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Thread: Injector Offset Adder - Clarification

  1. #1
    Fuel Injected! Terminal_Crazy's Avatar
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    Injector Offset Adder - Clarification

    Hi guys, can someone explain the Injector Offset Adder Table
    I'm using the EEXTRA.xdf file for a '95 LT1 8051 pcm. and also Steveo's 3.6 XDF

    OK The Injector Voltage Offset table is pretty straight forward (adjust injector for voltage variations).
    The Injector Offset Adder I understood was to cover the dead time before the injector is fully open.

    I'm wondering if the two headings are swapped around?
    It has two columns:
    Adder (usec) and BPW(usec)

    The fixed column: adder goes from 488usec to 1952usec whilst the BPW is editable

    Can anyone confirm this is wrong in the XDF

    Thanks
    Mitch

  2. #2
    Fuel Injected! jthompson122183's Avatar
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    Is it the same for both xdf I haven't worked on eextra for a few. Or is steveo different?
    97z28 A4 obd1 swap(16188051)
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  3. #3
    Fuel Injected! Terminal_Crazy's Avatar
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    Steveo's are correct i think
    EEXTRA has columns swapped over which had me confused. (Not very hard)

    Mitch

  4. #4
    Fuel Injected! jthompson122183's Avatar
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    Quote Originally Posted by Terminal_Crazy View Post
    Steveo's are correct i think
    EEXTRA has columns swapped over which had me confused. (Not very hard)

    Mitch
    I'll make a note of that. I started with a old version of eex 2.something I think, Bear with as I'm still quite new to learning this stuff. If you have any recommendations or know anything else that is off or know what something is speak up, I'm all ears. My goal with eextra is when comparing files we don't see "Item Not Defined" anymore
    97z28 A4 obd1 swap(16188051)
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  5. #5
    Fuel Injected! Terminal_Crazy's Avatar
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    Cool.
    I'll keep my eyes posted then.

    Thanks
    Mitch

  6. #6
    Fuel Injected! Terminal_Crazy's Avatar
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    What i was actually asking was what does the adder actually do?

    add the usec time to the BPW or deduct it from the calculated time.

    ie. If my bpw was at 1.952 ms and I add 100 into the (1952usec) table would it deduct 100usecs worth of fuel (the amount of injector dead time) from the calculated BPW ??


    Mitch

  7. #7
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    Terminal did you ever find out exactly what effects this has. I have played with it many times but didn't see much if any difference. Some bins have it 381.48 BPW then gradually getting lower to 30.52 BPW while I believe it's the corvette has nearly the same though has 228.88 BPW between 793 - 1464 Adder columns.

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    I have been reading somethings about short pulse adder in HPTuners. I believe it's the same as our adder just called something different in HP. One guy briefly explains it like this.
    The short pulse adder is meant to linearize the injector characteristic for very short pulsewidths, where simply using the injector flowrate gives the wrong result and the injector does not inject the amount of fuel the PCM thinks it is. I don't know and still diggging

  9. #9
    Fuel Injected! Terminal_Crazy's Avatar
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    Hi troutdog311
    I've read a bunch of interesting articles (by Greg Bannish & Injector Dynamics) but not had time to play yet.
    The injectors take a short time to open and then fuel starts to flow taking a time until it stabilises to the injector flow rate.
    (This is a curve from zero upto where the flow/time straightens out).
    I understand the concept but not which way round the figures work.
    In my tune they were all set to zero and presumably adjusted around.

    My thoughts are:
    If the injector takes 500-usec to open and 1000-usec before flow stabilises.
    In Open loop:
    With a BPW of 1000-usec we have 500-usec of no flow and 500-usec of partial flow.
    with a BPW of 1500-usec we'd have 500-usec of no flow 500-usec of partial flow & 500-usec of stable flow.
    so the adders are to make up the shortfall.

    I realise I have been viewing the logs whilst in Closed loop so the PCM would have already compensated for this.

    Thanks
    Mitch

  10. #10
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    Thanks Terminal! I believe you are spot on and makes sense. I'll talk about “my” offset at 12v so I don't have tons of numbers everywhere. I'm using older fat style Denso F55E-A2E 24# "single nozzle". I have spent hours, hours and hours looking for an offset for these and has been very difficult. As we know most all stock offset I’ve seen at 12v is 488usec. I have found the Bosch M-9593-AA302 24# injectors which is .751ms/751usec at 12v and other Ford SVO 24# offsets that are .81ms/810usec at 12v.
    I'll step back a few months when I got my car. It didn't run good at all and had to replace every sensor on this thing and much much more and I'll stick with fueling to keep this post a little shorter. I pulled the bin from my car first thing and noticed it had been tuned somewhat.
    The offset was set to 671usec at 12v and left it this way for a while. I kept having odd split BLMs that I tried every trick in the book to address with no luck and started playing with offset. I decided to set offsets with 701.91usec at 12v and immediately noticed better BLMs and power. I never touched the offset again until yesterday.
    Yesterday I wanted to play around a bit. I always hear people say you can use ford 24# or even 30# with stock values knowing this isn't so I flashed stock values. As soon as I started the car it ran like crap, had no power at all and wouldn't idle well. I know other factors of the tune have to agree with this change but even so it did not like stock offset.
    I then decided to pump my my offset almost 10% “really closer to 9%” above my previous known working Offset in the 6.0-14.0v range making it 762.94usec at 12v. Man my car has never ran so strong and I am very very happy so far. I also forgot to mention I did copy the corvette offset adder for a test in my last log with no noticeable difference.

    Today car is amazing strong! I’m slightly adding to the PE/Timing to see if I can squeeze a little more out. Again trying to make this somewhat short I have spent so much time on every parameter though I’m going back through it all to be sure.

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