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K values, z32 AFM and live edit

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  • K values, z32 AFM and live edit

    according to jasons site: "If you use larger injectors you will want a smaller K. A larger AFM will cause the need for a larger K. If you do both a larger AFM and larger injectors, you might not need to change the K all that much."

    the stock K comes out to 607DEC. i have a z32 AFM and 450cc DSM injectors. i loaded up a BIN that someone uploaded using this same setup and his K is 304DEC. thats just about half of stock.. shouldnt it be a lot closer to stock? does this sound like a reasonable number? the car does run, and it seems to be ok, but i havent taken any logs yet. it just seems like it should be higher. any input is appreciated here..

    Also, using the formula on Jasons site for estimating K for larger injectors i get 342DEC for my 450cc injectors with a stock AFM... when i "commit AFM changes" for the z32 AFM it tells me that changes were made to the K, VQ map and AFM limiter, but no changes are actually made to the K. shouldnt the K increase when i select a larger AFM? no matter what changes i make or what order i make them in, when i select Z32 afm, no changes are made to my K value when using livedit. if you can explain this to me it would be a help.

    and finally... when i change the K value i dont just type it in, i use the injector resize option in live edit with the assumption that livedit changes the tp scales for me and things like that. for example, i know that my estimated K with a stock AFM was 342DEC, and some trial and error showed me that 461CC injectors come out to 342DEC. is my thinking screwed up here? if anyone wants to suggest a K value for a Z32 AFM and 450cc injectors it would be much appreciated. thanks

  • #2
    Two things I think people are misunderstanding is that liveedit will make your K value correct using the adjustment feature and than an AFM change will require a drastic K change. I simply ignore it, adjust the K manually until it matches the wideband, then adjust dwell time if needed. The k value that LE comes back with is always going to be SUPER rich for some reason. Do the TP scales yourself as well, I don't think I ever had or even noticed liveedit changing mine...


    • #3
      Try a K near 300Dec or lower. Like Jason said the wideband will tell you what you need to do. The amount you need to change the K by based on an afm swap is determined by the exact flow characteristics of the afms. Nobody really knows exactly how much any of the afms are good for so they are only guessing as to what they flow and therefore guessing what the K should be. That's all LE is doing.


      • #4
        well if you took a run down the street datalogging afrs... before swapping

        then did it again after swapping and guessing the k value/dwell.... you keep adjusting til you get the same afrs and you should have found it

        since we have official vq maps for the z32 afm this should be the most accurate way of getting a k value

        then once you have it you can start playing with the tables


        • #5
          I've found from going back in forth with the z32 bin files and chating with other Z32 guys that the K value for dsm injectors which at our pressure is 420cc not 450cc (DSM lied to us :evil: , lol) . the K works well at 304 which is where mine is but a K 254-245 is right on but I think it's best to stay with 304 unless you have a wideband and are ready to tune in the car. I did try the 254 and was fine with 14psi on my t3/t4e at 20 degress but was detonating when I moved timing to 24. so I'm running 304 until I get my wideband (When ever the USP guys delivers it, lol )

          Blue & Silver 81 zxt, 88 ECCS
          Z32 mas,450cc injectors
          ported exhaust manifold, cable throttle linkage
          t3/t4e 12psi , 3inch exhaust, K&N,
          ACT clutch, 240sx t/b, 1G DSM BOV
          Custom Intake FINISHED
          Ported and Polished N42
          Tan 88-89 conquest seats
          Sperco IC 18.5x6x3.5
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          Suspension work!!
          Zeitronix Wideband
          240sx transmission
          95 Maxima Alternator