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
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