Ignition timing Ignition timing In a spark ignition internal combustion engine, Ignition timing refers to the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke. The need for advancing (or retarding) the timing of the spark is because fuel does not completely burn the instant the spark fires, the combustion gases take a period of time to expand and the angular or rotational speed of the engine can lengthen or shorten the time frame in which the burning and expansion should occur. In a
Mesoamerican Archaic period differed regionally. Most Archaic sites are not very well preserved or visible, which hampers archaeologists' ability to discover and study Archaic period sites. As a result, not many Archaic sites have been identified, although major sites like Guilá Naquitz and Colha have been explored by archaeologists. Most known Archaic sites are in the Mesoamerican highlands or along the coasts, though there are sites throughout the region. During the Archaic period, Mesoamerican peoples slowly changed from being nomadic hunter-gatherers to semi-sedentary or sedentary foragers and farmers. Based on research at sites on Mexico's gulf coast, central highlands, and coasts, it seems