Closed Loop Lambda Long Term Trims is a function that looks at the Closed Loop Lambda trims and states to increment or decrement values in either 1 (for single bank) or 2 Trim tables which over time should reduce the need for Closed Loop Lambda trims and indicate possible improvements to the Fuel tuning.
A quick summary of how it works is if the calculated CLL fuel correction is larger than a particular threshold the cell in the LTT Table that is the closest to the current engine conditions is incremented (or decremented if less fuel is required) by a set amount. This acts as a slow integral of the CLL Trim required on a cell by cell basis.
Note: The CLL Long Term Trim Corrections are applied in addition to the CL Lambda Fuel Correction values.
The LTT Mode setting can be set to OFF, ON or Disabled. When set to ON and CLL is active the CLL Long Term Trim Table (and CLL Long Term Trim Table 2 if using 2 bank CLL) values are incremented and decremented where required.
When set to Disabled the tables remain but no modifications are made to the tables.
Trim Limit Min & Trim Limit Max
These settings are used to set the maximum and minimum values that the ECU can put in the CLL Long Term Trim Tables and the maximum Long Term Fuel Trim that can be applied.
The Long Term Table correction is applied in addition to the CL Lambda Fuel corrections and when using 2 banks is split between the injectors in the same manner.
CLL Long Term Trim Table & CLL Long Term Trim Table 2
These are the tables that store the long term trims, it is recommended to have the axes setup the same as or similar to the Fuel Table so trims are easily transferable.
If using 2 Banks one method of applying the calculated trims to the Fuelling would be to use the Fuel Table for Bank 1 and use a single Individual Cylinder Trim Table on all Bank 2 Injectors applying the difference between the two CLL LTT Tables to this ind cyl trim table.
Note: These tables are stored in non volatile memory and so any trims added by the ECU remain over ECU power cycles. To clear these tables select the entire table and set to 0 (or set the Mode to Disabled to temporarily stop using and altering the values).