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Thread: Questions about driveability tuning

  1. #1
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47

    Questions about driveability tuning

    Car basics - '04 LS1, MAF with saxonpc honeycomb, ported 243 heads, Comp 227/230 .613/.608 114 LSA cam, Ford red top injectors, Supra TT pump, Corvette regulator (58PSI cold, falling to 55PSI warm,) 1 3/4" longtubes into a 3.5" single exhaust. NGK AFX wideband (calibrated twice - it's about halfway back on the exhaust, after the y-pipe, around 70" off the engine. No cats.) and HPT Pro V3.0.8.

    When I bought the car, it would start and drive fine, but idle/cruise seemed rich and WOT seemed lean. I picked up HPT to try and correct this.

    So, a few things (wall of text incoming) -

    I first tuned VE and MAF based on AFR error from the wideband. I used DStecks' recommendation of .7096 and 9.102 to try to get the software to read "correct" stoich numbers based on a 14.68 stoich input. I got everything to line up pretty well, and then not long after I started throwing codes for lean banks 1+2. I checked my LTFT, and they were something like +15 (maybe more, I don't have that log in front of me.) I decided to re-tune using STFT instead. Doing it this way, I was able to get STFT in line, turned LTFT back on and those are no more than 3% off right now, so it seems a lot better.

    I realize that 70" is pretty far back and out of NGK's recommended range. (I'd like to move this at some point, to either ~37" from engine on the passenger bank, or ~50" back on the driver's bank. That's the closest I can get based on clearance.) However, I'm curious as to what the real affects here are. In a closed system (no leaks), I understand that the reading will be slightly delayed, but does anyone have data showing that the numbers get skewed? I'm not saying it doesn't happen, I'm mostly just trying to understand why my wideband reads 14.0-14.4 most of the time at idle, with some swings +/- those numbers, while the STFT is spot on. The narrowbands obviously like the setup, but the wideband is "off". I'm concerned that this might also affect readings at WOT, although I'm not seeing significant knock or anything.

    On that note, would having longtubes play into my narrowband readings? When I looked at this the first time, both O2 switchpoint tables were set to 451 across the board. I noticed that stock is different, and looking at some sample tunes from others with longtubes I noticed that no one else seems to have these flatlined like that. How would I know/adjust to get this in proper order?

    Lastly (for now ), I'm interesting in base running airflow/throttle cracker/throttle follower setup. Because most histograms, config files, etc are for older versions, I don't seem to be able to view them in a meaningful way and I'm not sure what values I need to add to create my own histograms for these. I just wanted to verify that my base airflow is indeed correct, but I'm also having the following issue - when you start the car cold and drive around, everything acts very normally. If you turn the car off hot, and turn it back on a minute later and start driving, the idle will hang at ~1700RPM until you drop under the disable speed. After driving around for a bit this will stop and idle normally while moving, but I'd like to correct it. I'm not sure what I should be checking/comparing here.

    Basically, I'm trying to understand the changes and how things get affected, but it's been a little difficult to search because of the OS version file differences, so I thought I'd ask. Any help is appreciated.
    Last edited by FD3S; 07-16-2016 at 09:13 AM.