Tightening Fueling - Questions - O2 Proportional vs Transient Impact Factor - DSteck?

[BigDaddyCool]

So basically I wideband tuned my maf, and I've decided to go narrowband tuning my VE for the time being to get it 'closer' as I find the wideband running on one bank vs narrowband by 4 sensors is more accurate but I have a few questions.

1. On the STFT it swings like 10+ to -10 say.... despite eg. averaging -2 or 0 etc.... and LTFT in the same spots may only average a small negative.

2. Startup running on just VE when I first start the car I notice the trims are pretty lean like +10 and it stutters a fair bit for about 5-10 seconds.

So what I'm sort of wanting to know is, should I be looking at O2 proportional or transient maybe for solving some more spike lean conditions sometimes on quick throttle and do you have any idea on the startup issue of the car.

Do I need to adjust 'open loop' tables maybe to add fueling when closed loop isn't running.

It's a bit of a speil this I know, I've managed to bring trims inline fairly well but I'd like to solve the massive swing I see of an average say of +10 to -10..... despite how it averages out.

It may be my VE is still off...... Doesn't ultimately explain the startup stutter, maf is disabled etc......

I figured I could bump proportional up a fair bit and drop ve back down and that may solve this but still..... I haven't messed with transient gear which I think is probably where I need to look at ....... because I dont know virtually any way of seeing how those tables impact fueling in the particular spots on quick throttle movements etc.

Maybe you could chime in here DSteck?.

PS. I'm currently running off the stock timing table, I half though of adding timing in the richer spots to help close the gap on the fueling issue..... ? I have changed headers, intake and exhaust so,

[ttz06vette]

In terms of the lean spots you are experiencing, transient modifications worked me. I used my scans to pinpoint the IVT/MAP area where the lean spot was occurring and increased the transient gain(gas) table in this specific area. Then I added to the impact table at the lower airflow cells and brought transient in quicker by lowering the "delay" to 15.
I think my problem was driven by heat soak as I am running a sheetmetal intake. As the manifold heated up I believe fuel was evaporating quicker than these tables accounted for. By adding transient fuel at low airflow rates and in specific Map/IVT points I was able to compensate. May not be the most elegant way but my lean/flat spot is gone.

[carlrx7]

how many miles on your o2's?

[BigDaddyCool]

My O2's have done about 105,000km's (65000 miles)? .....

As for the transients, yes I'd setup some histograms to check the trims against the different IVT's vs MAP etc to compare at different temperatures. My biggest concern at present is when I start the car however...... I still have the maf hooked up but setup all the fail settings etc to make sure it disables but when I start the car it sort of splutters and what not until closed loop kicks in....

Is that due to failing the maf and taking a second? ..... My point here is if I decide to stay/run completely mafless and just want to leave the maf there will it do this everytime.... I haven't logged it with a wideband yet, judging on narrowband's o2 voltages on startup i'd say it's running much richer then requested on startup.... but even so doesn't explain the weird stumble/splutter. Doesn't do it when maf is enabled, only when it's set to fail the maf.... and run ve only.

Idea's? I'll post up a tune and scan if you wish to see if I have something oddly out of place when I get home. All looks fine.... has me stumped, obviously fueling is out somewhere on startup and without the maf to correct it, somethings going a bit silly.