Well I was just thinking if it was too retarded, the bang is coming way to late, ergo none of the explosive force of combustion is used up in moving pistons, plus the volume in the cylinder is a fair bit higher....creating lean like conditions, resulting in a hotter exhaust gas.
That was my dodgy theory anyways.
Advancing it caused combustion to happen earlier, using more energy resulting in less heat.
How does all that sound...plus I wanted to advance the timing anyway as it was feeling a little lethargic