Results 1 to 15 of 15

Thread: STFT negative but LTFT positive? LTFT goes to 1.00 when I touch the throttle

  1. #1
    Advanced Tuner
    Join Date
    Aug 2015
    Posts
    230

    STFT negative but LTFT positive? LTFT goes to 1.00 when I touch the throttle

    So I'm trying to dial my ID1000 injectors in and on first start I was getting 1.00 LTFT and consistent ~0.8 STFT indicating it was rich at idle.

    I went around the block, restarted car and LTFT started kicking in reading ~1.21 fairly consistently at idle. If I get the rpm to ~3000rpm in neutral LTFT drops to 1.00 instantly and STFT go back to ~0.8. It seems to disable LTFT as soon as I touch the throttle, why is this?

    Why does the STFT and LTFT seem to pull the fuel in opposite directions? I'm confident the engine is running rich due to injector settings in my old tune. As I have ID1000 I would assume neutral at 3k would still use low slope and hence I'm a bit confused.

    Forgive the basic questions I am still learning

  2. #2
    Advanced Tuner
    Join Date
    Dec 2005
    Posts
    222
    What year vehicle? If pre-2011 (pre-Copperhead) then this is correct. In the narrow-band control vehicles STFT < 1.0 and LTFT > 1.0 are both adding fuel while STFT > 1.0 and LTFT < 1.0 are removing fuel.
    Jeff Chambers, Owner
    CRT Performance, LLC
    349 Cleveland Road
    Norwalk, OH 44857
    Ph: 419-668-4151
    Fx: 419-668-4643

    Performance Parts, Service and Dyno Tuning Specialists

  3. #3
    Advanced Tuner
    Join Date
    Aug 2015
    Posts
    230
    2007 Australian ford falcon turbo Spanish oak ecu

    Ok that makes way more sense, very odd they chose to do it though?

  4. #4
    Advanced Tuner
    Join Date
    Dec 2005
    Posts
    222
    As far as the 3000rpm blip, you probably just don't have enough time in that area for the LTFT to have learned. Put some road miles on it, trying to hit as many driving points as possible with enough time in each for the LTFT to stabilize (e.g. steady state). Create a histogram of your LTFT and make your fueling corrections from those.
    Jeff Chambers, Owner
    CRT Performance, LLC
    349 Cleveland Road
    Norwalk, OH 44857
    Ph: 419-668-4151
    Fx: 419-668-4643

    Performance Parts, Service and Dyno Tuning Specialists

  5. #5
    Advanced Tuner AKDMB's Avatar
    Join Date
    Sep 2014
    Location
    NC
    Posts
    344
    My car was doing this exact same thing the other day at idle. LTFT's were around 3% and STFT's were at -3%. It does this to some extent during other driving conditions too. The MAF curve is within 1/2% to 3% lean, you can barely tell a difference between it and the stock trace. I'm assuming with more miles it will stop opposing itself so much.

  6. #6
    Advanced Tuner
    Join Date
    Jun 2008
    Location
    Tyler/Longview, TX area
    Posts
    746
    I had my MAF within 2% error last week. This week I'm fine tuning the spark tables and have only 1 MP active at a time. I really wasn't paying any attention to the MAF because I thought it was all good, but today I noticed the LTFTs were up to 4% off and my STFT had 2 cells show 11% error(2 separate logs). Those same 2 cells on LTFT table are less than 1% error. I think I read somewhere that different VCT timing will effect the MAF. I'm thinking because I'm locked into 1 MP(OP) It has changed my MAF curve. I will turn them all back on tomorrow and do another log to see if the 2 11% error cells are still there.
    One thing that doesn't make sense to me is if the LTFTs are reset every time I load a tune, how are they so far off from STFTs on the same log?

  7. #7
    Advanced Tuner
    Join Date
    Dec 2005
    Posts
    222
    Remember that the STFT are heavily influenced by other factors such as transient fueling, rapid load changes, decel, ambient temp changes, etc. Use the LTFT to adjust the MAF and then let the STFT do what they will. If your long terms, after a significant period of learning, are within 3-4% then you're in good shape.
    Jeff Chambers, Owner
    CRT Performance, LLC
    349 Cleveland Road
    Norwalk, OH 44857
    Ph: 419-668-4151
    Fx: 419-668-4643

    Performance Parts, Service and Dyno Tuning Specialists

  8. #8
    Advanced Tuner
    Join Date
    Aug 2015
    Posts
    230
    So the poster that said ltft and stft work in opposite direction directions for narrowband vehicles is wrong? What if the correct answer??

    Also what do people man by ltft for a certain cell? I thought there was only one ltft value of are you saying there is one for each tps/lambda cell?

  9. #9
    Advanced Tuner
    Join Date
    Dec 2005
    Posts
    222
    Quote Originally Posted by rolls View Post
    So the poster that said ltft and stft work in opposite direction directions for narrowband vehicles is wrong? What if the correct answer??

    Also what do people man by ltft for a certain cell? I thought there was only one ltft value of are you saying there is one for each tps/lambda cell?

    ????
    Jeff Chambers, Owner
    CRT Performance, LLC
    349 Cleveland Road
    Norwalk, OH 44857
    Ph: 419-668-4151
    Fx: 419-668-4643

    Performance Parts, Service and Dyno Tuning Specialists

  10. #10
    Advanced Tuner
    Join Date
    Jun 2008
    Location
    Tyler/Longview, TX area
    Posts
    746
    Quote Originally Posted by jchambers View Post
    Remember that the STFT are heavily influenced by other factors such as transient fueling, rapid load changes, decel, ambient temp changes, etc. Use the LTFT to adjust the MAF and then let the STFT do what they will. If your long terms, after a significant period of learning, are within 3-4% then you're in good shape.
    Does making only 1 MP active change the way the MAF works/learns?

  11. #11
    Advanced Tuner
    Join Date
    Dec 2005
    Posts
    222
    Yes and no. The logic is that the final delivered conditions are the weighted average of the active points. So if you have purposely limited it to the OP all of the time, then OP would be 100% of the weighted average and all other points would have a contribution of 0%. This may indeed have an effect since cam position, timing, etc. are based on the single sample set from OP. If you run the car in OP all the time, great...but as soon as you reactivate other points you'd likely see some error/variation due to their contributions.

    For example:

    f(x) = a*P1+b*P2+......+p*P16 where a+b+.....+p=1.0
    Last edited by jchambers; 10-16-2015 at 11:28 AM.
    Jeff Chambers, Owner
    CRT Performance, LLC
    349 Cleveland Road
    Norwalk, OH 44857
    Ph: 419-668-4151
    Fx: 419-668-4643

    Performance Parts, Service and Dyno Tuning Specialists

  12. #12
    Advanced Tuner
    Join Date
    Jun 2008
    Location
    Tyler/Longview, TX area
    Posts
    746
    Quote Originally Posted by jchambers View Post
    Yes and no. The logic is that the final delivered conditions are the weighted average of the active points. So if you have purposely limited it to the OP all of the time, then OP would be 100% of the weighted average and all other points would have a contribution of 0%. This may indeed have an effect since cam position, timing, etc. are based on the single sample set from OP. If you run the car in OP all the time, great...but as soon as you reactivate other points you'd likely see some error/variation due to their contributions.

    For example:

    f(x) = a*P1+b*P2+......+p*P16 where a+b+.....+p=1.0
    Thanks Jeff. I will leave my MAF as is until I turn the other MPs back on.

  13. #13
    Advanced Tuner
    Join Date
    Aug 2015
    Posts
    230
    Quote Originally Posted by jchambers View Post
    ????
    Sorry I replied to the wrong thread
    See here. I believe our cars are quite different as they don't have a maf and the terminology is different that you use.

    I just want to make sure what you said is true for the STFT and LTFT in the Australian ford ecus.

    http://www.hptuners.com/forum/showth...932#post401932
    Last edited by rolls; 10-16-2015 at 05:10 PM.

  14. #14
    Advanced Tuner
    Join Date
    Dec 2005
    Posts
    222
    i cant comment on the aussie ecus. It would be simple enough to determine though. screw your VE in one direction (rich or lean) then observe the response of the corrections.
    Jeff Chambers, Owner
    CRT Performance, LLC
    349 Cleveland Road
    Norwalk, OH 44857
    Ph: 419-668-4151
    Fx: 419-668-4643

    Performance Parts, Service and Dyno Tuning Specialists

  15. #15
    Advanced Tuner Auto-Hentzschel's Avatar
    Join Date
    Sep 2015
    Location
    Schleid, Germany
    Posts
    341
    [QUOTE=
    For example:

    f(x) = a*P1+b*P2+......+p*P16 where a+b+.....+p=1.0[/QUOTE]

    Hello, can anyone explain me this formula please!