A few spark questions perhaps?

[Bruce Melton]

So, if you are tuning a manual trans C5 or probably most any LS1/6 and you want to add spark at idle you add it in B5932 (Base Spark in Gear) and if you want to have more (or less) total spark in the upper ranges you add to B5913 (High Octane table), or should you do it all in 5913?
I think I have done both but wonder what is the perscribed method and wonder if I am missing something?
Thanks as always,
Bruce

[SSpdDmon]

It depends on the base spark threshold settings. You should be in the BSIG table as long as your under the thresholds (TP% and mph). Stock I think they're set 1.19% and 256mph, which basically eliminates the MPH threshold and makes it solely based on TP%. They're found in the Engine>Spark>General>Parameters directory.

If you reduce the spark in the high octane table, remember to do the same in the low octane table unless you want to keep the knock learn factor from changing your timing, in which case the high table should equal the low.

Base spark tables (in gear and P/N) should be identicle.

[TAQuickness]

Another thing about the base spark and octane tables, you want to be mindful of the setting, particularly in the idle area. I found for smooth transitions out of idle I needed to match my base and octane tables.

[Bruce Melton]

Another thing about the base spark and octane tables, you want to be mindful of the setting, particularly in the idle area. I found for smooth transitions out of idle I needed to match my base and octane tables.

SSD and TAQ,
I think I get it and since the base spark maxes out @ 4,800 rpm the upper spark tables are managed by the octane table?
For my own use I have copied the high octane table to the low since I only run one grade.
Good point on matching all the lower rpm tables for transitions.
Thanks

[TAQuickness]

I found the matching was only important in the idle range for smooth transitions. Other than idle, I don't spend much time in the base table (not that I'm aware of anyway).

[Bruce Melton]

So it is appropriate to "fill in" the octane table <~2,400 rpm with your desired idle timing, say 24* to match the base table?

[TAQuickness]

I'm not a spark guru by any means, so I would not feel comfortable saying it's appropriate. Would be better to say it's not in-appropriate. I'll send you a copy of one of my tunes so you can see what I did.

[SSpdDmon]

I'd say as long as the jump isn't too big, you would be fine to have different numbers between the high octane and base spark in gear in the idle regions. In an M6 car, the base tables are only used for off-throttle scenarios. That essentially means idle and decel, right?

When setting idle timing, I know the car will survive in the 22~28* range with ease. I also know with my cam (and based on experience with tuning A4 cars), you're going to need at least 28~29* when accelerating from a stop. So, I set my idle spark at 25* for the 400, 800, and 1200 cells under .28 grams/cyl, which would keep the jump to the high octane table <4*.

If you notice in the pic below, my base spark has a ceiling of 35*. In other words, that's the most timing commanded anywhere in the table. Following the format of an '00 f-body base spark table, I then set the 1600 cells 4 degrees higher at 29*, 2000 cells 4 degrees higher at 33* and all cells 2400 and up to 35*. To bring in the newer concepts found in the '01 f-body base spark tables, I copied any cells to >.28 grams/cyl that were LESS than the timing value to the left. For example, in the 3200rpm row, my timing in the high octane table didn't drop below 35* until airflow was at .40 grams/cyl and greater. So, I copied those cells only. The result is something that looks like this:



To answer your question about 4800+ RPMs, the timing is still commanded from the base spark when off the throttle. It just uses the last line in the table (in this case the 4800rpm row) until DFCO kicks in and drops timing down to ~4*.

[dfe1]

With the cam that you list, I think it's very important to have spark in gear very close to the value in the high/low octane fuel tables. I always copy the high octane spark table to the low octane table unless I'm tuning a car for an idiot driver. One of the things to keep in mind is that the LS1/LS2-based systems have quite a few spark modifiers, and with the idle instability that's inherent with a long duration cam, some of these come into play when you don't want them to, unless they're tuned properly. In my C5 (01 6-speed, 232/236 cam) spark at idle moved around a lot until I refined the idle overspeed/underspeed spark settings. The effect of the low octane spark table (if values don't match those in the high octane table) can have a similar effect.

Some people think the low octane table has to be maintained with lower values than the high octane table, but as far as I can see, the low octane table IS what its name implies. It's included because a surprising number of people will buy a high performance car and then fill the tank with low octane fuel. I had a conversation with the lead engineer for the most recent supercharged 3.8-liter engine (Grand Prix) and one of their design goals was to develop the engine so it produced 250+/- horsepower on 89-octane fuel-- because that's what a lot of customers were requesting. Why anyone would pay a premium for a supercharged engine and be too cheap to use premium fuel is beyond me, but that's another topic altogether.

[bink]

Might want to bump (ramp) spark up below idle rpm.
Does wonders to catch falling idle - acts faster than the under-idle spark ( credit Marcin for this one....I think).