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Thread: maf dropping flow in the middle of a pull

  1. #1
    Tuner in Training
    Join Date
    May 2020
    Posts
    13

    maf dropping flow in the middle of a pull

    Hello friends,
    I have a 07 GT500, with a kenne bell 2.8 with the twin 75mm throttle body. The car is on the 2.75" pulley and should see 21psi roughly. For fuel it is a return system with 1000cc deatchwerk injectors. I was having issues rolling into W.O.T and made adjustments to the effective area table and predicted area tables.
    Since then, it seems to have improved, but i notice an odd point in the middle of the pull where the maf seems to time out. Trims are safe up to that point, in most cases they are pulling fuel...
    I have attached the log file and if you look right at 1:23, it is reading 84.38lb of air and drops 1 second later to 1.29lb.....
    I could not feel anything and it seemed to be smooth so i was paying attention to the road looking straight ahead. Seems to be occurring at 5200rpm. I have my timing down very low right thankfully, but this has me scared. I noticed my throttle value is still not quite 82%. I would love any and all input on the calibration I have thus far And what you think might be causing this issue.

    I have loaded my calibration file and the log. Thank you all for your help. effective area redo with driver demand and dashpot adjusted wot successful.hptwot 6000rpm maf drop.hpl

  2. #2
    Tuner in Training
    Join Date
    May 2020
    Posts
    13
    surely somebody has encountered this?

  3. #3
    There seems to be 2 camps, the first says don’t dork with TB data if you have good published values, the other says you need to adjust them at times. I left my Whipple TB data stock because that’s what folks like Banish suggest, but the Whipple data seems overly simplistic.

    Now I have now idea how a TB data change could effect the MAF but it sound ps like it did, are you sure the issues you were having were in the TB data? I assume if you revert TB data the issue goes away? Does load stay consistent, or drop?

  4. #4
    I looked through the log, not the tune. First it would be a good idea to log load, fuel source, torque source and spark source. That data would help diagnose the issue. Secondly, looking at the log I'm wondering if it's an issue with the scanner itself. If your MAF lbs dropped down that low you would go extremely lean. Narrow band volts are indicating that fuel didn't leaning out. They are reading the same before and after the drop in MAF. If MAF lbs really dropped out like that at WOT on a boosted car it would nose over at the least.
    Paul
    Modern Muscle Motorsports
    www.modernmusclemotorsports.com
    Custom tuning using Diablosport, SCT, HP Tuners, Tuner Cat, FAST & Holley
    Dynojet 224x mobile dyno


  5. #5
    Tuner in Training
    Join Date
    May 2020
    Posts
    13
    Thank you friends, for the responses!

    Superman07, I am completly open to the idea that the changes i made could have been the cause.... I didnt log load. my previous versions wouldnt even allow me to get up into the higher revs or throttle.

    ModerMuscle- Paul, Thank you so much for that info, I will be adding that to my future logs. Just judging by the log, there was a slight dip in rpm at 5200... but at the time, it was moving quick and i felt nothing. it felt very smooth. I will delete and download the scanner again tonight. see if anything changes.

    Thank you both for your help!