Daveo91
07-10-2019, 09:37 AM
Starting another thread on one of the most significant lingering tuning issues on my vortec/TBI 383 for my '91 3/4T 4wd Burb with 4L80e and 7060 PCM. This thread is essentially the continuation of another (here (http://www.gearhead-efi.com/Fuel-Injection/showthread.php?7518-Tuning-help-needed-91-TBI-383-w-Vortec-heads)) but I thought I'd start fresh since I've done some things since then and have started zeroing in (I hope) on the problem.
Lingering issue: weird and annoying cyclic surge on deceleration. Instead of RPM decreasing linearly during smooth decel, it oscillates with a 200-300 rpm amplitude and approx 1 sec period.
What I've done: installed AEM WBO2 system. '7060 does not have provisions for incorporating WB data with its datastream, but I can see it pegging lean during decel in cycles that match those described above.
I've also gotten better with tunerPro datalogging and I have exported a recent datalog to an Excel file that has a number of decel events included. Then I grabbed the data from just one of those events and pasted it into another sheet in the same file. Then I graphed RPM vs Time on one vertical axis and Speed vs time on the other vertical axis. The graph shows speed decreasing smoothly (it's in small steps due to TP only reporting speed to nearest MPH) while RPM looks like a decreasing sine wave.
I tried to attach my Excel to this post, but the site wouldn't let me. Here's a link (https://drive.google.com/file/d/1MCbEtbXk71M7ttssGbc67yxpUZLkBd2b/view?usp=sharing) to it shared on Google Drive. If someone was willing to look on at my log, but doesn't want to click the link, PM me and I'll get it to you any way you want.
What I'm asking for: help with figuring out what is causing the ECM to pull fuel in a cyclic fashion during decel. In the export I've included everything that I thought would remotely matter in trying to figure this out, but if I've missed something let me know and I'll gladly redo the export. My only clue right now is the parameter called "AIR Management" My burb did not come stock with an AIR pump and it certainly does not have one now, but I'm wondering if this could be doing something to cause problems. It does seem to trigger ON and OFF seemingly at random, but it also seems to doing it at other times besides just decel. Maybe something else completely, I don't know. Just know I'm at my wits end to try to get the decel surging eliminating. There are a couple other lingering problems but I'll tackle those next.
One other clue, I can eliminate the surge completely by running open loop.
Any thoughts? Anyone?
Lingering issue: weird and annoying cyclic surge on deceleration. Instead of RPM decreasing linearly during smooth decel, it oscillates with a 200-300 rpm amplitude and approx 1 sec period.
What I've done: installed AEM WBO2 system. '7060 does not have provisions for incorporating WB data with its datastream, but I can see it pegging lean during decel in cycles that match those described above.
I've also gotten better with tunerPro datalogging and I have exported a recent datalog to an Excel file that has a number of decel events included. Then I grabbed the data from just one of those events and pasted it into another sheet in the same file. Then I graphed RPM vs Time on one vertical axis and Speed vs time on the other vertical axis. The graph shows speed decreasing smoothly (it's in small steps due to TP only reporting speed to nearest MPH) while RPM looks like a decreasing sine wave.
I tried to attach my Excel to this post, but the site wouldn't let me. Here's a link (https://drive.google.com/file/d/1MCbEtbXk71M7ttssGbc67yxpUZLkBd2b/view?usp=sharing) to it shared on Google Drive. If someone was willing to look on at my log, but doesn't want to click the link, PM me and I'll get it to you any way you want.
What I'm asking for: help with figuring out what is causing the ECM to pull fuel in a cyclic fashion during decel. In the export I've included everything that I thought would remotely matter in trying to figure this out, but if I've missed something let me know and I'll gladly redo the export. My only clue right now is the parameter called "AIR Management" My burb did not come stock with an AIR pump and it certainly does not have one now, but I'm wondering if this could be doing something to cause problems. It does seem to trigger ON and OFF seemingly at random, but it also seems to doing it at other times besides just decel. Maybe something else completely, I don't know. Just know I'm at my wits end to try to get the decel surging eliminating. There are a couple other lingering problems but I'll tackle those next.
One other clue, I can eliminate the surge completely by running open loop.
Any thoughts? Anyone?