Pre-ignition Pre-ignition Pre-ignition (or preignition) in a spark-ignition engine is a technically different phenomenon from engine knocking, and describes the event wherein the air/fuel mixture in the cylinder ignites before the spark plug fires. Pre-ignition is initiated by an ignition source other than the spark, such as hot spots in the combustion chamber, a spark plug that runs too hot for the application, or carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events. The phenomenon is also referred to as 'after-run', or 'run-on' or sometimes dieseling, when it causes the engine to carry on running after
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