Hello folks. Got a question here. But lets start with some background....

I finally got a chance to play with my PROM some now that I got my GTA out of storage . I tweaked the injector constants a tiny bit as it was reading a bit high in the BLMs but my main target was to play with timing.

I have 93.5 octane in the car and I have verified that the KS is fully functional in the past (although I didn't see any knock today, it does presently log a couple knock counts on start up from the starter noise so I assume it is still alive and well).

I had my main spark table pretty conservative last year as I was messing with the fuel a lot and didn't want to do two things at once. So I started working up the timing in the WOT region and figured I would see how far I could take it. Well I bumped it up a few times and I started to get real close to where I thought I should see some knock. But I haven't seen anything at all yet. Now here is where my question comes in.

The spark advance, as read from data logs in Excel from Craig Moates software, is 35.2* right now at higher RPMs at WOT. I have the base timing set to 8* and I have the base timing parameter in the bin set to 8 as well (although TunerCat reports the base timing parameter as 8.1* prolly due to some truncating or something). My LV-8 208 column has 30.9 for the last three values right now and my WOT spark advance adder is 4.2 for the last value.

So my question is what exactly does my main spark table mean? If I had 30.9 of advance plus 4.2 advance addition from the WOT adder plus the 8.1 base, that would make 44.2* of total spark.....

That doesn't seem right to me so am I to assume that the base timing is not factored into the advance? That would put me at 35.1* of advance with my main spark table figure plus the WOT spark adder. That makes sense if you assume some truncating issues, but why does Craig's program report it as spark advance? Is that not spark advance that it is reporting? I mean I know my TFS AL heads will take some higher timing than the stock iron heads, but 44* ???? Just doesn't seem to work for me.

So ..... my question is, what exactly is the true timing that the engine is seeing in respect to what you have in your main spark table, WOT spark adder, and the base timing?

Maybe it is just the fact that the base timing is already factored into the main table and the timing that the engine is seeing is what Craig's program reports as spark advance (in the data log I am referring to - hard to stare at the screen when I am hittin WOT and trying to watch for public officials ) but I want to know that for sure.

Well thanks in advance folks,
Laterzzzzz,
Matt

p.s...... I also added some timing to my idle areas (they were at 20*) and that did some wonders for smoothing out the idle.... I have it at 26* at idle but I don't know if I want to go any higher.... Opinions?

 

The timing reported by the CM program (and every other scan tool/program) is the actual timing at the engine, including base timing, main spark advance, PE (WOT) timing, and minus any knock retard. The main spark advance table includes the base timing, so if you have 30 degrees, then it's actually 30 degrees at the engine (8 base plus 22 added by computer). The PE s.a. is added on top of that, so you are seeing 35.1 (30.9+4.2) degrees while in PE mode, not 43.1 (8+30.9+4.2) degrees. With nearly the same engine combination as you, I've found max power at 28-29 degrees total, but I'm also running 11.1 compression.

I do run up to 44 degrees total timing in the light cruise areas, but I have the timing dropping off quickly as soon as the LV8 goes over 96 (the engine doesn't like a lot of timing in lower-rpm mid-load areas). My idle timing is at 30 degrees since I found the most vacuum (used a vacuum gauge) and least amount of airflow there compared to anything between 18 and 30 degrees, but your results may vary.

 

Thanks Greg. It actually started to make a lot more sense to me when I started typing up that thread but I wanted to hear from some more experienced PROM tuners before I went any higher with spark. I haven't run it out all the way through third gear yet (gotta get out of town a ways for that kind of stuff) with this table so I am gonna hold off on the WOT spark stuff until I do. But the added timing at idle rules!! And I drove the car some more this morning and logged data and got no knock at all with my current spark table. I will prolly try some more timing at idle and see what happens....

Laterzzzz,
Matt