MichiganSkip

Black line is Spark Advance, Red is rpm and Blue is TPS%
went from 1250 rpm and 60kPa with 37* nailed it and timing went south
1225 rpm at 100kPa and 13* advance. BUT looking at the timing tables, it doing what it's supposed to do. Wonder why GM has it set to do that?

Dan K

So the question is why does timing drop at high map at 1300rpm?

MichiganSkip

Yes, take a look at a stock timing table and you'll see what I'm talking about

Dan K

I know what you're talking about, I've seen enough files.
I was just trying to cut through the fat.
I wonder if this would be something better brought up in Advanced Tech as I'm sure it has more to do with the capability of the engine?
Good question though, as I've never really seen it brought up anywhere.

Injuneer

Just a random thought.... but when you open the throttle at low RPM, density of the air charge increases.... in your case it increased by 67%. High density + matching fuel means high cylinder pressures on top of a slow moving piston. Too much advance and you are certain to see detonation. At more moderate throttle openings, like "cruise" the lower cylinder pressure allows you to put in a lot more advance to increase fuel economy.

MichiganSkip

Fred, you are the 2nd old fart to tell me that Makes sense to me. Maybe that's why I can pick up a good 5 tenths with a converter? Gets me past that rpm point when I nail the throttle.