figuring out advance timing
@champyfz450
I can’t really add much to what
@Mattax posted, he’s spot on. Quantifying your results will be the most difficult part of cruise tuning, and what you’re looking at will be mpg and “feel” which both aren't very quantifiable. Don’t worry too much about what your table looks like when you begin tuning. You can go back after the fact and smooth or interpolate the table and make it look better in the 3d model. Sharp spikes or dips are generally not what you’re after. I will say datalogging and overlaying the log on to the base map is the easiest way for me to see what is happening “right now” rather than tuning live. Don’t forget to go back and look at fueling after making timing changes in certain ranges, as both will affect each other.
Thanks. I figured you know EFI and 360s.
@champyfz450
I'd say for steady cruising, inch toward the limits I mentioned above. Too lean at steady load (interstate cruise) the engine will surge and too much timing you will hear (and can also be seen on the spark plugs). Back off as much as two or three degrees from too much timing advance at cruise. This will help account for when the engine really gets heat soaked on a longer trip.
Starting and Idle:
I see no reason to have that much timing when starting. It ran with less than 10 , so 12* should be fine for cranking speeds (under 500 rpm).
Over 20 is just going to be hard on the starter.
At idle rpms, 600-900, that cam shouldn't need 22* unless running it lean, or compression is low.
I
f its an automatic transmission, test the same as with a carb & distributor.
As it is now, put it gear and see what rpm it drops to. Write down the rpm in neutral and in gear. If available, note the MAP in gear.
Then take 2* out of timing. Put it in gear and see if there is less drop in rpm. Less drop demonstrates more power.
Do the same removing 2* more so its at 18*.
For both 20 and 18* experiment with a little richer mix than current.
Try going richer first in a couple of increments. If not seeing any more power, then go leaner. Go leaner in small steps as power will drop off more quickly going leaner. If you've set idle mix on a carb, you've probably experienced that.
When power drops off (as demonstrated by lower rpm and vacuum (higher MAP)) note that, and make it a bit richer.