

it's not quite that simple,you need to consider the calorific value of the fuel as well.

LPG has good resistance to detonation, but low calorific value so an lpg conversion will normaly give a reduction in power output.

Water has fantastic anti-knock properties, but you dont get much power out of it!
The ideal ignition timing is whatever figure causes maximum bmep.

If you over advance

(even without causing detonation) you loose power, it's not a simple case of more advance=more power.

The timing needs to be advanced

(before) tdc to allow time for the flame front to propogate, since it takes a finite time we need increased advance at higher revs.

An engine that needs an extreeme level of advance is likely to be suffering from other combustion problems

(usualy poor scavenging caused by bad exhaust manifolding) that cause uneven flame propogation.
