Anyone knows a thing or two about ignition timing?
I've been playing around with MegaJolt again, finally got it running this time (albeit without a rev limiter, messed up the wiring on that one, have to re-do it a bit).
I will eventually get it on the dyno for fine tuning of course, but for now I want to get a feel of what's involved and play with a safe map.
What I gathered so far: more RPM = more advance, higher load = less advance. If I understood correctly, the first has to do with increased piston speed while the mixture burning time stays constant, and the second has to do with more efficient and faster burning at higher manifold pressure.
Here's one map I found for my engine. The load is estimated with a TPS rather than the MAP, 100 being the highest load. I'm puzzled about how advance goes up and then down with load increase. For loads 20%-100% the profile follows the rules, but for the lowest load the advance is reduced, what justifies that?
My stock distributor has a mechanical advance, no vacuum. I'm thinking about mapping its curve with a stroboscope gun and starting from there, taking clues from the map above.
EDIT: Found this method of adjusting the advance without a dyno:
The way I approach it is to start with a solid base map with areas of boost tending towards the retarded side. I then utilize a set of det-cans to listen for knock as I slowly increase timing while cruising in 4th gear(1:1). So do a pull-> slow down -> increase timing -> another pull & listen for knock -> Slow down -> Adjust timing -> Repeat.
Once I start to hear detonation, I pull timing anywhere from 2-7 degrees depending on how intense the knock is and where in the timing map I am (higher rpm/load or lower).
Sounds pretty brutal
That's 100 runs times however many adjustments / cell is needed to find the detonation point. How is it done at the dyno then? I guess one can drive the load to a particular cell and slowly adjust them one by one. But what are the criteria? Detonation as well?
