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Running very rich, is there a way to tune stock AFM?

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    #1

    Running very rich, is there a way to tune stock AFM?

    Hi guys,

    Since I bought my e30 (325i with m20b25) I've known it was running rich, but didn't know how bad it actually was. Installed a wideband sensor today (planning to put it on megasquirt in the next couple months) and it confirmed my suspicions. At idle (fully warm) it sits at 11:1 or lower, and stays around 11 - early 12s under acceleration, sometimes lower, never higher. Even just cruising in gear off the throttle it is about 12...

    Car has 288 Schrick cams and larger injectors (which I thought were 19lb/hr, but might be higher) running on stock motronic. As said I do plan on putting it on megasquirt standalone soon so should be able to tune it properly then, but just wondering, is there an easy way to make it run a little less rich in the mean time? Would it just be the larger injectors causing it to run so rich, or would it be something else? My fuel consumption is absolutely horrendous, and running this rich can't be good for anything, so I'd like to sort it out

    Cheers
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    #2
    The larger injectors w/o a proper tune and probably the major cause of the rich condition. If everything else is the engine/management system is working properly and the O2 sensor is good you can get away with 17lb injectors on the stock tune. Anything greater will run rich.

    The first thing to do would be to install a good set of OE injectors. Unless there has been serious increase in mass flow through the engine (serious internal engine work or forced induction) the OE injectors are plenty big enough.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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      #3
      might try a set if standard ones and aee how much better it is. i plan to be doing serious engine work in the future, but for now it's relatively standard except for the cams (as far as I know).

      The ecu actually died recently, so had ir sent away and repaired, it was running tge same before that though. Afm seems ti be okay but im not sure, tested it with power going into it and it steadily increased as it was opened. have noticed a slight crack in the intake boot(not sure if it goes all the way through, might just be cosmetic), but if it had a vacuum leak wouldn't that make it lean at idle instead of rich?

      Sent from my GT-I9305T using Tapatalk 2

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        #4
        Or buy a chip with a tune for 19lb injectors.

        Sent from my C771 using Tapatalk 2
        sigpic

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          #5
          As said ill be putting it on megasquirt in the next few months, so no point buying another chip before then.

          Had a play around with the Afm the other day, tightened up the spring tension quite a lot of clicks and adjuated the idle screw a little, idles at 14-15 now and is still a bit rich at higher revs at WOT but a lot better than it was. Might have a bit more of a play with it some time, but its quite easy to adjust for those interested.

          Sent from my GT-I9305T using Tapatalk 2

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            #6
            Did you mark the original position? if not that AFM will never work as intended again.
            Bosch laser tune every AFM board with each spring.

            Anyway if your car runs better tunning an stock AFM you are covering the real problem (intake leak, fpr on his way out, something else).

            good luck with the mega!!

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              #7
              Originally posted by mgromero View Post
              Did you mark the original position? if not that AFM will never work as intended again.
              Bosch laser tune every AFM board with each spring.

              Anyway if your car runs better tunning an stock AFM you are covering the real problem (intake leak, fpr on his way out, something else).

              good luck with the mega!!
              I can confirm this as well. Adjusting that spring tension will throw off the calibration big time.

              I sell refurbished AFM's to the community but never sell any with the spring adjusted. Those go to automatic fail.

              Also you can't reliably test an AFM with a meter. Only an oscilloscope. A digital meter does not have the resolution to "capture" a voltage drop that most often occurs in microseconds. Also digital meters provide you an average feedback, not real time.

              I would double and triple check you have no vacuum leaks, smoke test!
              Owner - Bavarian Restoration
              BMW and European Electronics Repair and Restoration
              www.BavRest.com
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                #8
                I sent you another PM Greg

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                  #9
                  Thanks for the advice guys, I realize that it is probably just covering up an underlying problem, but that's better than nothing. I did mark the original position, but I have a feeling it was played with before I owned it, it's definitely been opened before, there was no sealant around the cover of the afm. I think there's a vacuum leak in the intake boot, but ill be replacing that and the afm and such with custom piping when I go to megasquirt so can't bring myself to spend money fixing up the stock stuff for a few weeks of use, might try a ghetto home cancer giving smoke test though to see if theres any leaks

                  Sent from my GT-I9305T using Tapatalk 2

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                    #10
                    Just shoe-goo your intake boot for now.

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