Idle BLM

**Roadknee** · 07-05-2015

Originally Posted by BLG355

I'll give that a try. I hope to have time this weekend to run a few logs and make some small changes to see if I can eliminate or at least move the surging again to perhaps figured out what I am changing to remove it from certain spots and hopefully eliminate all together. When it does it now, it almost feels like a manual transmission when you go on and off the throttle. About every second or so I can feel on-off-on-off-on feeling. The lower rpm stuff seems to be really good now, but the 2000-2500rpm when gently cruising seems to really buck now. Bucking is a better word for it lol!. Thanks again.

BLG

I took another look and saw the surge or bucking your refer to. I think reducing the proportional gains some more in those areas is also worth a try. See attached. This, together with reducing the upper limit for low filtered O2 should do it. Try these before reducing the prop duration offset vs airflow table.

**brian617** · 07-06-2015

Out of curiosity Roadknee, what is happening when you reduce the values in that table? Lower values = ? Higher values = ?

**Roadknee** · 07-07-2015

Originally Posted by brian617

Out of curiosity Roadknee, what is happening when you reduce the values in that table? Lower values = ? Higher values = ?

The fuel trim parameters together influence the ecm base pulse width calculation. When the O2 is rich, the ECM reduces the BPW to swing it lean. When the O2 is lean the ECM increases the BPW to swing it rich. Reducing the proportional gains reduces the amount the ECM alters the BPW and increasing the proportional gains increases the amount the ECM alters the BPW to swing the O2.

**BLG355** · 07-07-2015

I lowered the upper limit for low filtered O2 from .903 to .851, I will give this a try and see how it works. I will also try the prop gain as well(a few days later), I'm curious how it will respond even if it feels ok after changing the upper limit for low filtered O2. I'm curious, I noticed in several different similar tunes that the o2 mv is different. Is there a reason these get changed? Sometimes they are all the same, sometimes they are like these where 0 airflow is higher mv and sometimes its opposite.

Attachment 9250

I changed my bin and I'll swap the chips tomorrow and run it for a few days. it is definitely pretty good. But it seems like it gets better in one spot and falls off somewhere else. I need to stop changing so many things at once! lol.

Thanks again for all your help. Everyone has been extremely helpful and I appreciate it all.

BLG

**brian617** · 07-07-2015

Originally Posted by Roadknee

The fuel trim parameters together influence the ecm base pulse width calculation. When the O2 is rich, the ECM reduces the BPW to swing it lean. When the O2 is lean the ECM increases the BPW to swing it rich. Reducing the proportional gains reduces the amount the ECM alters the BPW and increasing the proportional gains increases the amount the ECM alters the BPW to swing the O2.

Reducing the number would decrease the amount of PW correction to switch from rich to lean or lean to rich correct? I can see where having a substantial increase of fuel pressure over stock like Barry and I are running, would make for a larger correction than needed.

**BLG355** · 07-12-2015

I ran a few days after changing the upper limit for low filtered O2 from .903 to .851. I still have some surging so I am currently changing the prop gain to how roadknee recommended. it's definitely going better and feels very close, I just have to keep trying these little things until I find the sweet spot. Thanks again for everyone's input and help.

BLG

**Roadknee** · 07-12-2015

Thanks for checking back in, Barry. If the prop gains don't do it, we'll probably try richening the O2 voltage threshold tables. I'd like to see a standing start 0-60 mph WOT datalog on a straight flat road if you get a change. Ideally with decent traction.

**BLG355** · 07-15-2015

Originally Posted by Roadknee

I'd like to see a standing start 0-60 mph WOT datalog on a straight flat road if you get a change. Ideally with decent traction.

Still hasn't happened!

I thought I found a decent spot tonight, the traction was way better but it was slightly uphill. I spent last Sunday at the race track, I am thinking about taking the truck there this Sunday. If I do I will log every run. But here is my log for tonight I ran to check the BLM's and feel the surge difference, which I usually feel when filling in all the hard to fill cells out on the highway. I am also messing around with the timing at an idle as well which I will post a question or two about later. Here is the log from tonight with much less wheel spin, and a tad uphill. I think it pulled pretty hard the whole time, it felt good.

BLG

**Roadknee** · 07-15-2015

Originally Posted by BLG355

Still hasn't happened!

I thought I found a decent spot tonight, the traction was way better but it was slightly uphill. I spent last Sunday at the race track, I am thinking about taking the truck there this Sunday. If I do I will log every run. But here is my log for tonight I ran to check the BLM's and feel the surge difference, which I usually feel when filling in all the hard to fill cells out on the highway. I am also messing around with the timing at an idle as well which I will post a question or two about later. Here is the log from tonight with much less wheel spin, and a tad uphill. I think it pulled pretty hard the whole time, it felt good.

BLG

Overall I think that log looks really good. You ran 0-60 at 7.5 seconds a tad uphill... damn good for a heavy truck. Your converter flashes to 2,800 which probably helps. It's interesting that the BLM's in the areas where you reduced the proportional gains are a little low now. I hope you make it to the track. About all I'd suggest is to add some TPS AE in the bottom cells of the table. When you mashed the throttle the O2 went lean in the log.