, it was the same as before. Not very scientific, but it's all I got. At the very least, I do know that advancing Optimum Spark did not advance timing.

So I'm back to assuming what I previously thought; Optimum is just that, ideal timing if octane was not an issue. So I guess it's really just a reference table? If so, then I guess it should never be advanced or retarded because those #'s are pretty much set in stone, but it'll never go there anyway so I guess it doesn't matter?
The note at the bottom of the window says; "used in torque calculations". I've learned not to trust those notes but I'm sure some are correct, and it adds to the reference theory. If so then I guess raising it just drops your torque calc, which I'd imagine indirectly bumps power? I'm maxed out, physically, so nothing happened for me. Maybe this indirect bump is why people do it? Perhaps people don't know why it worked, just that it helped?

All theories for the most part, but this is what my brain came up with. Still hoping someone in the know will chime in.

Opt bump.jpg

[Makeclick]

It's so shitty system so I think it's only used to finetune power/torque in the mercedes production line .

If you will add +3 to Optimum spark, you will lower your torque calculations, because real spark can't manage to go that far without the knock. If you combine your torque calculations (before and after change), you will see it getting lower.

There is way to make more power here... Maybe.. if you make it further and further, the car will try to compensate optimum torque vs stock torque

real stock spark logged 1,5 =400Nm 6000rpm < not real numbers, but example
Stock optimum spark 23 =400Nm 6000rpm < not real numbers, but example
optimum added +3(26) ~370Nm 6000rpm < not real numbers, but example
Your engine try to compensate 30Nm back to 400Nm

If you lower it to closer to the base spark, it will show higher torque values (when logged), but then the transmission starting to limit torque and you have wrong torque calculations. I don't know if this is accurate, but it feels like this way OR it can vary applications to applications.