Precision Turbo and Engine BigStuff3 GEN3 PRO SEFI (LS1) System Hardware & BigComm Software - Manual (Page 72)

BigStuff3 Pro SEFI System (LS1)
Version 1.0 71
The bi-directional input table allows the user to quickly advance the timing (left side of the input
table) when the RPM begins falling below the “Desired RPM” setting. Once the timing is
advanced it needs to be retarded (right side of the input table) as the engine RPM begins
increasing. The zero point in the table is equal to the user defined, “Desired” RPM.
While the engine is running, a “real-time Ellipse” will move within the Idle Spark table relative
to the current RPM Delta “operating point”. Use it as a point of reference to help calibrate the
Idle Spark table.
To change a value in the Idle Spark table, move the cursor using the PC’s mouse or arrow keys
to the cell to be changed. Input the desired value and hit ”Enter” to save the change.
The values shown in the table below can be used as a baseline.
43. IAC Start Position
A general description of the IAC motor and valve (plunger) was described above in the “Throttle
Follower” paragraph. The IAC motor can be in one (1) of one hundred eighty (180) potential
positions, from fully open to fully closed. Fully closed would represent position number one and
fully open would represent position number 180. The ECU monitors key engine operating
conditions and positions the IAC valve (plunger) accordingly. When the engine is shut off, the
IAC goes to position number zero and then counts back to position number 90, or half way open,
and stays there. When the engine goes into cranking mode the ECU reads the coolant
temperature and instructs the IAC what position to go to. Based on user defined inputs, the IAC
Start Position Table allows the ECU to position the IAC valve to a predetermined position
while the engine is cranking, so that when the engine starts the idle speed can be quickly reached
and maintained.