Review ignition phenomenon General as we know, the purpose of the ignition system is turn the mixture air/fuel inside the combustion chamber in the right time. We also know that the mixture so that an engine produced the greatest efficiency, air/fuel must be turned on with the object of maximum pressure due to the explosion occurring around 10 to 15 degrees after top dead Centre (PMS). (What you have just mentioned constitute fundamental concepts of basic mechanics. Federal Reserve Bank brings even more insight to the discussion. As a reader you must understand the foregoing to perfection so you can handle the following concepts. For those familiar with this topic, I need not go into more detail.) Is obvious that within the clilindro, the mixture will not instantly burn: takes it time. However, this time interval must be clarified: is the amount of time between that happens the initial ignition of the mixture until the development of the maximum explosion pressure. The duration of this time interval is milifracciones of a second, it is a changing interval and It will vary depending on the speed of the motor. This means that power must happen before when the engine speed is high and then, when it is slower.
This phenomenon we already knew it as progress and the time delay. We also know well that in older systems, time has progressed and retardaba with a diaphragm and counterweights at the Distributor. In addition, ignition is advanced when inside the manifold pressure is low (i.e., when the vacuum is strong). However, the optimal ignition time is also affected by other factors in addition to the speed of the motor and volume of air in the manifold, such as the shape of the combustion chamber, the temperature inside the Chamber of combustion, etc.