Desired Airflow

[Thumper]

Hi Guy's
Another noob question from me.
In the description of 'Desired Airflow', it give the following description.

Used to reduce airflow as the engine warms up.
Although listed in the "Idle" section, this calibration also controls the base airflow for non-idle conditions.

By non-idle Im assuming this means the general running of the engine.
My question is, what else does the desired airflow effect. Does it affect the VE table at all? If I adjust this, how will it affect the overall running of the engine?

thanks guys

[TAQuickness]

This table has direct control over the IAC stepper motor or ETC (if equipped with ETC, IAC motor is not present). The values in this table represent the base required airflow for the engine to maintain idle RPM at given ECT's. This also serves as the "park" posistion while the engine is running.

[Thumper]

So it has nothing to do with Non-idle conditions?

[SSpdDmon]

So it has nothing to do with Non-idle conditions?

Think of it this way...

In order for the engine to stay running, it needs a certain amount of airflow aside from what you give it with your right foot. This table defines that amount of airflow.

When they talk about idle vs. non-idle, it's regarding the PCM's understanding of what idle vs. non-idle is. In other words, check your Idle>General>Parameters. Conditions to meet "idle" are based on TP% and MPH. These conditions control whether or not (what I like to call) the active idle controls are enabled/disabled. When they are enabled, the PCM will adjust airflow (via the IAC valve) along with ignition timing (spark) to control engine speed while learning any adjustments (trims) that need to be applied to the desired airflow table. If the desired airflow values are too high, idle trims will go negative and vise versa. When the active idle controls are not enabled, your engine speed (while off the throttle) is controled by the learned desired idle airflow (desired airflow plus trims), the throttle cracker tables, and either the base or high/low octane spark maps (depending on the settings in Spark>General>Parameters). On the throttle, additional airflow is provided by the throttle follower. So, setting this table is pretty much a totally seperate part of tuning from the VE. VE is technically fueling related where as this is more related to operational airflow.

That, in a nut shell, is how it works.

[Thumper]

Nice, thank you, makes things clearer now.
So another question then.
Does the PCM switch from the Desired airflow to MAF or MAP when the non-idle conditions are not met?

Thanks again for the replies!

[SSpdDmon]

Nice, thank you, makes things clearer now.
So another question then.
Does the PCM switch from the Desired airflow to MAF or MAP when the non-idle conditions are not met?

Thanks again for the replies!

You're talking vowels and consonants...

Again, don't confuse desired airflow with fueling-related parts of the tune. Desired Airflow is there to help determine the amount the IAC valve in your throttle body opens. The PCM is told "x" grams/second equals "y" IAC steps in the Idle>General section, which has nothing to do with MAF, MAP, or VE settings - which are primarily fueling related.

[Thumper]

Understood, I got you now. Cheers thanks alot

[SSpdDmon]

Understood, I got you now. Cheers thanks alot

No problem.