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  • about motronic 1.3 EMS

    well gentlemen, here comes the 1 million dollar thread .

    I've been around a lot of EMS: bosch, IAW, Weber/Marelli.

    To compute the air mass going into the engine (theoretically) we've to get

    p=pressure
    v=volume
    T=temperature

    so we can meter the mass = M = pv/RT. (R is the gas constant)

    The AFM in our s14 cars can only meter volume and temperature, as hot wire AFMs (except those which have the MAP (or APS = air pressure sensor) sensor in them).
    In the EMS that do not have AFM, we always see MAP + ATS (air temperature sensor) + TPS (Pot).

    In those EMS the three parameters above are well determined.


    So, supposing that s14 hasn't any MAP we should think that EMS on our cars are not pressure-sensitive (?).

    Does anyone of you know what's the deal?

    Maybe the pressures are first experimentally determined and then written on the EPROM like injection time and ignition advance maps depending on engine speed (SS) and load (TPS position)?

    Or do we have an EMS with density correction vs temperature, so we can do:

    density (vs t from ATS) x volume (Pot in the stock AFM) = Mass?

    thankssssssssssssss
    power is nothing without drift

  • #2
    The motronic used on the M3 adjusts for pressure also via an external barometer mounted on the airbox.

    88 M3 - LACHSSILBER/M TECH
    89 M3 - ALPINEWEISS II/SCHWARZ
    85 323I S52 - ALPINEWEISS/SCHWARZ
    91 M TECHNIC TURBO - MACAOBLAU/M TECH


    Comment


    • #3
      ok...

      i know but i've seen that that's the altitude sensor, it certainly adjust, but not in the quantity needed for the pressure variations during the running.

      In fact it is not linked by a little hose to the intake manifold as it happens in pressure sensitive EMS.

      Any ideas?
      power is nothing without drift

      Comment


      • #4
        The Moronic used on the E30 M3 measures the amount of air and the temp vs. others that measure the mass and temp. then there are numerous lookup tables in the ECU that use only RPM/AFM volts/air temp/coolant temp/baro. Since there is not a true TPSensor it estimates load based on RPM/AFMvolts.

        T

        Comment


        • #5
          ok...

          So it's almost what i said, there are corrections, based on experimental results, like the ignition and injection maps...
          power is nothing without drift

          Comment


          • #6
            Re: ok...

            Originally posted by france320isco
            So it's almost what i said, there are corrections, based on experimental results, like the ignition and injection maps...
            Correct, fuel metering is calculated by assuming certain constants. This is why the mixture may not be idealized in all situations and must be corrected (within boundries) by the O2 sensor.

            Comment


            • #7
              by the O2 sensor...

              Yes i think you're talking about the lambda sensor, but i dont have it (i've a 320is S14B20).

              But the concept is clear.

              These problems have come to me when i tryed to switch the stock AFM with a TPS + ATS taken off from a Weber/Marelli EMS that is AFMless.

              I actually modified the TPS to fit the butterfly shaft, and set a sort of angular barrel to made corrections for the idle speed by acting on the TPS (the original throttle switch was still in place).

              i've to say that the idling was right and also the high rpm (>4500) but it was really a bad deal in the mid range.

              The TPS and the stock AFM are both linear potenziometers from 0 to 5V and they are 5V powered, so i tought that the problem could be in my ATS, but i 'bridge' it to the original one and the problem was still here.

              So the problem should be in the fact that the stock AFM volts are referred to the air conditions in the AFM and the TPS volts, that are the same signal, are referred to the air in the throttlebodies which ECU is not aware of cause it is based on 'constant' values.
              power is nothing without drift

              Comment


              • #8
                Re: by the O2 sensor...

                Originally posted by france320isco
                Yes i think you're talking about the lambda sensor, but i dont have it (i've a 320is S14B20).

                But the concept is clear.

                These problems have come to me when i tryed to switch the stock AFM with a TPS + ATS taken off from a Weber/Marelli EMS that is AFMless.

                I actually modified the TPS to fit the butterfly shaft, and set a sort of angular barrel to made corrections for the idle speed by acting on the TPS (the original throttle switch was still in place).

                i've to say that the idling was right and also the high rpm (>4500) but it was really a bad deal in the mid range.

                The TPS and the stock AFM are both linear potenziometers from 0 to 5V and they are 5V powered, so i tought that the problem could be in my ATS, but i 'bridge' it to the original one and the problem was still here.

                So the problem should be in the fact that the stock AFM volts are referred to the air conditions in the AFM and the TPS volts, that are the same signal, are referred to the air in the throttlebodies which ECU is not aware of cause it is based on 'constant' values.
                The stock TPS is not a linear pot. It is a switch. Closed at idle, then open from off idle to around 80%, then closed again for full throttle signal.

                T

                Comment


                • #9
                  Above a certain rpm, the AFM is maxed out and the rpm is used.


                  BTW, here's some info on the atmospehric pressure sensor:
                  http://www.iigomotiv.com/barotech.aspx

                  Comment


                  • #10
                    This is what you need to sucessfully complete your removal of the AFM. There are many of us here running the setup.

                    http://www.maxx-automotive.com/ftp/a...yerplus00e.pdf

                    Comment


                    • #11
                      thank you everybody

                      i know that our pot is not a pot , my english is rusty, maybe i didn't make myself clear.
                      Thanks for all the links and informations. It's a barometric pressure sensor, not a MAP or APS like i said and i'll check it .

                      Does anyone of you tryed this?

                      http://home.t-online.de/home/Pro-Auto/startseite.htm
                      power is nothing without drift

                      Comment


                      • #12
                        Originally posted by ColinM
                        Above a certain rpm, the AFM is maxed out and the rpm is used.


                        I've logged several WOT runs thru the gears all the way to redline and the AFM NEVER maxed out.


                        francisco,
                        this hot wire MAF does measure mass as it's the mass of air that's decisive in the current required through the wire to keep its temperature constant

                        Comment


                        • #13
                          thanks again...

                          ...the hot wire AFM, but the only thing that is related to the variation of the wire temperature (and so resistance) is the velocity of the incoming air that multiplied by the section of the AFM gives us the volumetric flow per second.

                          I can understand that due to the fact that there is also an ATS, providing a 'table' in the eprom that relates Temperature to density (or some kind of a circuit in the AFM itself), you can multiply density and volumetric flow to obtain mass flow per second.

                          I only would like to know if our mechanical AFM has some kind of circuit that do the transformation volumetric flow => mass flow or the table are stored in the EPROM.
                          Some guy before kindly told me that :OMG: .

                          Well...The eprom storage and/or the ‘AFM circuit’ would probably explain the malfunctioning TPS over the mid range.
                          (another glitch would be the air inertia, maybe the TPS is so faster than the AFM blade in getting volts to the ECU that when the 'new' TPS send his signal the air pressure wave is not came to the throttlebodies yet! In fact the engine dies only when you push all of a sudden from, let’s say, 2000 rpm).

                          Oh...Thanks for contributing,
                          power is nothing without drift

                          Comment


                          • #14
                            wow we are all over the chart on this
                            one?

                            Sorry, you have the AFM and HFM or MAF
                            idea confused.
                            like Bernard said, it is mass that is
                            proportional to the current.
                            This is really not important for you though,
                            so lets forget about MAFs and get back
                            to deleting your AFM question....

                            But before getting to that, also like
                            to say, do not confuse a SPEED DENSITY
                            (MAP sensor vs. RPM) with an Alpha-N
                            (TPS sensor vs. RPM) setup. Nor
                            the purpose of a barometric sensor,
                            which most modern ECU already
                            have on-board. These setups certainly
                            are air-pressure sensitive as long as
                            youve not disabled or disconnected the
                            baro. A combined MAP-Alpha N
                            is conceivable on some setups. But it really
                            doesnt make too much sense on
                            motors with individual throttle bodies
                            and especially with aggressive cams.
                            The desire to use MAP-Alpha N is
                            to *increase* very low part throttle
                            measurement sensitivity --- e.g. where
                            in theory *engine load* is determined
                            using manifold air pressure (MAP) at
                            *very very low* throttle angles and TPS is
                            used above that angle (some have a
                            blending function). In practice, a good
                            TPS proves to be more than adequate for
                            our applications with no need for MAP.
                            In fact, having to take
                            a common average over MAP (of all the
                            throttles) has its own problems too.
                            e.g. lag and existence of strong pulsations
                            (cam induced).

                            Here is what I think your problem is:
                            I presume the weber you are talking
                            about references its internal tables
                            via TPS and RPM. It sounds to me like
                            you intend to convert your motronic setup
                            to "alpha N" and so the problem you are
                            having is due to the lookup tables
                            being referenced via AFMsignal vs. RPM.
                            The AFM signal, on pin 7, is NOT
                            similar or compatible to a straight TPS signal.
                            Therefore, if you just hookup a TPS signal
                            to pin 7, you have to remap the internal lambda
                            map (fuel correction map).

                            Base fuel is still calculated straight from
                            whatever AFM signal you provide,
                            e.g. load = afm/RPM
                            to which several correction terms are added.

                            Your ignition map is directly indexed via
                            load and RPM.

                            Since TPS is not load --> you cant use
                            the stock maps. A "Chip Alpha N"
                            has remapped tables, which is what
                            you are probably looking for. Just remember,
                            each chip has to be done for the specific
                            car. If you try to use someone elses
                            chip and "bias" the fuel map to
                            work at WOT by changing location
                            of the TPS mechanically, you will be
                            off in other areas like part throttle.
                            Not to mention you have to run the
                            exact same fuel pressure and injectors
                            for which that engine was setup.

                            PS. there is also no ICV compensation in the
                            later!

                            John
                            Last edited by John; 04-01-2005, 12:46 AM.

                            Comment


                            • #15
                              thank you very much for clarifications

                              I'm aware of the base technology of only 3-4 different types of airflow meters.
                              Here in italy we call it 'DEBIMETRO' regardless the tecnology that is beyond it (mechanical, optical, hot wire, and another that i don't know the english name!).
                              So i always get confused with MAF, HFM, etc. Cause here we've only DEBIMETRO or DEBIMETROless EMS.

                              Now correct me if the follwing is wrong!

                              The DEBIMETROless EMS uses TPS+SS (speed sensor or rpm sensor)+APS (i think is your MAP we call it 'absolute pressure sensor')+ATS (air temperature sensor) ---> (let's not consider other sensors to keep things easy) ECU.

                              The DEBIMETRO EMS uses debimetro (different types, but always ATS integrated)+SS ---> ECU.

                              Our 'mechanical' (S14 engines) DEBIMETRO gives information about the engine load to the ECU with his potentiometer and his ATS.

                              So you say...

                              "do not confuse a SPEED DENSITY (MAP sensor vs. RPM)..."

                              So the injection/ignition map in the DEBIMETROless ECU maps is APS (or MAP)/rpm based?
                              I was told when we have TPS, ATS, APS the ECU maps is TPS/rpm based and then 'map = table corrected' via ATS and APS.

                              "These setups certainly are air-pressure sensitive as long as
                              youve not disabled or disconnected the baro...."

                              Ok but it is absolutely NOT an APS/MAP sensor cause it is NOT linked to the intake manifold with hoses or something else, but only to the ECU that corrects the altitude variations.



                              In conclusion you're saying that a tuned TPS+a tuned EPROM+a fuel pressure regulator + an ATS will do the job

                              and

                              that you can't simply makes things better by fitting a 'tuned' TPS on the throttlebodies shaft + an ATS on the intake side because our AFM is able to send, metering air flow 'A' and temperature, the air MASS signal to the ECU, obviously multiplying with some density/temperature table, A and density.

                              thanks again
                              power is nothing without drift

                              Comment

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