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
Calculated Ignition Index and CCAI are calculated from the density and kinematic viscosity of the fuel. Formula for CII: Where: D = density at 15°C (kg/m³) V = viscosity (cST) T = viscosity temperature (°C) CII was designed to give out numbers in the same order as the cetane index for distillate fuels. Calculated Ignition Index The Calculated Ignition Index (CII) is an index of the ignition quality of residual fuel oil. The running of all internal combustion engines is dependent on the ignition quality of the fuel. For spark-ignition engines the fuel has an octane rating. For diesel engines it depends on