There are some methods that involve formulas that require specific information about the engine, the fuel, air temp, etc. I don't know any tuners that try to figure it out that way, even so it would still be a guessing game. Fuel is not always rated the same and the internals of an engine can change over time specification wise. Then of course there is the whole complication that comes in with boosted motors and the fact they are effectively dynamic in spec depending on boost and charge temps. If you think about it the variables are so vast its pretty tough to try and "calculate" something.
I think most good tuners from experience have a decent idea of a good starting point that doesn't require large doses of guess work. Pushing a modern day Subaru for instance to a point of slight knock is not really harmful in short small amounts. The feedback knock correction does its job and does it fast.
The knock systems in place on these cars are very effective and even with a good tune conditions may still arise that will force the system to pull timing due to knock.
I can honestly say after tuning for so many years that I still get surprised by some unexplainable differences. Two seemingly identical setups that each respond different enough to require timing adjustment, they do pop up every once in a while. Cobb OTS maps for instance are conservative enough usually to account for these variations but most people will find if you log an OTS map your car maybe trimming back or forward timing automatically. This is all to fit the specifics of that car and its environment.
Originally Posted by Bad Noodle
So I have a question for you guys. When tuning timing, is there a way figure out theoretically how much timing you want to run? I've never like the idea of adding timing till it knocks, then backing off.