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Thread: The final truth: LTFT's and WOT

  1. #21
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    Quote Originally Posted by Z06SUPERCHARGED View Post
    If you just disable them then you dont have to worry about them.,,,pretty simple procedure.
    Agree, and that would be easy...but it doesn't answer the question! :-)

    (offtopic)

    But since I have a black 2003 Z06 with FFS fuel system...and with A&A Vortech T-trim...and with bunch of other upgrades from Andy...and the car exported from Northern California (to be exact, from a guy named Mr. Smith @ Novato, Ca), I could actually do what you're suggesting. And yes, I'm also running 2 bar Speed Density COS as probably you as well...



    You might actually recognize this location:



    Small world, isn't it? :-)

    (end of offtopic)

  2. #22
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    So in other words... back to the original question....
    Last edited by Z06SUPERCHARGED; 03-17-2010 at 06:01 PM.
    16 psi on E85

  3. #23
    ^^^ I noticed that with the LTFTS enabled my car learns/trims to 11.7 where the PE shows 1.25 (this is a stock ls1 pcm) so 14.63/1.25 is 11.7.... I have since turned the LTFTS off because they trim towards this commanded PE after a few WOT runs. It appears that because of my intake setup(now bolt ons) the car will run 12.7-12.9AFR with the LTFTs DISabled and the stock 11.7 commanded PE table..... thought that was interesting.... dont know what to take from it other than.... I guess the intake setup supplies more air....

    I thought it was easier just to turn the LTFTs off than mess with the PE table.

    yes I am a major class NEWB

  4. #24
    Senior Tuner S2H's Avatar
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    at part throttle if your wideband reads more than a couple of 10ths off...then your wideband is wrong
    car should trim at 14.6/14.7ish... if you see 14.4 average..no big deal... if you see 11.7? then you have a problem with your wideband

    your stock narrowbands can only trim at 14.7 and will always be accurate to that.. they will never trim more than a couple of 10ths out of whack...
    -Scott -

  5. #25
    Quote Originally Posted by soundengineer View Post
    at part throttle if your wideband reads more than a couple of 10ths off...then your wideband is wrong
    car should trim at 14.6/14.7ish... if you see 14.4 average..no big deal... if you see 11.7? then you have a problem with your wideband

    your stock narrowbands can only trim at 14.7 and will always be accurate to that.. they will never trim more than a couple of 10ths out of whack...


    THIS IS AT WOT - 11.7
    the car cruises at stoich.

  6. #26
    Advanced Tuner 69lt1bird's Avatar
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    If you are commanding 11.7 at WOT in the PE table and you are getting 12.7-12.9 then you have issues in the tune. Sure the intake may have increased the air going in so that means more fuel is now needed.
    You never said if you actually tuned the VE or MAF tables with the wideband.
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  7. #27
    Senior Tuner S2H's Avatar
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    Quote Originally Posted by Dskeet6 View Post
    ^^^ I noticed that with the LTFTS enabled my car learns/trims to 11.7 where the PE shows 1.25 (this is a stock ls1 pcm) so 14.63/1.25 is 11.7.... I have since turned the LTFTS off because they trim towards this commanded PE after a few WOT runs. It appears that because of my intake setup(now bolt ons) the car will run 12.7-12.9AFR with the LTFTs DISabled and the stock 11.7 commanded PE table..... thought that was interesting.... dont know what to take from it other than.... I guess the intake setup supplies more air....

    I thought it was easier just to turn the LTFTs off than mess with the PE table.

    yes I am a major class NEWB

    the way you describe this is that you were using trims and getting 11.7 on your wideband

    becuase of how this post was worded it doesnt sound like you were doing WOT...

    now knowing that...

    for WOT - you dont use trims...your car doesnt Trim at WOT...
    if it is trimming at WOT it is only because your narrowbands saw a lean condition just before WOT and the car will "Self preserve" by adding a little more fuel at WOT.

    if this is the case...then turn off all your trims in the VCM controls and reset all the fuel trims as well...
    then you can go about tuning WOT without having to worry about trims and you can re-enable trims at your leisure without having to stop the car

    once you are happy with WOT, go back and fix your part throttle trims by making changes in the VE.

    you CAN do part throttle and WOT at the same time using a wideband with all trims off..
    -Scott -

  8. #28
    Quote Originally Posted by soundengineer View Post
    the way you describe this is that you were using trims and getting 11.7 on your wideband

    becuase of how this post was worded it doesnt sound like you were doing WOT...

    now knowing that...

    for WOT - you dont use trims...your car doesnt Trim at WOT...
    if it is trimming at WOT it is only because your narrowbands saw a lean condition just before WOT and the car will "Self preserve" by adding a little more fuel at WOT.

    if this is the case...then turn off all your trims in the VCM controls and reset all the fuel trims as well...
    then you can go about tuning WOT without having to worry about trims and you can re-enable trims at your leisure without having to stop the car

    once you are happy with WOT, go back and fix your part throttle trims by making changes in the VE.

    you CAN do part throttle and WOT at the same time using a wideband with all trims off..

    ^^^ sorry I meant to say without ANY tuning at ALL other than disabling and enabling the LTFTS this is how my car behaves. Again I am not using trims for anything... just noting that the car itself must be trimming towards 11.7 since it starts off 12.9afr at WOT and learns towards 11.7....

    to this day no one is able to explain how this is happening other than saying my tune is off..... yes I understand that tuning the VE table via wideband feedback will correct my tune for the AFR I want by adding fuel, but for whatever reason my car runs right around 12.9 with LTFTs turned off and when they are ENABLED, the car then sees 11.7 commanded on the PE table(1.25). SO in ORDER witht he LTFTS enabled this is what happens

    when I clear the cars trims it runs 12.9AFR for a few WOT runs and then sees 11.7AFR... this is what I meant to say. This is not bothersome to me as the car runs great with the LTFTS off. I have no time to tune the VE table and I am in no rush to do so.... yes my tune is off but the car runs FINE..... so I just meant to let everyone know how my car acts with the LTFTs enabled.

    apologies,

    Supernewb
    Last edited by Dskeet6; 03-19-2010 at 12:33 AM.

  9. #29
    ^^^^ my car is stoich everywhere at part throttle with some trimming via STFTs..... I assume it is coincidence that the car runs high 12 AFRS at WOT with the modifications I have made and a stock VE table.
    Last edited by Dskeet6; 03-19-2010 at 12:31 AM.

  10. #30
    Senior Tuner S2H's Avatar
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    Quote Originally Posted by Dskeet6 View Post
    ^^^^ my car is stoich everywhere at part throttle with some trimming via STFTs..... I assume it is coincidence that the car runs high 12 AFRS at WOT with the modifications I have made and a stock VE table.

    also a quick question....then I have your answer

    are you still using the MAF at all? is it enabled or disabled?



    now your answer

    when your trims are enabled....they are most likely trimming because of a lean condition(positive trims)
    because of this...WOT follows triming that happens just before you go into PE
    so your car is trimming because of lean and carrying over to WOT...
    this is normal

    what it means is that you need to retune your VE/MAF so that the trims are slightly negative so that it doesnt carry over into WOT/PE mode

    our cars always add fuel if trims are positive, but never take away fuel if trims are negative.



    2nd issue....

    just because you tune in open loop with trims off...doesnt mean your trims and your wideband line up

    only way to check is to have both going at the same time...
    which means you need 2 bungs in a similar location.
    get a second bung welded into one of your exhaust primaries..its usually about $25-$40 at any reputable exhaust shop.
    then you can check one against the other...

    I can guarantee that more than likely your wideband and narrowband o2's wont show exactly the same thing if you are having the issues you stated above by the methods you have used to tune part throttle....because if they did, you wouldnt be having this trimming issue.
    at 14.7AFR 4% = .588afr
    so if your trims are 4% you will see14.1ish at cruise or 15.2ish at cruise on your wideband



    also...the reason I asked about the MAF...at WOT...above 4k your car goes to 100% MAF if its still working....
    and below 4k the car will use a blend of VE and MAF when it is still enabled
    which means your problem could be in the MAF if its not diabled/removed
    Last edited by S2H; 03-19-2010 at 02:47 AM.
    -Scott -

  11. #31
    Tuning Addict WS6FirebirdTA00's Avatar
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    Most + trims I see happen in OL are due to poor transient fueling, where it may spike lean. The o2s see this trim for it and it locks on. Setting up your fuel trims cells can also help some of this. Sometimes you still get stuck with crappy LTFT data locking in for WOT.
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  12. #32
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    I've skimmed this thread and I don't know that the OP's original question has been answered. The reason that LTFTs affect WOT fueling is because it uses the LTFT of whatever fuel trim cell you were in just before you entered PE. So while no fuel trim data is collected in PE, the LTFT of the fuel trim cell you left closed loop is tacked onto the PE if it is positive. So if you are commanding 1.13 (13:1) and the fuel trim cell you entered PE in is +5 then you are actually commanding 1.13x5%=1.187 (12.4:1). If the LTFT is negative it does nothing.
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  13. #33
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    Thank you. No more questions from me.

  14. #34
    Quote Originally Posted by soundengineer View Post
    also a quick question....then I have your answer

    are you still using the MAF at all? is it enabled or disabled?



    now your answer

    when your trims are enabled....they are most likely trimming because of a lean condition(positive trims)
    because of this...WOT follows triming that happens just before you go into PE
    so your car is trimming because of lean and carrying over to WOT...
    this is normal

    what it means is that you need to retune your VE/MAF so that the trims are slightly negative so that it doesnt carry over into WOT/PE mode

    our cars always add fuel if trims are positive, but never take away fuel if trims are negative.



    2nd issue....

    just because you tune in open loop with trims off...doesnt mean your trims and your wideband line up

    only way to check is to have both going at the same time...
    which means you need 2 bungs in a similar location.
    get a second bung welded into one of your exhaust primaries..its usually about $25-$40 at any reputable exhaust shop.
    then you can check one against the other...

    I can guarantee that more than likely your wideband and narrowband o2's wont show exactly the same thing if you are having the issues you stated above by the methods you have used to tune part throttle....because if they did, you wouldnt be having this trimming issue.
    at 14.7AFR 4% = .588afr
    so if your trims are 4% you will see14.1ish at cruise or 15.2ish at cruise on your wideband



    also...the reason I asked about the MAF...at WOT...above 4k your car goes to 100% MAF if its still working....
    and below 4k the car will use a blend of VE and MAF when it is still enabled
    which means your problem could be in the MAF if its not diabled/removed
    Yes the MAF is still enabled. I attempted to tune the MAF a few months ago and saw that the greater the cell counts I had, the MAF started towards - percentages I believe(or whatever was desired). So >100 cell counts showed the MAF was fine.... which was strange because I have intake mods upstream of the sensor. Is this normal and what # of cell counts should I rely on???

    This is great information.... thank you. I had no idea that LTFTS carried over into PE if they were positive trimmed. This makes sense because my LTFTs were positive by more than 10%. I just thought it was strange that the WOT fuel(PE) with the LTFTs was what the car was commanding(14.63/1.25 = 11.7) after a few wot runs.

    Ok so I need to tune:

    1.) the MAF via stft?
    2.) then the VE table so LTFTs are slightly positive across the board.
    3.) then PE table...

    Now if trims are + and I make them negative through VE tuning but the wideband then shows its not cruising at 14.6-14.7 then there lies a problem with o2's age possibly??
    Last edited by Dskeet6; 03-19-2010 at 12:15 PM.

  15. #35
    Quote Originally Posted by 69lt1bird View Post
    If you are commanding 11.7 at WOT in the PE table and you are getting 12.7-12.9 then you have issues in the tune. Sure the intake may have increased the air going in so that means more fuel is now needed.
    You never said if you actually tuned the VE or MAF tables with the wideband.

    this is happening on STOCK VE and MAF tables.

    I have not tuned anything yet other than DFCO and turning LTFTs off

  16. #36
    Advanced Tuner 69lt1bird's Avatar
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    You need to tune the MAF with the wideband (AFR error %), tune the VE table with the wideband (AFR error %). Its really that cut and dry.

    Have the LTFT turned off while doing the tuning. Don't worry about the trims until you have the other two dialed in correctly. If you do those right the trims will fall in line.

    The guide in my signature works pretty good and explains some of the naming and what it does. Try that and follow the instructions. Others have had success with it, give that a try.
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  17. #37
    Quote Originally Posted by 69lt1bird View Post
    You need to tune the MAF with the wideband (AFR error %), tune the VE table with the wideband (AFR error %). Its really that cut and dry.

    Have the LTFT turned off while doing the tuning. Don't worry about the trims until you have the other two dialed in correctly. If you do those right the trims will fall in line.

    The guide in my signature works pretty good and explains some of the naming and what it does. Try that and follow the instructions. Others have had success with it, give that a try.

    so I just drove a little and tuned the VE for cruise using the LTFTs where stfts are around 0 - this is starting to look good. For WOT I calculated the PE to 12.8 across the board and 12.7 where peak cam is..... and made the VE fat above 85MAP so it would compensate for my mods. It looks good but I am still slightly lean and already have a hump of 106% around 5400. I calculated the PE and Im changing the VE until my wideband reads the commanded PE at WOT. cruise cells look good on ltfts

    how am I doing??? I do have filters and such that I am not using but this is all experimental for now.
    Last edited by Dskeet6; 03-19-2010 at 03:44 PM.

  18. #38
    Senior Tuner Frost's Avatar
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    Quote Originally Posted by Pekka_Perkeles View Post
    It seems that there are opinions having LTFT's enabled or not. That's perfectly fine. I guess it's the same with dialing VE table with either stock narrowband o2's vs. wideband. I've tried both ways and they seem to work....
    If you think tuning via trims is comparable to tuning with a wideband, you haven't spent much time doing it both ways. That part isn't an opinion. I can map 3 VE tables before you can do really do the cruise portion of just one using trims; especially down low on anything with much cam and LTs. Trims make rocky-ass VE tables if you aren't constantly refining by hand too.

    The more I think it about it, I'm not sure how using LTFTs on modded cars is just opinion either. I can make a list of reasons NOT to have them, but I can't really think of a reason TO have them if the car is properly tuned. What is the reason that you would want to keep them?
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  19. #39
    Senior Tuner S2H's Avatar
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    Quote Originally Posted by Dskeet6 View Post
    Yes the MAF is still enabled. I attempted to tune the MAF a few months ago and saw that the greater the cell counts I had, the MAF started towards - percentages I believe(or whatever was desired). So >100 cell counts showed the MAF was fine.... which was strange because I have intake mods upstream of the sensor. Is this normal and what # of cell counts should I rely on???

    This is great information.... thank you. I had no idea that LTFTS carried over into PE if they were positive trimmed. This makes sense because my LTFTs were positive by more than 10%. I just thought it was strange that the WOT fuel(PE) with the LTFTs was what the car was commanding(14.63/1.25 = 11.7) after a few wot runs.

    Ok so I need to tune:

    1.) the MAF via stft?

    2.) then the VE table so LTFTs are slightly positive across the board.
    3.) then PE table...


    Now if trims are + and I make them negative through VE tuning but the wideband then shows its not cruising at 14.6-14.7 then there lies a problem with o2's age possibly??
    you have to disable the MAF first...unplug or set fail to 0..
    then you tune VE...preferrably with the AFR error method (disable and reset all trims and tune with your wideband)
    once VE is done you can re-enable your MAF...
    on the dynamic airflow page you can set it up so that your car uses ONLY MAF(do a little reading...its not hard to do...one main thing..set the value 4000rpm to around 1000rpm...thats the major part)
    then you can tune MAF using AFR Error Method as well...

    once complete...
    go back to normal MAF setting in the Dynamic airflow page...and doubel check tune with MAF and VE combined
    at part throttle your PCM uses a blend of the MAF and VE until it hits the value specified(that 4000rpm value....) then it goes to all MAF

    if yuo still have odd trims...double check that your wideband is correct and re visit VE and MAF table again until its good enough for you


    and its always better to have the trims negative slightly better to be slightly on the rich side than the lean side
    -Scott -

  20. #40
    Quote Originally Posted by 69lt1bird View Post
    You need to tune the MAF with the wideband (AFR error %), tune the VE table with the wideband (AFR error %). Its really that cut and dry.

    Have the LTFT turned off while doing the tuning. Don't worry about the trims until you have the other two dialed in correctly. If you do those right the trims will fall in line.

    The guide in my signature works pretty good and explains some of the naming and what it does. Try that and follow the instructions. Others have had success with it, give that a try.

    I think im starting to get a hang of this.... Thanks alot.... Your write up was very good. I think my MAF is OK but I can verify that after I plug it back in.

    my LTFTs are now negative other than WOT within 1-2%. Im not worried about getting the cruise LTFTS perfect because the car will trim for me(again noting that they should all be negative so they dont carry into PE fueling)... they look OK. I am working on higher rpms now and WOT VE areas before i plug the MAF back in.

    thanks for all the help everyone... I think I am starting to make some real progress.