Precision Turbo and Engine BigStuff3 GEN3 PRO SEFI System Hardware & BigComm Software - Manual (Page 82)

BigStuff3 Pro SEFI System
Version 2.1 – February 2011 75
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 the ellipse 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.
See
Throttle_Follower_and_Idle_Spark_Setup below for more information on how to use the “Idle
Spark” control in combination with the “IAC Start Position” to improve overall idle control.
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.
The “position” values shown in the table below can be used as a baseline for most applications. You
can see from the large values in the table that when the coolant temperature is cold, the IAC seeks a
position in the direction of the fully open position (position number 180). As the engine reaches
normal operating temperature, the IAC finds the position that allows the engine to idle at the user
prescribed “Desired” idle speed.
While the engine is running, a “real-time Ellipse” will move within the IAC Start Position table
relative to the current engine Coolant Temperature “operating point”. Use it as a point of reference to
help calibrate the IAC Start Position table.
To change a value in the IAC Start Position 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.