Our cars already have alot of advance at low boost levels and the ECU retards it at higher boost to prevent knock....advancing the timing is a easy way to get some extra power (expecially in the N/A), what it does is it makes the fuel start burning sooner as the piston is making the trip up and compressing the mixture in the combustion chamber, the fuel is suppose to burn and not explode, so for that split second before the piston reaches the top of its stroke the spark plug ignites the fuel and by the time it is done burning the piston is pushed down by the burnt gases. So if you advance it to the point that the piston is at the top of the strock as when the combustion chamber has fully egnited then that is when you would get the most power out of the engine, but if you advance it too much then you get KNOCK cause the explosion in the combustion chamber is forcing the piston down while it is still going up...and that is BAD...