DIY PROMDo It Yourself PROM chip burning help. No PROM begging. No PROMs for sale. No commercial exchange. Not a referral service.
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Well, I've put maybe 100 miles max on my setup. I seem to have the fueling good so I can go around datalogging. The big thing is I'm running a 730 ECM with the $59 code. For some reason this setup is acting REAL funny with my knock sensor. As I've posted before a histogram of the knock counts goes up to 65k and then drops, repeating infinetly. I can mount it anywhere else I can think of without pulling the engine. When I run it on the highway with my current .bin I think I hear an audible knock at certain RPMS. I of course back right out of it when that happens. Its hard to decern real knock over my hooker 2210 LT's, 4" mufflex and flowmaster muffler. All this on top of my blower whine at highway speeds.
I want to know what is a good approach to developing a spark table / map. I've modified the stock 8D spark table and know how to plug read. Is that an approach? I don't want to spend all this years driving season developing this.
Blown87, thanks for that...that's excatly what I was hoping to learn. For some reason everything seems to click except for spark advance. What you just showed seems to be a very clear explanation as an initial approach.
A lean mixture is more likely to explode than just burn and will burn hotter.
A rich mixture burns slower and also cools the cylinder which would allow for more advance.
Try it out and post back. It wouldn't be the first time I was wrong.
Also way rich and way advanced will hide detonation which will destroy pistons. This is per Grumpy (rip). Do a search and read Grumpy's tuning stickies. The man was way smarter then me, had his own ECM simulator to test new programs. He put in a lot of hours/days just to learn how things worked and was nice enough to share.
A lean mixture is more likely to explode than just burn and will burn hotter.
A rich mixture burns slower and also cools the cylinder which would allow for more advance.
Try it out and post back. It wouldn't be the first time I was wrong.
Also way rich and way advanced will hide detonation which will destroy pistons. This is per Grumpy (rip). Do a search and read Grumpy's tuning stickies. The man was way smarter then me, had his own ECM simulator to test new programs. He put in a lot of hours/days just to learn how things worked and was nice enough to share.
You are right on all you said , expecially on Bruce (rip).
Pandin, no offense
My "depending on the goal" was referred to the fact that often different goals have different solutions.
Let me explain (knowing I'm italian and my english is poor):
Let 's say we need (as goal) fuel economy:
cruising at 60 mph I put a commanded real AFR of 15.5.
In order to achieve my goal a commanded 34 degree advance probably is not good and something near 40 with low loads is better.
Often lean mixtures require more spark advance than rich ratios.
Often rich mixtures require less spark advance than lean ratios.
Say you have to fight a spot (at WOT where you are sure the AFR is good and more in the rich side than the lean), and you are experiencing knock in this spot.
The goal is to be more safe.
You remove spark in a rich situation and the goal is reached.
On both examples we removed spark in a rich situation
and added spark in a lean one.
What I wanted to say with "... depending on your goal" is that not always unmistakable and obvious statement as " More fuel (richer) more adv,
leaner less adv" -on wich I truly agree-, are real on 100% cases.
-Beppe-
This is all great info. I'm starting to be able to visually imagine what my engine wants for spark. That sounds odd but I can now look at my VE tables, print them, come up with a basline spark map, load it up in the Ostrich and then see what the engine really wants from that baseline. I'm certainly in a better situation than I was a week ago.
I don't really care too much about fuel economy otherwise I wouldn't have built what I did. I am however VERY concerned on knock knowing I could blow up a relatively expensive set of forged pistons or worse. I want to keep knock at bay when I'm in the high map high boost areas obviously.
As for the "rich vs lean", in the WOT example more fuel will also reduce the knock. But which was too high, too low, fuel or adv. This is a "in my opinion".
Look at all the rules presented, at wot and cruise, load is the big dog.
What I was presenting was general rules of thumb, guide lines so to speak. There will always be "exceptions and contradictions" always.
This is all great I think to outline a "baseline" approach. My setup is obviously radically different than a stock 91 L98 setup and I don't feel comfortable building off that spark model. I did try it and quoting Grumpy I let the engine tell me what it wanted. What it wanted seemed so far of bat to the stock spark map I wanted to take a step back and look for a "guideline" on how to approach.
