Idle BLM

**Roadknee** · 06-09-2015

$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** · 06-09-2015

Originally Posted by Rocko350

Yes. The values in the 800 rpm line. Set those to the cells around them in the 30,40, and 50 kpa lines. Look at your over speed and under speed tables. Are they stock? How does the vehicle react during the transiotns from closed hrottle in gear to c/t in park. Any surge or stall?

Chris

It is pretty smooth. Sometimes it will surge a little and then settle out after going drive to neutral. Going into gear it always seems good.

BLG

**BLG355** · 06-09-2015

Originally Posted by 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.

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** · 06-24-2015

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** · 06-24-2015

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** · 06-25-2015

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** · 06-25-2015

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** · 06-25-2015

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

**Roadknee** · 06-26-2015

I took a look at your log. I really don't see any surge and it's definitely better than what 355chev is experiencing with his bigger cam. I don't know how much more I can help.

I wish I was smart enough to read code and understand how those fuel trim parameters are used to influence pulse width. I have a general idea, but to advance my understanding will take a lot more trial and error. Another reason to get the new engine finished and in my truck.

You've done a great job with your VE table. I've never seen one with as many cells that close to 128.

I noticed the initial advance in your BIN is set to 1.4 degrees. Is this where you have initial advance set with the timing light? It's important these two match because the ECM subtracts the initial advance from the values in the main timing tables.

I think your engine could benefit from more light throttle low RPM advance. I recommend setting the 2,000 rpm 30, 35 and 40 MAP cells to 40 degrees and blend into the surrounding cells. If you have any mild surge in these areas more advance might help.

**BLG355** · 06-28-2015

I ran a two logs today to see how it looked. I did notice one thing, during open loop it stuttered pretty bad off idle, looking at the log I see it appeared to be very lean. But the confusing part is on the second log I ran once it was all warmed up, it is removing fuel from all the cells. This will lean out he open loop startup even more correct?

Overall it feels really good, and it may not be surging I am feeling. But I noticed in the log, steady throttle and speed and timing, the rpms change. I'll attach a screen shot. It may be totally unrelated. Can changing the fuel trim parameters change the BLM's this much? I noticed they are all much lower. I changed the STOICH AFR from 14.7 to 14.1 too, which I though would go the other way, perhaps this could be why the BLMs are all lower now?
Attachment 9187

On the timing, I did have it right between 1 and 2 degrees but I did just get it back to zero and fix the initial advance in the BIN. I've been slowly modifying the timing table. I like to make a change and drive it a few days to see how it feels overall. I've been slowly adding more in that range, I'll keep going and see how it works.

Once warmed up, it feels good with the exception of very light throttle I think I am feeling pulsing of sorts below 2,000rpms but it's hard to tell with the aggressive tires. I've been driving it a lot more lately and I'm sure 99.99% of people that would drive it and never notice it.

BLG

**Roadknee** · 06-29-2015

Well, I'm pleased those fuel trim parameters seem to be working. It took a lot of trial and error with 355chev to get there.

With the warmer weather we're having, perhaps the lean condition in open loop was due to the coolant temp being warmer, and the ecm was in a leaner part of the open loop afr vs temp vs vacuum table. The AFR the ECM was targeting during the lean condition was in the 15.3 to 16 range. You could try setting all the values above 14.5 to 14.5 in that table.

It's normal to see up to 50 rpm change in the log even when the true rpm is steady. It's just noise.

In all the work with 355chev, changing fuel trim parameters never changed BLM's significantly. Your BLM's went down because you reduced the stoich AFR from 14.7 to 14.1, about a 4% change. I imagine your BLM's were about 4% lower too, and you would need to reduce the VE table values by about 4% to bring them back in line. Or just put the stoich AFR back to 14.7.

**BLG355** · 06-30-2015

I will give that a shot. I was wondering if perhaps the large throttle body could be causing perhaps what I am feeling? The throttle is extremely sensitive and I was starting to wonder if at such light throttle with all the air coming in it isn't flowing consistent? I am seriously considering going back to the 350 one because I will probably hardly every go over 5000rpm anyways. I will have to drive it some more to see if I can get used to the touchy throttle. In the past year I only put 3000 miles on it...I will have to start driving it more.

BLG

**BLG355** · 07-03-2015

Originally Posted by Roadknee

I think your engine could benefit from more light throttle low RPM advance. I recommend setting the 2,000 rpm 30, 35 and 40 MAP cells to 40 degrees and blend into the surrounding cells. If you have any mild surge in these areas more advance might help.

Is the upper rpm stuff ok at 40 too? Like 2000+ rpms in the 30,35 and 40 all to 40 degrees? I attached pics of what I did. I have surging about the 2000rpm though. less than 50kpa and 2000-2500 rpm I get some. So I think I will try changing the tables a little bit and see how it responds. Anyone ever go over 40 degrees in any of those cells?

BLG

**Roadknee** · 07-03-2015

I've run as high as 50 degrees in those cells, but that's usually for a larger cam with more overlap. The maximum advance the ECU will add is just under 42 degrees. If you want to add more, you'll need to bump up the initial timing. Personally, I like your spark map and would leave it where it is.

I don't see surging in the log. Not saying it's not there; just I don't see it. Try reducing the Upper Limit for Slow Filtered O2 (scalar) from 903 mV to 850 mV and give it a try. You can also multiply the values in the Proportional Duration Offset vs Airflow table by 0.5. I'd try these changes one at a time and together to see if they help any.

**BLG355** · 07-03-2015

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