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Thread: My gas mileage is horrid!

  1. #1

    My gas mileage is horrid!

    My last 2 tanks i got 11 mpg on my cammed full bolt on ls1.

    But basically, I got my VE and MAF right on the spot with a wideband. Im commanding 12.8 richened to 12.6 through pe. I havent been driving that crazy.

    It seems like there are quite a few people getting better than this with similar setups. I am going to give closed loop + reenabling dfco a shot.

    Car is completely tuned up as well.
    Last edited by pHEnomIC; 05-27-2007 at 06:05 PM.

    My SOM T/A's FQuick!
    2002 T/A: Torquer V3, Full Boltons, Suspension, M6, Lots of misc things.
    My Z/28's Cardomain (13.9 @ 101.1)
    1997 Z/28: A4, Some boltons, Lots of misc things.

  2. #2
    HP Tuners Support
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    Bill@HPTuners's Avatar
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    have you had DFCO enabled?
    It doesn't have to be perfect, it just needs to be done in two weeks...

    A wise man once said "google it"

  3. #3
    Dfco was disabled the last two tanks.

    My SOM T/A's FQuick!
    2002 T/A: Torquer V3, Full Boltons, Suspension, M6, Lots of misc things.
    My Z/28's Cardomain (13.9 @ 101.1)
    1997 Z/28: A4, Some boltons, Lots of misc things.

  4. #4
    Senior Tuner S2H's Avatar
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    I would suspect that your wideband is off...
    I've never seen less than 23ish with just a bolt on car

    DFCO doesnt improve gas mileage all that much...

    please post your tune..
    I've tuned a number of bolt on only cars and can see if something seems amiss with it
    -Scott -

  5. #5
    Well my car is cammed too but still, mileage should be better than 11.

    I can't seem to find my latest maf scan file, i think i deleted it but after a couple corrections i was getting very low a/f error with the maf enabled. Car drives awesome, any suggestions are welcome.

    My SOM T/A's FQuick!
    2002 T/A: Torquer V3, Full Boltons, Suspension, M6, Lots of misc things.
    My Z/28's Cardomain (13.9 @ 101.1)
    1997 Z/28: A4, Some boltons, Lots of misc things.

  6. #6
    Senior Tuner S2H's Avatar
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    Quote Originally Posted by pHEnomIC
    Well my car is cammed too but still, mileage should be better than 11.

    I can't seem to find my latest maf scan file, i think i deleted it but after a couple corrections i was getting very low a/f error with the maf enabled. Car drives awesome, any suggestions are welcome.
    well...you VE table is Whacked...and its probably the main cause for your eating too much gas....
    I grabbed a stock and a cammed file and you have way too much airflowq going on from 3200-5200 in your lower map cells
    and you have a wierd high spot in the low map low rpm cells as well..so you are probably just dumping in fuel when you shouldnt be
    teh entire lower side of rpm in your VE table looks like hammered shit...which will cause some crappy fueling...
    it shouldnt look like a mountain range with all kinds of peaks and valleys..
    its ok to have some ups and downs...but they shouldnt be as drastic as yours is...

    without a recent tune file and a log that is current I cant really say 100% on this...but I'll bet its the reason for your issues
    -Scott -

  7. #7
    Ok how does this sound? I am going to do a free air calibration on the wideband and disable the maf again, go through and do some VE corrections and then reenable the maf and correct for that again. Will that do the trick?

    My SOM T/A's FQuick!
    2002 T/A: Torquer V3, Full Boltons, Suspension, M6, Lots of misc things.
    My Z/28's Cardomain (13.9 @ 101.1)
    1997 Z/28: A4, Some boltons, Lots of misc things.

  8. #8
    If my VE was way off though, wouldn't the car run like absolute junk especially in Open loop? I am a bit surprised when i heard you say it is way off. I spent a lot of time doing corrections and eventually it settled in with consistently very little a/f error (<2% on average). The car runs amazingly, i can't believe how good it is running. I do have a 231/234 .644/.598 111 lsa cam btw.

    My SOM T/A's FQuick!
    2002 T/A: Torquer V3, Full Boltons, Suspension, M6, Lots of misc things.
    My Z/28's Cardomain (13.9 @ 101.1)
    1997 Z/28: A4, Some boltons, Lots of misc things.

  9. #9
    Senior Tuner S2H's Avatar
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    I cant say that its way off..but to me it looks whacked....
    just needs to be smoothed out and to me it looks like too much fuel in teh 3200-5200 low MAP areas...
    I've got biger cams with less fuel there..and wondering if thats part(most likely not all) of your issue


    you could be down in the 12's at part throttle and it would still run great...
    -Scott -

  10. #10
    Tuning Addict WS6FirebirdTA00's Avatar
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    I agree, the VE is screwed up pretty bad. When you use the data, you cant just use it blindly, if things dont flow well you may have some bad data in that cell. Thats why I take min 25 counts. The timing looks jacked up too, you dont want random dips like that.

    I would check the WB for sure. If you are running CL now, I would suspect shitty o2s, people never check them and then think the tune is bad.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  11. #11
    Aside from the funky VE table, you said this is an SD Tune - Is the MAF unplugged?? If no, it looks to me as though the MAF is still being used and if yes may explain some fuelling anomolies - otherwise as per the gurus' advice.

  12. #12
    Ok i did another ve and maf tuning session, please check it out now:

    Free air calibrated my wideband
    Disabled & unplugged maf,
    smoothed out my ve table by hand and wrote a calibration
    let it warm up
    went for about a half hour drive varying conditions to hit many cells,
    multiplied by corrections and hand smoothed just a couple points.
    Reenabled my maf, plugged it in
    wrote calibration
    Went for a half hour drive back home varying conditions again,
    multiplied my maf table by a/f error and hand smoothed a few points and wrote tune. (here is my final tune attached)
    I am also including my logs of the ve and maf run

    Any other problems you see with my tune?

    btw: pids:
    Wb A/F ([PID.2811]/.625)+10
    A/F error 100*((([PID.2811]/.625)+10) -[SENS.121])/[SENS.121]

    My SOM T/A's FQuick!
    2002 T/A: Torquer V3, Full Boltons, Suspension, M6, Lots of misc things.
    My Z/28's Cardomain (13.9 @ 101.1)
    1997 Z/28: A4, Some boltons, Lots of misc things.

  13. #13
    Tuning Addict WS6FirebirdTA00's Avatar
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    You wonder why you were drinking fuel.....

    You were 20% rich at high MAP and as rpm went up it got worse in the VE. I knew those numbers looked too high.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB