Startup Airflow and Startup Friction Airflow whats the difference

[carneb]

The tuning tool gives a good description of the Startup frictional airflow correction, but what is Startup airflow correction. I've logged both IAC_SUP_DMA and IAC_FRICTION_DMA during startup. IAC_FRICTION_DMA corelates closely to B4343 but IAC_SUP_DMA bears no relation to B4304. In fact, while logging today I noticed that the PID's for friction and startup airflow were giving identical figures in my logs. Is this how it is supposed to be or is something funny going on?

[Tordne]

LOL - I asked the exact same thing a few weeks back :)

[TAQuickness]

IIRC, Friction airflow decays a bit faster than startup airflow. It's there for the little extra omph you need for cold startups.

[SSpdDmon]

I see it as they are both doing the same thing - temporarily increasing desired airflow. It's like the engineers had to increase airflow during startup accounting for two different things here.

Since the motor temp will have a direct reflection on oil temp and how fast things can become lubricated (please...no dirty jokes :) ), the Startup Friction Airflow adds a little to the Desired Airflow to keep the motor from stumbling/stalling because things aren't coated with oil completely. Remember, colder oil is thicker and doesn't penetrate the cracks/crevises as easily (that sounded dirty...my bad).

The other side of it is Startup Airflow - a motor naturally needs a little more airflow temporarily during startup. That's why this table doesn't have any delay before it begins to decay and decays at a greater rate. It's not waiting for the oil to warm up. Older cars used to start easier when you pump the pedal a little while it's turning over. The PCM is just doing it for you with this table.

That's my logic...

[carneb]

That's a good explanation SSpdDmon. The thing I don't get is why the values for Startup Airflow I'm logging are the same as Friction Airflow and bear no resemblance to the values in the Startup Airflow table?