Idle BLM

[Roadknee]

$0D has specific proportional gain values for idle in Scalars. I think that table if for off-idle only. If your engine has larger capacity injectors and larger cam, and experiences a surge during O2 swings, reducing the values in that table where the surge is occurring can help get rid of it.

[BLG355]

$0D has specific proportional gain values for idle in Scalars. I think that table if for off-idle only. If your engine has larger capacity injectors and larger cam, and experiences a surge during O2 swings, reducing the values in that table where the surge is occurring can help get rid of it.

I am trying to figure out where this surge I have is coming from. It seems anything below 2000 rpm at light throttle it surges. Cruising down the highway with the TCC I notice it pretty good. If I get the the throttle it goes away, it seems to be the worst 50KPA-20KPA. I tried lowing timing to get rid of it but it made no difference. It was around 34-36 in the higher vacuum lower rpm ranges and I slowly lowered it down to the mid twenties with the same results. I was assuming it was from O2 latency but no matter what I try there I cannot clear the surging. My last resort is to move the O2 sensor to the header and out of the Y-pipe but I was hoping to be able to get it out with the tune. Perhaps I will give this a try.

BLG

[BLG355]

I'm still messing with this. I read some from this thread http://www.gearhead-efi.com/Fuel-Inj...2-problem(long) and tried some of these settings with horrible results, I wanted to share. I was amazed I could actually see the surging on the log it was so bad. I thought the sub 2000rpm surging was bad before, this is really bad. So I'm thinking the o2 settings may be ok. I copied all the settings from the posted bin into mine, and I noticed the cross counts were going like crazy...perhaps too fast and causing the surging? I just can't seems to get anything I plug into this thing to work.

This is one hard thing to get straightened out. I really don't want to move the O2 from the stock location, but I guess I am going to have to and give it a try. It's really going to suck if I move it and it isn't any better. It seems the smoothest with the BIN I attached. I lowered the prop gain settings, I'm not 100 percent sure it did too much, it did throw the BLMs out of whack which I am working on getting those straightened out again. over all it isn't bad, but it definitely isn't right. what sucks is I had zero surging before the headers, after the headers install it started. Anyone have any other ideas or perhaps see something I am overlooking or didn't do?

Thanks.

BLG

[Roadknee]

The surge is caused by the O2 swings. It's interesting to note that installing headers on my stock engine did not create a surge. But I have helped 355Chev tune most of the surge out of his. He runs a 10:1 Vortec headed 355 with a bigger cam than yours and the Flowtech version of your headers with the O2 sensor in the stock location.

I've loaded the fuel trim parameters from his current BIN into yours (with slightly lower O2 thresholds) and attached below. They are a lot different than what you are running. Although I can't make any promises, I'm optimistic you'll see some improvement.

[BLG355]

I tried this bin on my way home from work and ran a log with it. It feels pretty good overall but I will run another log out on the highway and such to see how it feels. In the log you can still see some pulsing that looks like it goes in coordination with the o2 sensor. I think it's getting closer though. Is it the frequency of the o2 swings or is it more of a balancing act or both? what would be the first thing to try changing?

BLG

[Roadknee]

I'm on the road so can't view the log. Try bumping up the values in the rich O2 voltage vs airflow table by 100

[brian617]

Some good info here on closed loop fuel control, about halfway down under Process Control. There are many more pages of good info also on this site.

http://www.masterenginetuner.com/efi...peration2.html