Seems like the higher I set idle timing...the more pronounced the startup hunting gets.

With 27-28 degrees, it's really bad. 25-26 moderate. And, 24 or lower, much less obvious.

When warmed up, more advance at idle seems more responsive. OTOH, I'm still trying to find the happy medium between idle coolant temps, responsiveness, and smoothness.

Probably due to my advanced cam timing (4-advanced), my 383 is just dog-nuts torquey off the line. Or, even with the lightest tap at normal street rpms. Instant on...Instant go. It's a cool deal. Who doesn't like neck-snapping responsiveness?

The point is lowering some of the lower load timing values does seem to make it run up/down a hair smoother...and seem more like any "other" sportscar. Ho-Hum.

Less timing also cuts down on my 1500-1600 harmonic vibration...probably due to header harmonics. It's fairly mild with lowered timing...and borederline obnoxious with it.

Probably just the "nature" of the beast. Maybe needs to be "cured" thru exhaust iteration #3.

I'm rambling...because the real point is to find that balance between COLD startup stability, too much timing for idle-generated heat, and too little timing where fuel goes into the headers/cats.

I note the AYPY bin uses a lot less timing in those lower value tables. I guess they hold timing up...to balance the automatic in DRIVE. Otherwise, they lower timing to bleed compression for a smoother idle? Maybe even to minimize cam "surge" for easier parking lot crawl.

Next iteration I'll go back to the lower 20's for idle timing. Now, it's 24.5...which seems to have improved the fans' ability to keep it cool at idle. It actually dropped in temps when the fan came on for the last bin.

Scans never showed evidence of lean idle. Plugs looked good too. Hard to think I was running lean at idle...though I suppose it's possible. Wouldn't that mean the 02/ECM weren't doing their job?

 

Have you thought of using the Coolant SA Compensation to reduce timing when motor is colder?

 

Definitely. Have manipulated those values...with everything else -- since learning to tune. Paradox is more added advance in the SA by load/temp table=better startup performance (responsiveness). Except during the first few seconds.

I need to abandon keeping lower 3-4 rows the same value I think. Maybe use offsetting timing between normal and SA by load/temp. Where higher in main table, make is lower in warmup table. Net effect flat timing.

 

You may also want to look at Startup SA Decay Delay and rate if those tables are available in your cal.

 

Good idea. Decay advance so quickly -- as to make it like it was never there!

Brilliant!