[serialk11r]

Hmmm...there definitely is a speed below which you could accumulate some bearing wear every time the throttle is tapped to raise the engine speed. I doubt it's above 500rpm though, because engines have some lugging resistance designed in, and most engines can be run at full throttle at 1500rpm or lower. I would turn down the idle speed until one of the following happens:

1. Fuel usage stops going down despite decreased speed (unstable combustion)
2. Not enough electrical power generated to at least provide some charging for the battery
3. Engine sputters on transient load instead of quickly revving up.

Pretty much every modern car is able to idle at 650 and most "normal" 4 cylinder cars can idle at 600 if you ask them to.

Timing wise, I think the principle of operation should be "perfect is the enemy of good enough" (you can be off by a degree or two, maybe more, and not have noticeably less power), and extrapolate as much as you can based on maps you can find from other engines, and use reaction rate chemistry from high school to help you extrapolate based on load, temperature, lambda, etc.