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Thread: Adjusting Fuel Trims

  1. #1

    Question Adjusting Fuel Trims

    Does anyone know what Long Term and Short Term trims typically read?
    Currently I have LTFT +9.4% and between 0 - 5% STFT when cruising.

    How can these be adjusted with the Standback?

  2. #2

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    Anyone have an answer?

  3. #3

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    There is no such thing as typical as each car could have different LTFT and STFT based on altitude, fuel, what angle your air intake is, how dirty your filter/MAF is. Ideally you want 0, but really as long as you're not throwing a CEL which in itself is an arbitary value of +/- 20 or 25% ltft/stft, then there's no issue. I don't believe there's much benefit to actually tuning it out.

  4. #4

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    I think the CEL is produced over +25%

    I had mine upto +20.4% when I had a 3" intake fitted.

    What mods do you have? Try removing them 1 by 1 to see what causes the increase in values.

  5. #5

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    Quote Originally Posted by 2XS View Post
    What mods do you have? Try removing them 1 by 1 to see what causes the increase in values.
    Thanks for your thoughts guys.
    I am totally stock except the standback at this stage. I have cleaned the MAF sensor and it made no difference.

    Funny thing is, when I unplug the standback and use the bypass plug, the trims appear to be within the zero to 5% range.
    I am trying to track down why the standback has introduced up to 5° knock retard sometimes on light throttle. There are no apparent leaks in my intake system.
    Last edited by Syd_Chrome; 16-12-2009 at 05:23 PM.

  6. #6
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    Interesting, regarding Knock Retard on the Dashhawk - what fuel are you running Syd? As I've noticed sometimes with mine, when running Shell 95 octane the KR can be as high as 4 occassionally, but with 98 there is no KR warnings! Though have had a couple of instances from my local BP (Manning Road) where the KR has registered 2-3, so would probably put this down to bad fuel on these occastions. Only mod I have is a CP-e CAI, I'll have a look at my fuels trims and post these for you
    R36 - Just like an MPS6 except with a growly V6

  7. #7

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    Quote Originally Posted by shakespeare View Post
    Interesting, regarding Knock Retard on the Dashhawk - what fuel are you running Syd?
    I always run 98. I think the standback has modified the MAF sensor voltage and the ECU is correcting it, having to "richen" it up but is a little slow at times, thus causing an occasional knock.

    Regarding the Knock retard reading - I am still unsure that KR actually means detected knock or that the ECU just retards timing before knock MAY occur as a precaution.

    Quote Originally Posted by shakespeare View Post
    Only mod I have is a CP-e CAI, I'll have a look at my fuels trims and post these for you
    That would be great if you would.

  8. #8

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    What map are you running on the standback. Is it a zero'd out map with increased boost, or has there actually been some custom tune done by the CP-e guys?

    Also knock retardation is not in %, it's in degrees and is the opposite effect of advance ignition timing. If you advance your timing too much, you run hotter which causes knock, which then causes the ecu to retard it back to a level where you shouldn't be knocking. You'll also notice a ton more knock when the weather gets hot. When I was driving to my friend's house a couple of weekends ago, I was get KR readings of upto 5 pretty much every time I was on the throttle.

    Like I said earlier, comparing fuel trims with other people serves no purpose - especially if you're stock and they're not. My fuel trims changed just by changing my intake brand.
    Last edited by Nuliaj; 16-12-2009 at 05:12 PM.
    Nuliaj: Hatches are only really half a car anyway.
    shinslinger66: And you forgot to add that they are also a girls car!

  9. #9

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    Quote Originally Posted by Nuliaj View Post
    What map are you running on the standback. Is it a zero'd out map with increased boost, or has there actually been some custom tune done by the CP-e guys?

    Also knock retardation is not in %, it's in degrees and is the opposite effect of advance ignition timing.
    SB Map is zeroed out. Just running SB as a boost controller so far.

    and... Yes, I must have been typing fast and not realised I said % instead of degrees.

  10. #10
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    Hi Syd,

    Some analysis of my fuel trims, as mentioned only mod I have is the CP-e CAI

    Idle (running temp 83 degrees)
    LTFT -10.5%
    STFT - 4.7%

    Cruise (100kph in 6th)
    LTFT -3.1%
    STFT 0 to -2.6%

    WOT (2nd/3rd)
    LTFT 0%
    STFT 50%

    I'll try and do some data logging and post the graphs soon.
    Cheers
    Chris

  11. #11

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    Quote Originally Posted by shakespeare View Post
    Hi Syd,

    Some analysis of my fuel trims, as mentioned only mod I have is the CP-e CAI
    Cheers, thanks Chris that helps me heaps. I am going to try now and optimise my cruise trims before I start WOT tuning the Air/Fuel ratio.

    Syd.

  12. #12
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    Hey Syd, how'd you go with the fuel trims? Here's some information I came across recently

    The Value of checking your LTFT - Mazdaspeed Forums

  13. #13

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    Hi,

    Thanks for the link.
    I have been slowly adjusting them with the standback and have found that the knock retard under partial acceleration is much, much better. I am still trimming things a little and will be starting final tuning soon.
    Regards, Syd

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