Date: 9/12/18
By: Mike McGinnis
Vehicles affected:
Software affected:
Firmware affected:
COBB has identified the lean limit tables as causing behavior Protuners do not expect, and we'd like to help you better work with them and understand how they work.
In order to do so, the table names and look of the tables has been updated.
"Closed Loop Fueling Target Base (Main) Lean Limit A-D (Coolant Temp)" has become "Closed Loop Fueling Target Base (Main) Lean Limit and CFF Transfer Modify A-D (Coolant Temp)".
Rather than an air/fuel target, the Z data is being presented as an air/fuel target adder. As with many adders, you can zero the Z data out if you want to "disable" the adder, preventing these tables from impacting fueling. If that is your goal, you can skip the rest of this bulletin which explains how to tune these tables using non zero values.
The lean limit tables manipulate how the final closed loop fuel target is applied to commanded fuel final. As a reminder, commanded fuel final, or CFF for short, is the final fuel target for injector pulse width (IPW) calculation.
Here are some examples of how the lean limit tables can impact fueling:
WARNING: The manipulation of the transfer of the final closed loop fuel target to the commanded fuel final target by this table can cause more positive fuel trims (i.e. lean condition) in closed loop when this table is greater than zero (or more negative fuel trims when the table is less than zero). Care should be taken when tuning this table to non zero values, especially where it would be active at higher loads in closed loop.