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Thread: Difference in STFT's..

  1. #1
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    Difference in STFT's..

    I asked in an old thread but no response so I will try a new one.

    After my recent build I noticed a 10 -15 % difference in the STFT. I checked everything possible and can't find anything wrong. I pulled the plugs and noticed that 2 on bank 2 looked a bit leaner than the rest. I added a little fuel to those cylinders using the "gain vs cylinder" table and the trims are much closer like that. Is there any reason not to run it this way? I am thinking there is a slight variation in fuel from either th blower runners, cam, heads, or for whatever reason, and this seems to even things out.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  2. #2
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    As long as you have no introduced any knock, I cannot see a reason why not.

    On a side note, I see you are using the 2Bar Map as well, how did you populate the Main VE tables?
    2008 Corvette C6 A6
    E force 599HP kit, 3.25 pulley
    ZR1 Cam, ATI Balancer
    160 stat, Dewitts Radiator
    LG 1 7/8 Superpros, delete cats, xpipe
    Century Built 6l80e, Ext. Transmission Cooler
    3200 Yank
    2.73 rear

  3. #3
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    Quote Originally Posted by mrgillies View Post
    As long as you have no introduced any knock, I cannot see a reason why not.

    On a side note, I see you are using the 2Bar Map as well, how did you populate the Main VE tables?


    I cannot see any reason why not either, I just cant find anything on anyone using these tables.

    I havent tuned the VE tables yet for the new build. Originally i started them by taking the tables out of the tune with Bluecat, and copied them into the new os.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  4. #4
    Senior Tuner DSteck's Avatar
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    I don't know why this works, but I had a discussion with a guy who was tuning his Kenne Bell 2010 Camaro himself. It had huge left to right discrepancies in fuel trims (wideband verified). He got around it by delaying EOIT. You might give that a shot. Like I said, I have no idea why that worked for him.

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  5. #5
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    Quote Originally Posted by DSteck View Post
    I don't know why this works, but I had a discussion with a guy who was tuning his Kenne Bell 2010 Camaro himself. It had huge left to right discrepancies in fuel trims (wideband verified). He got around it by delaying EOIT. You might give that a shot. Like I said, I have no idea why that worked for him.
    I would try it. Could you elaborate a bit on which table exactly he changed.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  6. #6
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    Dave,

    Some advice if you do not mind. I came across your spreadsheet for the EOI tables. Very nice I must say.
    For some reason my "normal rpm" table is all 0's. Should I just change the idle area using the spreadsheet, or should I fill the whole table. It is the idle that I am working on now and I am not sure if filling the higher rpms will effect my WOT setting if I change them.

    Thanks for any input on this. Your input is always appreciated.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  7. #7
    Senior Tuner DSteck's Avatar
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    Experiment. As I said, that spreadsheet is a visual aid and comes with no advice on how to set it. Lol.

    DSX Tuning - Authorized HP Tuners Dealer
    http://www.dsxtuning.com
    http://www.facebook.com/dsx.tuning
    Just say no to bull s***.
    IF YOU WANT HELP, POST A FILE!

  8. #8
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    Quote Originally Posted by DSteck View Post
    Experiment. As I said, that spreadsheet is a visual aid and comes with no advice on how to set it. Lol.
    Thanks for the spreadsheet just the same.

    visual aids for the tuning impaired are always appreciated.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  9. #9
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    Ok...I'm stumped. I have checked and tried everything I can think of. I tuned the maf with afr error and its very good, but one stft trim is perfect and the other is off as much as 15%. Anyone have any suggestions of what I can check
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  10. #10
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    swap o2's side to side

  11. #11
    Senior Tuner DSteck's Avatar
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    Roll a hand grenade under the car.

  12. #12
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    Quote Originally Posted by DSteck View Post
    Roll a hand grenade under the car.
    Thanks !! You should write a book with those tuning tips.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  13. #13
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    I have given up! O2's checked out good. Spent the aft looking for vacuum leaks every way possible including using a smoke machine. Can't find any leak.
    what I did tonight is tune the maf using an average of STFT bank 1 and bank 2. After checking with AFR error its a perfect lambda 1, give or take a percent. The banks still differ by 10-15% but at least I know the AFR is good.
    The only thing I can think of is something in the build. Heads, porting, runners, or ???.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  14. #14
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    Has anything changed mechanically with the O2 on the side that has the discrepancy? Placement or did you extend the wires? I don't know if or how it all gets effected but it may be that something has skewed the signals going back to the ecm.
    15 C7Z M7

  15. #15
    Senior Tuner DSteck's Avatar
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    This is just something typical in a lot of PD blowers. GM went to great length to make sure the LSA/LS9 setups get even distribution. You may just be stuck.

    DSX Tuning - Authorized HP Tuners Dealer
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  16. #16
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    Everything on the car has changed exept the O2's. Same sensors, same wiring, same headers.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  17. #17
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    Quote Originally Posted by DSteck View Post
    This is just something typical in a lot of PD blowers. GM went to great length to make sure the LSA/LS9 setups get even distribution. You may just be stuck.
    I could understand that. What puzzles me is I was running the same blower before, without this issue. It a different short block, cam, and some work on the heads, but same blower.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  18. #18
    Senior Tuner DSteck's Avatar
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    The cam may just cause some weird reversion at certain operating conditions that doesn't jive with the blower.

    DSX Tuning - Authorized HP Tuners Dealer
    http://www.dsxtuning.com
    http://www.facebook.com/dsx.tuning
    Just say no to bull s***.
    IF YOU WANT HELP, POST A FILE!

  19. #19
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    Quote Originally Posted by DSteck View Post
    The cam may just cause some weird reversion at certain operating conditions that doesn't jive with the blower.
    Yeah. I have checked everything possible so have to believe its something like that. Its only at idle and just above. After about 1200 rpm the trims equalize as normal.
    2007 Corvette C6 Vert. A6
    LME LS402, Pat G custom cam, ATI 10% OD Damper
    Circle D triple disc 2600, 3.42 Diff
    YSI, 3.0 pulley, ID 1000's
    Alky Control Meth,
    ARH 1 7/8 headers,
    1009 RWHP @ 7000, 817 RWT @ 6000

  20. #20
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    Quote Originally Posted by realcanuk View Post
    I have given up! O2's checked out good. Spent the aft looking for vacuum leaks every way possible including using a smoke machine. Can't find any leak.
    what I did tonight is tune the maf using an average of STFT bank 1 and bank 2. After checking with AFR error its a perfect lambda 1, give or take a percent. The banks still differ by 10-15% but at least I know the AFR is good.
    The only thing I can think of is something in the build. Heads, porting, runners, or ???.
    If you have an air leak before or just after the O2's you will notice the STFT's being really erratic and not smooth curves at lower RPM's (idle - 1000 rpm), they get better (smoother) when more air flow is achieved.

    Ask me how I know.... LG Superpros have a slip on connector that passes air if not adjusted prior to install
    2008 Corvette C6 A6
    E force 599HP kit, 3.25 pulley
    ZR1 Cam, ATI Balancer
    160 stat, Dewitts Radiator
    LG 1 7/8 Superpros, delete cats, xpipe
    Century Built 6l80e, Ext. Transmission Cooler
    3200 Yank
    2.73 rear