Precision Turbo and Engine BigStuff3 GEN3 PRO SEFI System Hardware & BigComm Software - Manual (Page 83)

BigStuff3 Pro SEFI System
Version 2.1 – February 2011 76
44. IAC Gain Terms
This input table allows the user to set how quickly the IAC motor moves (in or out) in a given period
of time. Use the default settings that come with the ECU unless it becomes necessary to control the
IAC motor speed. The Proportional Gain setting should be from 4 to 16. The Derivative Gain should
be ¼ to ½ of the Proportional Gain. Enter the desired value in the table and left mouse click OK to
save the information.
See Throttle Follower & Idle Spark Table Setup Tips
section directly below for more information on
how to use the “Idle Spark” control, in combination with the “IAC Start Position”, to improve overall
idle control.
Throttle Follower & Idle Spark Table Setup Tips
This brief tutorial will outline how to set the IAC Throttle Follower and Idle Spark tables to ensure
engine idle stability, under various engine operating conditions.
Setup Steps
1. Run the engine until it reaches its normal operating temperature.
2. Hook up the PC to the GEN3 ECU, and make sure communication is established.
3. Zero out the Idle spark calibration. From the main BigComm tool bar, go to Idle, then Idle
Spark in the drop down menu.
4. The following process steps are iterative. The goal is to decrease the ignition timing in the
spark map while opening the throttle blade to maintain the desired engine rpm. When the
timing in the spark map is decreased, the engine RPM will also decrease below the desired
level. To offset the drop in engine speed, the throttle blade set screw will need to be adjusted to
increase the engine RPM back to the desired level. The task is to get the spark timing to about
10 degrees while maintaining the desired idle RPM (at normal engine operating temperature).
The cells below and around the obelisk (the floating football shape), will be used. See the
example screen print below.