How about the sensitive engine to knock

How much we can go rich to prevent knock and achive more power ?

Adding more fuel cools the combustion charge, this is because fuel is a better thermal conductor compared to air. Allowing heat to be removed from things like valves, cylinder walls and the air itself.

Reducing charge/combustion temperature helps reduce knock, this will then let you either add more timing to gain more cylinder pressure and more torque/power.

There is always a point though where adding to much fuel will then reduce torque/power and possibly start to misfire and poor economy. The key is finding that balance.