Idle BLM

[BLG355]

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]

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]

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