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Idle Normalization🔗

The Idle Normalization Module is responsible for determining the idle airflow percentage (the amount of throttle to use when the engine is idling).

It supports both electronically-controlled throttles ("drive by wire") and drive by cable throttles. For drive by wire throttles, the module outputs an idle throttle position (%). For drive by cable throttles, it outputs a number of steps for the Idle Air Control valve.

The process is as follows:

  1. The Idle Integral Term is calculated, based on Idle Trajectory Error and Idle Integral Gain.
  2. This is added to the value specified in either the Idle Airflow Percentage table (when in run mode) or the Startup Idle Airflow Percentage table (when cranking).
  3. The resulting percentage is then checked against Idle Airflow Rate Limiter Up and Idle Airflow Rate Limiter Down to ensure that the airflow does not change too quickly while the engine is idling.
  4. The idle airflow percentage is then checked against the specified Idle Airflow Percentage Maximum and Idle Airflow Percentage Minimum and adjusted if necessary. The final percentage is referred to as Idle Desired Airflow.
  5. Idle Desired Airflow is then converted to the appropriate output for the type of throttle installed.

The module also determines the amount of spark advance to apply when the engine is idling. This task is much simpler. Spark advance is equal to the Idle Proportional Term, which is Idle Trajectory Error multiplied by Idle Proportional Gain.