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Just want to add something in favor of tuners on here. I have logged data with and without a popular tune on here and I also know from asking all major tuners leave timing targets largely unchanged. Under perfect conditions the timing targets were increased by 2 degrees in latter half of power curve but the vast majority of time our ecu pulls timing constantly that it never gets close to hitting new targets. No tuner forces ignition timing like an open loop scenario and since all operation is closed loop, its impossible to have too much timing on these cars if you keep the knock system in tact which all tuners do. It is almost impossible to hit stock timing of 32 degrees.
Also a/f is really unchanged or barely. In my view power increase often happens in mid range and is more a result of vanos timing overlap adjustment and timing in midrange but again since closed loop occurs if the conditionsxarent right it won't hut stock timing let alone higher values. Vanos for all intents and purpose provides a mild camswap without changing hardware. You can change durations and overlap like a performance can would. There is a limit but anyone who has done a small can improvement in older car sees 15-20 HP which is what most M3 tunes produce.
Imo BMW leaves room on the table for cam /vanos tuning is stock settings are emissions driven to some degree in terms of overlap and duration. However changing these really don't out any risk of detonation, esp since gains cone mid range to high rpm which at 4500 plus rpm, things already moving fast enough where preignitiin is unlikely and this no detonation.
Anyone who has logged sews ecu is constantly pulling timing almost always. Only in sub 70 degree weather with newer spark plugs and 93 plus octane have I ever it max timing targets.
So in my view it only makes sense detonation would be problem with FI where detonation can occur for reasons other than preignition due to blower creating crazy high cylinder pressures vs NA where detonation exclusively comes from preignition which other than lugging motor, doesn't happen when engines spin to 8400
One note also you can't sat 12:1 cr can't run 91-93 octane although I agree you can't quite hit max timing but you have too look at 2 important things. First is effective dynamic CR which varies drastically between different static 12:1 cr engines. Second is rpm operation of engine because at 5k plus preignition simply has no time to occur and that's why spinning ahigh cr engine to high rpm allows for high cr as no time exists for ignition of unburned fuel by heat or hotspots.
By more aggressively setting cam timing analogous to putting in larger cam, the dynamic cr is even smaller because as the intake valve remains open longer, it will allow fas escape even past BDC and thus no true compression occurs at a 12:1. variable car is often 7-8:1 for a static cr of 12::1. So tuners can " lower" the dynamic cr by increasing cam durations and thus can often hit higher ignition targets mid range than stock and is why most increase comes from mud range. At higher rpms this effect is less relevant because intake air under higher ROMs is being sucked in with more vacuum pressure and thus air cannot exit back out of cylinder out intake valve when incoming air pressure is higher at high rpm.
My point, a static cr of 12:1 is quite meaningless and until someone accounts for dynamic ratio including intake valve duration, intake and cylinder design from swirling to cooling, and exhaust valve gas flow which allows even more expulsion of gases and more intake vaccum and higher tolerance of higher cr without gas reversing flow leaving intake valve ( is cat less cars tolerate higher CR due to this more efficient expulsion and secondary I'm proved intake. Vacuum effect on dynamic car
12:1. Is meaningless in my view as any way to dictate detonation risk
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