Ryan
May 31st, 2008, 03:55 PM
Before anyone feels tempted to post a link to the RAFIG tutorial, please don't. I've already been through it.
Now, I am running a 98 PCM with an A4 and a healthy sized cam. The tune is currently set to OL with MAF enabled (and solely MAF after 1200rpm). The MAF curve provides a reasonably accurate AFR.
My problem lies with the desired and reported airflow values. At the desired idle RPM in Park or Neutral, the car idles properly around 8g/s of airflow. Following the RAFPN table, the PCM thinks the car wants ~2g/s (after ST/LTITs). The values I use in B4307 seem irrelevant, as the PCM constantly reports to want some absurdly low amount of air. Regardless of where the values in B4307, the car still will swing right to 8g/s. The airflow values I am given to use from the trims are nonsensical, and constantly want extreme adjustment. I am right around 80 IAC steps at hot idle.
Now, when I shift into gear, the IAC immediately opens almost all of the way (sometimes it goes to the max of 310 steps). This is highly annoying, as the car has to sit still for some period of time to "learn" back downwards. If it moves before it's learned completely, the idle flares back up to ~1400rpm. The RAFIG process results in the same odd values. The car thinks it wants >22g/s in gear, but idles at the proper rpm (once it learns down) around 11g/s. No matter what values I put in B4307, the car wants more air. If I put what it wants (22g/s), it shows IACDES_B to want 26g/s. As soon as a gear is selected, the desired airflow jumps up, as do the reported airflow values (although they do not go as high). Even after learning back down to the proper rpm, IACDES_B shows some apparently ridiculous number (the learned values also have no effect in B4307).
The trims always point to some nonsensical value. I can't get the desired airflow values (IACDES_B) to match the values in B4307, and I can't get the idle trims to be reasonable.
I have played with the "Idle" section extensively, with no avail. Clearly, the desired airflow values are no reasonable.
Things I know:
The IAC motor is not sticking, nor do I have vacuum issues. I am not confusing units. The fueling at idle is (relatively) normal. B4307 seems to have no effect on IACDES_B. I have not found any PID that seems to add the values to IACDES_B on top of the B4307 (such as throttle cracker/follower, startup friction, etc.).
What tables/parameters effect IACDES_B (or: how can I fix this)? My current tune is attached, and I can gather a log of any PIDs suggested. I've described the behavior shown in my various scans.
Now, I am running a 98 PCM with an A4 and a healthy sized cam. The tune is currently set to OL with MAF enabled (and solely MAF after 1200rpm). The MAF curve provides a reasonably accurate AFR.
My problem lies with the desired and reported airflow values. At the desired idle RPM in Park or Neutral, the car idles properly around 8g/s of airflow. Following the RAFPN table, the PCM thinks the car wants ~2g/s (after ST/LTITs). The values I use in B4307 seem irrelevant, as the PCM constantly reports to want some absurdly low amount of air. Regardless of where the values in B4307, the car still will swing right to 8g/s. The airflow values I am given to use from the trims are nonsensical, and constantly want extreme adjustment. I am right around 80 IAC steps at hot idle.
Now, when I shift into gear, the IAC immediately opens almost all of the way (sometimes it goes to the max of 310 steps). This is highly annoying, as the car has to sit still for some period of time to "learn" back downwards. If it moves before it's learned completely, the idle flares back up to ~1400rpm. The RAFIG process results in the same odd values. The car thinks it wants >22g/s in gear, but idles at the proper rpm (once it learns down) around 11g/s. No matter what values I put in B4307, the car wants more air. If I put what it wants (22g/s), it shows IACDES_B to want 26g/s. As soon as a gear is selected, the desired airflow jumps up, as do the reported airflow values (although they do not go as high). Even after learning back down to the proper rpm, IACDES_B shows some apparently ridiculous number (the learned values also have no effect in B4307).
The trims always point to some nonsensical value. I can't get the desired airflow values (IACDES_B) to match the values in B4307, and I can't get the idle trims to be reasonable.
I have played with the "Idle" section extensively, with no avail. Clearly, the desired airflow values are no reasonable.
Things I know:
The IAC motor is not sticking, nor do I have vacuum issues. I am not confusing units. The fueling at idle is (relatively) normal. B4307 seems to have no effect on IACDES_B. I have not found any PID that seems to add the values to IACDES_B on top of the B4307 (such as throttle cracker/follower, startup friction, etc.).
What tables/parameters effect IACDES_B (or: how can I fix this)? My current tune is attached, and I can gather a log of any PIDs suggested. I've described the behavior shown in my various scans.