Originally Posted by smufguy
not entirely. spark adv with leaner AF ratio gives you more response but it also drops the exhaust gas temperature. But this also leads to overheating under continueous heating. Also spark advance is good to make more power cause it lengthens the total time of combustion which also reduces the CO and HC emissions, but increases the NOx emissions cause of the prolonged combustion time. As a matter of fact, if you knew anything about engine dynamics or have taken a class regarding internal combustion engine, you will know that ignition advance, is actually a complex activity that not only depends on the engine load but it also depends on how the engine is used.
This might be kinda out of place, but the rally cars retard their ignition timing 40deg on turns and causes the combustion to occur in the exhaust manifold to keep the turbo spooling. Weird, but this is to point out that the ignition settings depend on the usage. ;)