Suddenly pig rich

[Jim Blackwood]

Good call. Not real sure what exactly that PID was, it was the only MAP channel labeled as 2 bar. However once I activated the SAE and voltage channels I got a better picture of what was going on. I have it reading correctly now and I have a 2 bar sensor on the engine with a genuine Delco one on the way. I will test it again once that gets here and probably use a pressure rig for the boost part of the range.

The only way I can make sense of the sequence of failure is that possibly there is a failure mode in the Chinese 2 bar sensor that makes it revert to 1 bar? That would explain the failure and I can think of nothing else that would, because I was able to tune the engine and then I wasn't. The sensor I removed is outputting correctly as a 1 bar, though it may be a bit over sensitive on the low end. Probably should go in the round bin, in fact I just did that. It's been more trouble than it was worth.

Looks like I'm back to regular tuning anyway. Concentrating on startup, warmup, and idle for now. That and learning how to properly set up the traces for the AFR. I'm using the Innovate MTX-AL with the EGR input on C1-55 so it's not just plug-n-play, and so far I've struggled with it. But I hope with experience I'll get better at setting up the scanner. That would need to be another thread though.

Jim

[Jim Blackwood]

Hey guys. Thought you'd want to know the outcome. To make it short, a self inflicted wound of course. Be careful and methodical when turning off error messages. Turn off the wrong ones and (so I've heard) the ECU won't exit closed loop or something, which makes everything act very strange if you are tuning in speed density. So I was able to track down a tune from way back on the 9th of June and that one worked fine. Started good, idled down, and no surge. I'm down to 800rpm on the idle now, something this engine has never done before. And I'm pretty sure it can go slower, but with an aluminum flywheel it probably shouldn't.

Anyway, I got my scanner pretty well sorted out at last and have been running some histograms to edit the VE table (copy/paste, now below 3.0 and dividing by 2) and my AFR is getting pretty close to commanded afr. This is after warmup and at very light throttle settings. And this brings up a question. Probably a stupid one, but if I don't ask I won't learn so here goes. I'm sure I'm not the first.

About that commanded afr. That's pretty close to 14.7, actually a bit richer than that. I get that PE takes care of heavier throttle applications and I really haven't been playing with that yet. But if the commanded afr is trying to hit 14.7 and the engine needs more fuel because it's starting to take on a load, and the PE hasn't kicked in yet, what happens? I mean, at light throttle I can see it all working rather nicely and I suppose the EQ Ratio Subtractor settings take care of lean cruise once those are set up (mine are all zeros), but I'm a little worried about adding power without more fuel.

Any recommendations?

Also I'm still predominantly rich, black soot in the tailpipes, under 12 when I hit the gas so I should probably lean out the PE once I figure out how but presently the car is running quite good.

Jim

[brian617]

About that commanded afr. That's pretty close to 14.7, actually a bit richer than that. I get that PE takes care of heavier throttle applications and I really haven't been playing with that yet. But if the commanded afr is trying to hit 14.7 and the engine needs more fuel because it's starting to take on a load, and the PE hasn't kicked in yet, what happens? I mean, at light throttle I can see it all working rather nicely and I suppose the EQ Ratio Subtractor settings take care of lean cruise once those are set up (mine are all zeros), but I'm a little worried about adding power without more fuel.

Jim

If I understand what you're asking, you wont be able to tune LOAD areas of the VE table until you actually introduce load via a dyno or the street. In either case there is no reason why you cant just sneak up on those areas of the map with out damage to the engine. You'll have to have the VE table dialed before you can use the PE table to command a proper AFR.

[Jim Blackwood]

OK thanks. So do I need to zero out the PE tables to work on the rest of the VE table?

Jim

[brian617]

You could, or set the PE delay timer to some un-reasonable value. They're generally set pretty high anyway.

[Jim Blackwood]

OK I'll do that.

What I'm seeing for AFR Commanded ranges between 13.2 and 13.7 which seems rich to me. My measured AFR is running 12.2 to 13.5 mostly, with an offset generally under 1.5 and this is at very light throttle application, generally around 20-30 kPa.

What would be the best way to bring these numbers up closer to stoich?

Jim

[Jim Blackwood]

Slowly creeping up on it. It's got this thing right now where it idles down to 800 but then when I start driving it the idle stays up around 1300. I need to sort out what is causing that. I think it could be the IAC since it is open more (~30 vs 20) but I don't know why. I seem to be closing in on stoich, though commanded remains about 14.0, I guess I can pad the numbers for commanded AFR by maybe .7 to 1.0 in the formula to get the correction once it has settled down a bit more if it's needed. No real hurry now. It's about close enough now to be able to make a fairly accurate comparison between the trace and the AFR meter.

Starting is pretty good but warmup seems to be richer than it should be so that will be next. Transitions seem pretty good although initial off idle is a lot less crisp than it should be, makes me want to blip the throttle too much and that shouldn't be necessary at all. Should be adjustments for that too.

You guys are the best btw, in case I haven't said that lately.

jim