High boost low timing - low boost higher timing

What would be considered the acceptable lowest ignition timing in the upper rpm range when tuning , obviously lower timing numbers will have high egt , as a rule of thumb should 5500-7000k rpm range be no less than 6-8 degrees? For say 1.6 bar boost on a 2.0 turbo , or would 2-3 degrees ignition also at this rpm be too low with 1.9-2.0 bar boost . What I mean is at wot , will the lower timing number not have way too high egt ? At what point do you draw the line with your low timing ? I'm talking here also when restricted to low octane fuel .

I've come across some oe tunes running 4 degrees at redline 6-7k rpm with lambda 1 , di engines .

As far as ignition timing goes you always want to get as close to MBT point as possible providing there is no knock occuring as you are trying to get to that point. If you are limited with low octane fuel you'll definitely need to retard ignition timing which will result in higher egt as you said. Usually it takes quite a few wot pulls to find acceptable combination of boost, ignition timing and egt, it is always act of ballance with low octane fuel...

With low octane fuel available at the pump it's not possible to get to mbt on turbo charged engines, but what I mean is you when tuning you can either lean to higher boost lower timing or vice versa , but what will ideal minimum ignition be at upper rpm before it gets to risky with egt , would running 2-3 degrees at the upper rpm range be to risky for egt ?

No one's gonna be able to tell you that as it depends on your particular cylinder head condition, physical properties of your particular pump gas, physical condition of your spark plugs, your particular exhaust system, AR and boost of your turbo and so on... There is no general rule but combination of particular things.

As Shota said, "it depends" - different engines and setups will give different results.

Other factors that will give a little more head-room are getting the charge as cool as practical, impellor material - some can give 100C more max' temp, A/R ratio - trading off getting the hot gas out against loss of bottom end and response, camshaft timing to reduce the lower rpm dynamic compression, etc.

Really, though, the primary "cure" is to run a lower static compression ratio - this is trading off off-boost performance for less compressive charge heating, which has a direct affect on the combustion characteristics of the charge.

Forgot, if using an inertial dyno', expect the engine to actually need less timing as in real road and track conditions there will be greater "heat soak" - if you can, log any knock sensors you have.

You’re on the right track with concern about temps, so getting an EGT sensor in place and then testing would be a great next step.

Yep. It will tell you a lot about the quality of your pump gas. For instance, we had changed the gas station and picked up 40 whp using exactly the same tune (except ignition timing) but different pump gas of the same ocatane rating. Needless to say it was so much easier to handle egt...