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
Dual ignition an advantage is that if one plug fouls, the fouled plug may burn itself clean while the engine continues running. Wankel engines have such an elongated combustion chamber that even non-aero wankel engines may adopt dual ignition to promote better combustion, in some cases like the Mazda 787B racing car even triple ignition. The MidWest AE series Wankel aero-engine has twin plugs per chamber, but these are placed side-by-side, not sequentially, so their main purpose is to give redundancy rather than improved combustion. Dual ignition Dual Ignition is a system for spark-ignition engines, whereby critical ignition components, such as spark