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Guide to your OBD2 swap! Diagnostics and logging

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    Guide to your OBD2 swap! Diagnostics and logging

    So we have questions from customers from time to time on how to acutally utilize their fancy OBD2 diagnostics. Ill keep this thread updated but its currently just thrown together off the top of my head.


    For this you have a few different options.

    The most simple/common is to get a 20pin adapter for the obd2 port:

    Cheapest here

    From there you will need something to feed you data. If you want the most simple setup you should look into a simple OBD2 wifi dongle (or Bluetooth for you android guys)

    Found here


    From there you can get the torque app, or something like OBD2 fusion.

    Another alternative is to get a OBD2->USB cable like this one:

    found here

    Which will enable you to hook your car upto a laptop and utilizie software like INPA, testo (found here) or Romraider/logger


    Once youre able to grab all this data what does it mean and what can you do with it!?!


    First and formost is the most common cause of CELs is vac leaks. These spit codes for fuel trims and whatnot. Using your fancy new tools you can get some feedback on what is really going on.
    (Pcode list for those using OBD2 scanners)

    OBD2 Speak:
    STFT: This is instantaneous fuel trim and will bounce around while idling and driving.
    LTFT: This is learned long term adaption based off a rolling average of sorts for STFT.

    BMW Speak:
    Lambda Integrator: Same as STFT
    Additive Trim: This is long term learned STFT for IDLE conditions
    Multiplicative Trim: This is long term learned STFT for Cruise Conditions

    To put it simply the bmw additive and multiplicative are added together to output OBD2 LTFT data.

    Now that i understand that, why the hell is my CEL coming on?

    Basically fuel trims add (+) or remove (-) fuel to the base fuel map based off O2 sensor feedback. The MAF sees a certian amount of air coming in, grabs a position on the fuel table based off that airflow and RPM and injects a specific amount of fuel. The O2 sensors then watch to make sure that amount of fuel injected matches the target AFR (which is usually 14.7 or stoic). For 100 different reasons its not always perfectly precise, so the fuel trims add or take away from the base fuel table to try to achieve the target AFR.

    When you have a vacuum leak youve now really confused the system. Unmetered air that the ECU is unaware of is now entering the engine. Its burned and passes to the O2 sensors which now see all this extra air and assume that the base fuel map needs adjusting and begin to trim that section of the fuel table (again RPM vs airflow). It will begin adding fuel to compensate for the extra air its seeing even though technically it doesnt really need the extra fuel. This causes rough running and horrible MPG as the ECU is pouring fuel unaware that an otherwise *normal* amount of air is entering the engine, its just missing the MAF.

    Other possible issues that the ECU will try to 'fix' are, wrong sized injectors for the tune, low/bad fuel pressure, clogged injectors, etc. These situations can cause both + and - Fuel trims..

    From there going further into diagnosing the 'health' of your setup you can get into data logging. Which basically grabs a number of data points from various sensors and plots them for you to analyze. Will go into further detail on this:

    Check Us out on Facebook
    Needing a harness adapter or wiring help? Check it out: also have 24v motor mounts, E30 M3 covers and E36 ECU mounts!
    Full Product Line Tuning
    OBD2 Tuning Available! OBD2 E36, S54 Swap, S62 Swap, etc: tuning@MarkertMotorWorks.com Dyno Thread

    #2
    Reserved

    Check Us out on Facebook
    Needing a harness adapter or wiring help? Check it out: also have 24v motor mounts, E30 M3 covers and E36 ECU mounts!
    Full Product Line Tuning
    OBD2 Tuning Available! OBD2 E36, S54 Swap, S62 Swap, etc: tuning@MarkertMotorWorks.com Dyno Thread

    Comment


      #3
      In for myore info. Good info

      Comment


        #4
        No one seemed interested. Damn E30 kids :P

        I guess same reason people buy kassel tunes with no supporting data behind them other than popping up first on google :0

        Check Us out on Facebook
        Needing a harness adapter or wiring help? Check it out: also have 24v motor mounts, E30 M3 covers and E36 ECU mounts!
        Full Product Line Tuning
        OBD2 Tuning Available! OBD2 E36, S54 Swap, S62 Swap, etc: tuning@MarkertMotorWorks.com Dyno Thread

        Comment


          #5
          might be we just did not notice the thread till now.
          https://www.facebook.com/BentOverRacing

          Comment


            #6
            ;) Getting old angry and jaded

            Check Us out on Facebook
            Needing a harness adapter or wiring help? Check it out: also have 24v motor mounts, E30 M3 covers and E36 ECU mounts!
            Full Product Line Tuning
            OBD2 Tuning Available! OBD2 E36, S54 Swap, S62 Swap, etc: tuning@MarkertMotorWorks.com Dyno Thread

            Comment


              #7
              Great info here.
              I was just researching trying to troubleshoot unset sap and evap readiness monitors.
              I'm hoping INPA will give me better visibility into what the sensors are doing during test periods.
              Project
              Feedback

              Comment


                #8
                Just noticed this thread. Good info as always Dave.
                Originally posted by priapism
                My girl don't know shit, but she bakes a mean cupcake.
                Originally posted by shameson
                Usually it's best not to know how much money you have into your e30

                Comment


                  #9
                  Man I am all about this. Any more info would be great.

                  I briefly messed around with INPA on my e90 but I never really understood what the hell I was looking at. Any good resources on the basics?
                  Thank god, R3V was getting boring since the ginger kid wrecked his car. - Stonea

                  Comment


                    #10
                    It's been in the 50's here this weekend. I got the lower temp fan switch installed and confirmed the fan kicks on now so I figured I'd take the car out for a drive and try to figure out the data logging feature on the DashCommand app.

                    Alas... apparently since I have a Mac, there's no way that I'm aware of to get the data logs off of my phone I'm using the GoPoint BT OBDII dongle thing.

                    Anyway i tried to record the 'live' data as best I could in my head and noticed the STFT seems to be all over the place. It hangs at +28% for several minutes at a time and the goes back down to -28% for several minutes and back and forth from one end to the other. The car seems to run alright though I have noticed there is a bit of a hesitation/stumble off idle. The car will intermittently throw codes for P1188/1189 which from what I can gather online is a "fuel control" code. Codes for P0170 and 0172 (I think) will also show up as well.

                    The O2 sensors are brand new, FPR on the rail is brand new. Injectors are freshly rebuilt. All rubber hoses for the intake/throttle body area are new. Could the swing in the STFT still be from a vacuum leak? Even when holding the throttle (during highway cruising) it still fluctuates back and forth. Oddly, once I cleared the codes with the app the check engine light never came back on during the 25 minute drive.

                    This is my first time delving in to diagnostics like this but any help would be appreciated. Thanks!
                    -Geno

                    '87 325is (s52'd)
                    '95 525iT
                    '02 Range Rover 4.6 HSE
                    '98 Disco 1

                    Comment


                      #11
                      Stock MAF? O2 sensors plugged in correctly as far as Bank 1/2? Whos tune?

                      Check Us out on Facebook
                      Needing a harness adapter or wiring help? Check it out: also have 24v motor mounts, E30 M3 covers and E36 ECU mounts!
                      Full Product Line Tuning
                      OBD2 Tuning Available! OBD2 E36, S54 Swap, S62 Swap, etc: tuning@MarkertMotorWorks.com Dyno Thread

                      Comment


                        #12
                        ive purchased a bluetooth obd2 adapter, cant seem to get it to work. I am wondering if i cut out an important diagnostic wire.

                        I havent tried a standard obd2 reader, just the bluetooth one (i tested it in my wifes '11 volvo andit works there)
                        Your signature picture has been removed since it contained the Photobucket "upgrade your account" image.

                        Originally posted by TimKninja
                        Im more afraid of this thread turning into one of those classic R3v moments, where Pizza gets delivered.

                        Comment


                          #13
                          You have an OBD2 port wired or are you using the 20 pin? The 20 pin setup may require having the switched power run to it though i dont know why. (pin 6 C101 usually)

                          Check Us out on Facebook
                          Needing a harness adapter or wiring help? Check it out: also have 24v motor mounts, E30 M3 covers and E36 ECU mounts!
                          Full Product Line Tuning
                          OBD2 Tuning Available! OBD2 E36, S54 Swap, S62 Swap, etc: tuning@MarkertMotorWorks.com Dyno Thread

                          Comment


                            #14
                            Just ordered a wifi adapter and OBD Fusion for my phone / ipad. Looking to figure out more on the data logging once I get it all set up and gong. . .hint, hint. . .
                            Thank god, R3V was getting boring since the ginger kid wrecked his car. - Stonea

                            Comment


                              #15
                              You get the 20 pin adapter cable or do you have an OBD2 port?

                              Check Us out on Facebook
                              Needing a harness adapter or wiring help? Check it out: also have 24v motor mounts, E30 M3 covers and E36 ECU mounts!
                              Full Product Line Tuning
                              OBD2 Tuning Available! OBD2 E36, S54 Swap, S62 Swap, etc: tuning@MarkertMotorWorks.com Dyno Thread

                              Comment

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