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.

 

After the Post-Start Enrichment has decayed away, Post-Start Enrichment will turn off and Warm-Up Enrichment will become active. Warm-Up Enrichment will remain active for the rest of the time that the engine is running. As the engine warm-ups up to full operating temperature the required warm-up enrichment will decrease.

 

To complicate matters the required enrichment changes dramatically with airflow. For example with ECT of 20ºC the amount of enrichment required at idle is considerably more than the amount required if operating at half throttle. To allow compensation for this, a 3D Table is used to allow the warm-up enrichment to be set as a function of both engine coolant temperature AND load. It is recommended that one table axis is set to TP(Main), the other must be set to a value that represents engine coolant temperature (usually ECT).

 

The Warm Up Enrichment Table can be set to either Single or Multi Fuel modes:

·Single mode - In this mode there is only one Warm Up Enrichment Table and the enrichment from this table will be applied once Post-Start Enrichment is finished.

·Multi fuel Mode - In this mode there are two Warm Up Enrichment Tables. This mode is only for use when the Fuel Equation Mode is set to Modelled - Multi Fuel. Warm Up Enrichment Table 1 should be tuned to suit the primary fuel, while Warm Up Enrichment Table 2 should be tuned to suit the second fuel. The Multi Fuel Blend parameter will then interpolate between the two Warm Up Enrichment Tables to provide the correct amount of enrichment once Post-Start Enrichment is finished. The Multi Fuel Blend parameter is controlled by the Multi Fuel Blend Ratio Table.

 

Values in the Warm Up Enrichment Table represent the percentage of the base pulse width that will be added to the fuel value. A value of 0 in this table will result in no warm up enrichment. Areas of this table around normal running temperature should be set to zero.

 

The current Warm-Up Enrichment value is displayed on the Fuel tab of the Runtime Values Window (F12 key).

 

 

Note: At normal operating temperature the warm-up enrichment should be set to zero.

 

Note: There are four engine coolant temperature dependant functions which provide enrichment. These are Pre-Start Prime, Crank Enrichment, Post-Start Enrichment and Warm-Up Enrichment. As a general rule, the correct warm-up enrichment value will be lower than either the crank enrichment or post-start enrichment.