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 seasonally by largely mobile peoples in the Early and Middle Archaic periods. Based on the presence of specific plants, the rock shelter was inhabited during the wet season from July to September, then in the Archaic period, around 4700 BCE, from May to October. Some of the earliest known villages appear along sea coasts, specifically the Chiapas and Caribbean coasts. It is likely that the abundant sea and lagoon resources could easily support long-term, year-round settlements, leading people to settle first in these areas. Shell mounds in these areas are highly visible, which likely aided in their identification by scholars.