I'm not sure if a datalog is going to show me anything without a knock sensor. If I had one I think I probably could as I'd be able to check knock against the timing table, but without one I'm not sure what I would compare the timing against. My thought was more if I can get the engine operating at a steady state I could change timing on the fly and see what effect it had. If it likes it I would expect the speed to increase slightly as the engine would be making more power at the same conditions. If it didn't I would expect the speed to drop. Effectively like running the car on a dyno at a constant load and adjusting timing, just doing it on the road instead.
I could maybe do something similar with a datalog where I do a run at one setting, change it, then make the same run and compare the load between the two, but I feel like it would be much easier and more productive to do in realtime as there would hopefully be less variability between runs at that point.