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  • Dyno testing is a good idea

    After an addition of headers and elimination of the CC on my exhaust, I thought I'd recheck the power on my rebuilt 2.5L motor. BIG gain in torque, which didn't surprise me as the midrange felt considerably better.

    But the real benefit was noticing the dip in power at 3500rpm - I'd just assumed that was how the motor felt at lower rpm but the graph indicates that there must be an issue with the AFM (probably due to the engine usually operating at that rpm, so perhaps a flap or something gets hung up in the AFM at that rpm).

    Ordered a rebuilt unit and will install when it arrives next week. (Note the solid lines indicate the dyno results before adding the headers and eliminating the CC, the dotted lines are after. Pretty big difference).


  • #2
    Typically the afm doesn't get hung up but the resistive track wears thin/out thereby outputting voltage that is slightly off.

    First off, let me state that I am an electrical technician with over 21+ years professional experience in electronics repair, rework, and restoration. I specialize in custom electronics fabrication and electronics repair. I can build / repair electronics from high current applications to surface mount technology and circuit


    Refurbished afm and indeed you should be good.

    Enjoy her!

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    • #3
      That's not an AFM issue, or any issue, other than you moved the resonating frequencies of the exhaust gas pulses of the 'system'. If you remove the AFM, it will change the graph yet again, and move the dip to another area. Now if you had the ability to tune the ign timing, fueling and the timing of the fueling you can tune out that dip to a certain point.

      T

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      • #4
        I have see that dip and it seems to get more pronounce with increase of engine power over stock, and I agree with Hand built not a function of AFM. I think on a modern engine control system with electronic throttle motor it could be smoothed out by closing back the throttles some amount while over the dip RPM area.

        E30 M3 1987
        Mini Clubman GT
        BMW E36 323 Msport
        Toyota Corona
        KTM 200EXC
        Honda CB50 (1979)

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        • #5
          We're also talking to our chip guy to see if he wants to modify the chip

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          • #6
            Agreed with the others, there was no dip before the mods, so I dont think the AFM just went bad

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            • #7
              Although it cant hurt to have a new AFM, as they don't seem to age well anyway.

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              • #8
                Update - Installed the refurb'd AFM and problem solved. The car pulls nice and strong now from 3k up, not to diminish some of the helpful comments here but the issue was the AFM.

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                • hardtailer
                  hardtailer commented
                  Editing a comment
                  Thanks for reporting back! Helps putting effect and cause in the ' collective database' that is s14net

              • #9
                Glad you got it figured out!

                Weird that it was the AFM still. Seems like it failed between the two dyno sessions!

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                • #10
                  be interesting to see another dyno run with the new AFM.......

                  T

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                  • #11
                    Originally posted by HANDBLT View Post
                    be interesting to see another dyno run with the new AFM.......

                    T
                    It's tempting, but not sure I need to spend $250...

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                    • #12
                      then how do we know the dip is gone?

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                      • #13
                        Originally posted by ADA///M View Post
                        then how do we know the dip is gone?
                        Butt dyno is free and not data driven!

                        Glad the AFM seemingly fixed the issue.

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                        • #14
                          Originally posted by nabragg034 View Post

                          Butt dyno is free and not data driven!
                          and super accurate

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                          • #15
                            Did my first long drive with the car today, it runs better no doubt. AND gets better fuel economy.

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