The moment at which the spark plug fires, usually expressed in the number of crankshaft degrees before the piston reaches the top of its stroke.
It is important that the spark coming from the spark plugs ignites the air-fuel mixture at the correct moment determined by the manufacturer of the engine. Often this is a few degrees before top dead center (BTDC). Suppose the specs indicate that it should be set at 5 degrees BTDC, but in actuality it is set at 6 degrees. In that case, the timing is advanced. If it were set at 4 degrees, the timing is retarded. Incorrect ignition timing may result in poor performance and excessive fuel consumption.
Assembling the ignition components (either Magneto or Distributor) ignition such that the spark is delivered to each cylinder at nearly the top of its compression stroke. The timing will usually be at slightly beyond TDC. The terms Advancing and Retarding the timing refers to the relationship of when the spark plug fires to TDC. Ignition timing is different at different RPMs. There is usually a device to advance the timing as the RPMs increase. The faster the engine spins the sooner it needs to fire.
System to ensure each spark plug fires at the correct moment, regardless of engine speed.
The time in the cylinder firing cycle at which the ignition spark (provided by the spark plug) occurs. The spark timing is normally a few degrees of crankshaft rotation before the piston reaches the top of its stroke, and is expressed as a number of degrees before top-dead-centre (BTDC).
The time of occurrence of ignition measured in degrees of crankshaft rotation relative to TDC.
The timing of the spark plug spark in the combustion chamber during the piston's compression stroke. This timing is preset by the auto manufacturer, and in cars with electronic ignition systems rarely needs to be adjusted. In cars with engine management computers and distributorless ignitions, no adjustment can be made.
The timing of the spark, expressed in crankshaft degrees, in relation to top dead center.
Ignition timing in an internal combustion engine is the process of setting the time that a spark will occur in the combustion chamber (during the power stroke) relative to piston position and crankshaft angular velocity. Setting the correct ignition timing is crucial in the performance of an engine. The ignition timing affects many variables including engine longevity, fuel economy, and engine power.
