This is highly experimental.
(If it proves to be accurate, it will be added to the official ROM definitions.)
What follows is a condensed version of this thread in the ECU analysis forum.
The ECU’s calculation of “Final Fueling Base” contains a few compensations that are added to the primary fueling enrichment. One of those compensations, here dubbed Delta-Load Compensation, or “DLC,” is responsible for an excessively rich condition during spoolup.
The DLC parameter itself is calculated from four input parameters:
|Input A||Change in load since the previous iteration|
|Input B||Change in load in the previous two iterations (clamped between −0.2 and +0.2)|
|Input C||This is a function of input B and two or three tables, see below.|
|Input D||This is a function of input A, one of two scalars, and a table.|
(I suspect that the ECU’s iterations are 7 milliseconds apart, but I don’t have solid evidence to support that claim. I just know that it contains a counter that increases at roughly that rate.)
Input A is multiplied by another value to become Input D. That ‘other value’ may be 0.1, 0.03125, or a value that depends on RPM. The conditions that determine the multiplier have not yet been studied.
Input B is turned into Input C through a series of operations, starting the “Delta-Load Sigmoid” table, shown here…
The transformed Input B is then scaled by one or both of the tables shown below. The table on the left is always used; the table on the right is applied when load is falling rather than rising. The tables are “DeltaLoad Input C Rising Load Compensation” and “EC2 Input C Falling Load Compensation” respectively.
Inputs C and D are each scaled by Engine Coolant Temperature (ECT) compensation tables, and the resulting values are added together to form Enrichment Compensation 2:
EC2 = (InputD * EctMultiplierD) + (InputC * EctMultiplierC)
EctMultiplierC is strictly a function of ECT, and there are separate tables for rising load and falling load (rising is on the left in the picture below).
EctMultiplierD is a function of both ECT and load (grams of air per combustion charge).