Cold engines require significantly more fuel (enrichment) than warm engines. This is primarily due to the fact that the injected fuel condenses on the walls of the inlet tract and therefore does not make it to the cylinders.
The Crank Enrichment function provides enrichment while the engine is being cranked on the starter motor (while the engine speed is below 400rpm). As soon as the engine speed exceeds 400 RPM, Crank Enrichment is turned off and enrichment is provided by the Post-Start function.
The amount of crank enrichment that is required for starting depends on engine coolant temperature, to cater for this, an 18 cell table is used to allow the crank enrichment values to be edited in 10ºC increments. The value entered into each cell represents the percentage enrichment at that particular temperature. Linear Interpolation is used between each cell to calculate the crank enrichment when the current engine coolant temperature is between the cell centres, the green cell indicates the currently active cell.
The current amount of Crank Enrichment is displayed on the Fuel tab of the Runtime Values Window (F12 key).
Crank Enrichment Settings
This setting adds to the Crank Enrichment for the FIRST engine revolution delivering an additional enrichment just for the first revolution. Do not confuse this with the Pre-Crank Prime setting that delivers fuel BEFORE the engine is cranked.
Set this to ON for a Crank Enrichment Table that has x and y axis. Set to OFF for a Crank Enrichment Table with only an x axis.
Sets the percentage of fuel enrichment that will be applied when Crank Enrichment is active. If only using the x table axis set the axis to Engine Coolant Temperature (ECT).
This is the time in seconds that Crank Enrichment will continue to operate after the ECU has crossed over to Post-Start Enrichment. This means that for this period of time both enrichment functions are operating at the same time. This function helps to provide a more stable air fuel ratio in the first few seconds after startup.
Note: There are four engine coolant temperature dependant functions which provide enrichment. These are Pre-Crank Prime, Crank Enrichment, Post-Start Enrichment and Warm-Up Enrichment. As a general rule, the correct crank enrichment value will be higher than either the post-start or warm-up enrichment values.
