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
Archaic humans Archaic humans A number of varieties of "Homo" are grouped into the broad category of archaic humans in the period contemporary to and predating the emergence of the earliest anatomically modern humans ("Homo sapiens") over 315 ka. The term typically includes "Homo neanderthalensis" (430+–38ka), "Denisovans", "Homo rhodesiensis" (300ka–125ka), "Homo heidelbergensis" (600ka–200ka), and "Homo antecessor". There is no universal consensus on this terminology, and varieties of "archaic humans" are included under the binomial name of either "Homo sapiens" or "Homo erectus" by some authors. Archaic humans had a brain size averaging 1,200 to 1,400 cubic centimeters, which overlaps with the range