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Thread: Tuning AFR part throttle help

  1. #1
    Tuner in Training
    Join Date
    Oct 2018

    Tuning AFR part throttle help

    hey guys, just a quick question about tuning to your AFR both MAF and VE

    it seams no matter how much I try my idle and low throttle never get corrected. Most of the graph I can get close to +/-5 but my idle is always off. I?m tuning based off my wideband with my fuel trims turned off. When i turn the trims back on they get me close but than my AFR jumps around and my fuel trims are never steady. Also if I try tuning off my fuel trims and not my wideband I have the same issue. I am running a big cam and switched to a LS3 MAF. My curves are good and my WOT is almost perfect for my commanded AFR

    my question is would the size of my camshaft throw off my readings at idle and low throttle on both MAF and VE tuning?

    Anything I can do to dial in better?

  2. #2
    How far off are the idle trims? Is it an E38 processor?

    You might post your tune and a datalog to let us take a look.

  3. #3
    Advanced Tuner
    Join Date
    Feb 2015
    Perth, Australia
    yes camshaft, depending on size can make idle tuning a real challenge.

    given the excessive overlap I often find the STFT at idle to be constantly trying to remove fuel due to false data.

    I've seen people take the data as gospel and rape the VE and MAF curve to get good fuel trims at idle but in fact when checked with a wideband its lean as hell.

    E38 LS3 with cam will physically idle at 17:1 AFR with enough air. the STFT will be spot on but its super lean. that can make transition off idle and into part throttle very poor.

    with a decent cam I would suggest disabling all trims and going full open loop. use wideband only data to tune your VE and MAF tables independently of each other in entirety. then enable dynamic or blended fueling and clean them up.

    research end of injection timing on here. read up on the suggestions with a cam to maintain a clean idle. it will likely help.

    personally I do nearly everything in SD. so I either set up so it will only idle in open loop or do a full open loop calibration. otherwise I just accept that the narrow bands will remove a percentage of fuel at idle from incorrect data and edit the VE table to that with the -STFT active the idle AFR is still OK. but cold idle in that case will be a bit rich until it enters closed loop

  4. #4
    Tuner Camaro6's Avatar
    Join Date
    Jun 2018
    Send me the stock tune and modified tune with a log and I'll take a look. What cam and overall setup you have going?

    LS3 with TSP F35 Stage 4 cam, PRC heads, etc was no problem to idle at 800rpm steady, good fueling, and put down some stout numbers on the dyno with the right tweaks. It's my nephews car and he can daily drive it no problem, heck his Mom drives it even without any issue.

    Orange 14 1LE Camaro on TSP FB and Instagram is my tuning. He sent in a rev up video from his phone to TSP a little while back and I posted the video idling and a pull on the dyno in the comments. 465tq/518hp You'll see the AEM Wideband running also during the idle portion. He wanted it to chop good, so it's set 1.04ish Lambda at idle in closed loop.
    2018 Camaro SS, LT4 Fuel System, LT4 S/C