Precision Turbo and Engine BigStuff3 GEN3 PRO SEFI (LS1) System Hardware & BigComm Software - Manual (Page 77)

BigStuff3 Pro SEFI System (LS1)
Version 1.0 76
MAP Transient Fuel: MAP (+) Transient Fuel can be compared to a carburetor’s power valve.
It is used to increase the base fuel pulse width when the manifold pressure increases significantly
for a slight change in throttle opening. MAP (-) Transient Fuel is used to decrease the base fuel
pulse width when the manifold pressure decreases significantly as a result of the throttle blades
being closed.
The MAP (+) and (-) Transient Fuel control is comprised of 5 primary tables and 1 secondary
table. Each of the tables play an integral role as to how the base fuel pulse width will be
increased or decreased for a given change in manifold pressure. Below, is a description of how
and when each of the tables is used by the ECU.
From the tool bar on Main Menu screen, left click on “Transient Fuel”. The screen below will
open. The following paragraphs will describe how to calibrate each of the Transient Fuel drop
down selections.
49. dMAP Correction (F10 – “Quick Key”)
The first table is dMAP Correction. It is used to determine the percent fuel correction, either
positive or negative, for a change in manifold pressure (dMAPdt). The ECU calculates the
change in manifold pressure every 52 milliseconds (ms) as long as the throttle is moving. The
ECU will increase or decrease the base pulse width relative to the dMAP Correction table’s %
correction value (i.e. 100%).
Changes in MAP need to be compensated for by increasing or decreasing fuel synchronously to
the base fuel pulse width. Each cell in the input table represents eight (2) kPa increments.
While the engine is running, a “real-time Ellipse” will move within the dMAP Correction table
relative to the current % Correction “operating point”!! Use it as a point of reference to help
calibrate the dMAP Correction table.