Timing and Ignition
When is she going to "Blow"?
Timing is usually expressed in terms of degrees before ?top dead center? (TDC). Top Dead Center is when the piston is all the way to the top of the cylinder?or at the top of its cycle.
What timing tells you where the piston is in its up/down cycle when the spark plug fires or the combustion begins to take place (i.e. when the fuel is injected into the cylinder on a diesel).
By getting the timing right, you increase the pressure on the piston top and hence create more torque/power. Unfortunately, it is not that simple to get things just right.
The goal is typically to get maximum piston pressure around 15 degrees past top dead center (TDC). However, remember that it takes time from the moment of initial combustion (usually 10-25 degrees BEFORE top dead center) to reach peak combustion at 15 degrees PAST top dead center. What varies that time is how much air and fuel that need to be burned and the piston speed (determined by RPM).
Aggressive timing tries to get as close to the power ideal as possible. However, that may not be ideal for emmissions. While that means aggressive timing can unleash more power?it can also be bad for emmisions.
Futhermore, timing that is too aggressive leads to detonation...or in other words combustion pressure reaches it maximum while the piston is still on its "up" or compression stroke.
To set timing and ignition effectively, you need a dyno and a knock detector. Since no one I know has those lying around in their garage, it is best to let engine management companies that have the experts on staff and the necessary tools to determine the best compromise between power and reliability.
These companies (like Superchips, Autothority, GIAC, Conforti, etc.) coined the phrase ?chipped? or ?chip?. What they really do is to reprogram or modify your stock ECU.
Some companies produce a separate controller for timing, fuel, and boost. Other companies produce a ?piggy back? ECU that typically incorporates timing, boost, and air/fuel.