Lean on cold starts, occasional lean on hot starts, AFR error, chasing my tail

[FD3S]

04 GTO LS1, ported 243 heads, 227/230 .613 .608 Comp cam, longtube headers into a single 3.5", free-air calibrated NGK AFX after the y-pipe, transform function based on logging raw voltages during it's startup routine, OTR intake with a MAF/IAT setup, saxonpc honeycomb, Ford red top 30# injectors, Supra TT fuel pump, Corvette regulator/filter (58PSI falling to 55PSI when warm).

I feel like the tune is pretty close, but could use a little help to finish it up.

The car seems to go lean on cold starts and the occasional hot start. I thought maybe the cold was from the OLFA table being 1.00 in some of the colder ECT ranges, but I added a bit today and it didn't seem to make a difference. Should I add more here or could there be something else? I guess the reason I'm confused is because, as mentioned, it does this on hot starts as well and then will taper off to normal after a bit. My waythere.hpl log shows the lean start issue, and some cruising in MAF/VE blended mode. (Note: the fuel trims are from me adjusting my O2 switchpoints. With the switchpoints at 451mv, the car would be 14.57 (as commanded) in VE, but would drop down to ~14.1x-14.3x when running closed loop, with STFT within a few percent. I was adjusting switchpoints to see if I could get the car to trim at 14.57 in closed loop.)

For my VE table, I've noticed that I can putt around, get everything in line, make a few minor adjustments, and then drive it again a few minutes later with totally skewed results. I pulled over, got gas, and tossed the car in VE mode. This is the ve.hpl log, and aside from the idle cells, most of it looks decent. So, I halved the idle cells only (these were off from because of a change yesterday, but that's another story), and drove it around again. The ve_idle_adjust log is a hot start lean example. It pegged lean until I started driving it, and was still hovering in the 15.x range. Eventually, toward the end of the log, it evens back out. I don't understand this.

I made no other changes to VE, and loaded a MAF only tune. Did this, numbers were between 1-8%, so I multiplied by half, did it again, multiplied by half again. It was starting to rain so I decided against any more for the time being.

I copied the new MAF data into my blended tune, adjusted the switchpoints to 415mv just to see how it would trim, and drove home (wayhome.hpl). Slight lean start, but tapered off quickly. AFR is stable, but "rich". My fuel trims look decent, AFR error is a bit off, but the car drives fine.

So, questions -

Not sure where to begin with the hot start issue. I could keep adding to OLFA for cold, but I don't understand the hot start lean unless it's IAT heat soak or something?

Not sure what to do about the AFR error in blended mode, and why I can't get it to trim at 14.57 like I can in SD and/or MAF-only mode. I realize that it's only a few percent, but it seems like everyone else can actually get their tune to trim to whatever they're commanding, and I don't know why mine is off.

I realize that is sort of a wall of text, but I've been chasing my tail with this stuff and I'd love to get it dialed in before winter I've tried searching a bunch (which helped with lots of other parts of the tune), but can't seem to get this ironed out.

waythere.hpl
ve.hpl
ve_idle_adjust.hpl
wayhome.hpl
base_rtt.hpt

[FD3S]

Additional files

base_rtt_ve.hpt
after_tune_drive_test.Graphs.xml
after_tune_test_drive.Charts.xml
after_tune_test_drive.Channels.xml

[dermotw]

The IAT table is ok, right? IAT is standard?

[FD3S]

Doing a compare to a stock 04 GTO file, I can find no differences in any of my IAT tables vs stock.

[FD3S]

I *may* have had the logs posted at .69 + 9, due to my incompetence (I thought I changed the transform function in all of my saved channel configs, but when I checked this earlier it was .69 + 9.) Either way, the numbers were still a bit off, but the transform function should be dead nuts accurate otherwise. My channel set up for VE tuning has the correct transform function.

Cold start, it went lean again, but this time it didn't peg it lean.

So, coldstart.hpl shows the lean cold start condition and drive.hpl shows the cruising around richness. I set the switchpoints back to 451mv for testing purposes.

startup_cold.hpl
drive.hpl

[HackAbuse]

On my 05 GTO, I implemented the use of IAT vs IFR to cancel out STFT bias during cold start and heatsoak. Worked really well for my application

[FD3S]

Do you mean initial adder vs IAT? If not, maybe the table you're talking about is a gen IV table? I guess the question, even if I have the table you mention, is why would this need done? I guess I'm trying to understand what's different about my setup that's causing the issues I'm seeing.

[FD3S]

Still seeing the lean start issue, and can't find anything in the tune causing it. I put the car into open loop idle, and it's still doing it on hot and cold starts.

From today, I started the car at 187*, and it went lean. AFR commanded was correct, WB was pegged. It tapered down to 15.50 before leaning back out to ~16. I tapped the throttle and it looked normal, went slightly lean, then slightly rich as the revs fell, went back to ~15.50, and then tapered back down to ~14.6.

I haven't had time to try and tweak anything else related to the blended AFR issue.

[FD3S]

I was trying to track down the cause of the low base running airflow numbers, so I bought a regular oil cap to replace my breather filter oil cap. Cap on, fresh air line ran from the TB to the passenger valve cover, valley port ran to intake manifold, same numbers. I bought a new set of intake manifold gaskets, just to be 100%. I replaced them this morning even though mine looked fine. Still have low airflow numbers. Nothing looks out of place visually. I even replaced the MAP rubber seal with another one I had lying around just because the one on mine had a very small crack in it.

If the car ran normally, I guess I wouldn't be concerned about these numbers, but with the lean starts, the AFR in CL being off, and some other issues I'll get into in a minute, I can't help but think it's all somewhat related.

Driving home, the car was hunting for idle. I assume this is related to my low RAF numbers, but who knows at this point. Car randomly started commanding 15.88 AFR, then 13.52, in log 1. O2s flatlined.

Edit : Fixed the deleted bit. It was something stupid I overlooked. No longer an issue. The low RAF, the off AFR numbers, and the odd commanded AFR are still a thing though.

[FD3S]

A question about low RAF and idle surging. When I got the car, the RAF was twice as high as it is now (and, realistically, probably closer to where it's supposed to be). What would be the downside to using artificially high RAF numbers, and letting STIT deal with the changes? Will LTIT eventually try to correct itself making the high numbers moot? I can't imagine where else might have a vac leak, so I'm not sure why the numbers are so low.

[dermotw]

Related to the idle, the logs look like just the various idle parameters need a tweak to stop/reduce the idle surges, unfortunately it seems like every car combination is different in that area, mine was a sod to get close, I spent weeks... The spark cycles higher/lower at idle than most say is "good", and as you say, your idle RAF appears too low, it would more likely be around 6-8 (just imho, I'm no expert). Don't see why the o2's halted switching 'tho, unless you have some sensor issue or? -In the middle of that drive-from log, they went dead lean, then dead rich, then "resumed normal service"... ? errr?? Also at that time the fuel trims didn't! (trim, that is..).

[FD3S]

Found this thread for my shifting commanded AFR. I changed my rear O2s from "No error reported" to "No MIL Light" and I'll see what happens, but this seems like the fix for that. One thing at a time

Edit : didn't see your post before I posted my last update.

As for the RAF, I do believe that's causing the surging, but really I'm just unsure of how effective just setting the RAF numbers 2-3 g/s higher would be, as they may LTIT down anyway.

[dermotw]

Hmm, mine still has the rear o2's fitted/wired, although no cats or anything else emissions-related. Mine are set to No Error Reported and no MIL... COT disabled, EGR disabled, blah. I'll have to watch if mine ever does this, I haven't seen it, but it might!

The RAF, it'll be more than just the numbers there, you'd likely need to tweak some others, in my case, the ones below, and more I don't even recall it all... But I have a light flywheel as well. Don't take my values as gospel, just to show how different they can be...

Capture.JPG

Capture2.JPG

Something else that @got@ me was that when you force the car to e.g. OL and do MAF/VE tuning, it also disabled the evap purge. Then, when you set everything back on, after a while it goes rich on idle, because it dumps loads of built-up tank pressure into the manifold....

EDIT: You have lean cruise, I don't, that may be why I never saw this..???