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  • Bang and pop after shifting down

    Hi,

    I‘m running RS2 spec with 1,9 bar overboost to 1,5 bar. I have rs2 injectors, FPR and cams installed. The exhaust is equipped with a metall catalyst and stainless steel bn-pipes. The car runs fine, but if I shift down from higher gears to lower gears (like to second) and the vehicle speed revs the engine up, I get random pops and bang from the exhaust. Seems like mixture ignites in the exhaust. I don‘t like it, but i don‘t know how to fix it...

    I tried to lean/enrich the mixture with the correction table in the first column (lets say first four load cells..) but this didn‘t help. I also tried to advance the timing for this load area (my thaugt was, if mixture ignites in the exhaust, the timing was too retarded). But it also didn‘t solve the random explosions.

    Does anyone have an idea, whats the root cause here and how to fix it? Is there anything to tune the overrun cutoff?

    Best regards,

    Daniel

  • #2
    There are like a million kids who would wish they would have this.

    Anyway during overrun there is a different ignition table used, not the main one.
    If you modify that to something like 0 degrees instead of the low values that there are, it will most likely take care of it.
    Or you can change fuel cutoff delay to be more aggressive.
    http://tuner.ee - http://www.facebook.com/tuner.ee

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    • #3
      Yeah, but I got this behaviour for free, with just using the stock rs2 calibration

      Good hint. I think the timing is ramped in steps from retarded side to the value of the main table. And this transition I would like to to tune..
      If you say set to 0, you are not talking about the standard rpm/load based ignition tables, right?
      I know 3 ignition tables, main one, one for continuous knock and third is overrun, but i think this limp home. Not meant for standard overrun cut off.

      BR

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      • #4
        Log your ignition on overrun, and you will see. The overrun table is active.
        You think wrong about "limp mode" such a thing does not really exist. Only in the boost/knock chip is the ignition retarded if a knock sensor is faulty or hall sensor is faulty.
        http://tuner.ee - http://www.facebook.com/tuner.ee

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        • #5
          Hi prj,

          if you mean the big ignition map at 0x90A8 (0x9084), it‘s not read by my ECU. I don‘t have any adress hits there..
          But what I could observe is that as soon as the throttle idle switch closes, the smaller „ignition for closed throtle“ map is active. It is also active outside of idle when the engine is in overrun cutoff. And my bang and pop events happen with closed throttle plate.

          I recognized a difference in this map in comparison to the stock rs2 file (i changed it earlier by myself, i don‘t remember why..). It seems to fix the issue a bit to go to the stock values.
          Anyway the factory calibration of this map is not so well in my view...

          BR

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          • #6
            Check out the ZW_OUT thread, this will help you to find the ignition angle which is used
            You have different "ZWB" for different driving conditions (table angle is loaded into a var but not used at the end).

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            • #7
              Hi Acki,

              I had a look at this thread. Seems to me that „KFWLL“ is active when B-LL (idle) or B-SA (overrun cut off) is active.

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              • #8
                It's the same on a warm engine
                Ignition timing 20/25° and you don't have the "lean pop".

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                • #9
                  It still happens...
                  It clearly sounds like something detonating in the exhaust. I don't know if this is even ignited by a spark plug. high likely due to the heat of the exhaust..

                  BR

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                  • #10
                    Do you have a logfile?

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                    • #11
                      How i did it was to force fuel on all the time on deceleration all the time and used a little bit of custom code to force RAM_54 and RAM_58 to false values on deceleration making the a truly negative value all the time. only problem i seen with this method was that the ECU sometimes had slowly returned to its normal ignition angle degree. slightly annoying but can be dealt with. also it appeared that sometimes it wouldnt do it though everything was proper and what i came to was ISV code needed to be modified to let more air into the intake as well because if i leaned on the throttle just a tiny bit on decel to let more air in it would pop and bang violently. over all fuel mileage was horrible with it so i abandoned it.
                      "The really good drivers got the bugs on the side windows." Walter Röhrl

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                      • #12
                        Have to bring this up again because I finally had the time to take a look at this.
                        My conclusion from all of this (OEM RS2 and NOT prjmode):
                        When getting "off throttle" (+some parameters):
                        - Ignition is decreased by Overrun Function
                        - Ignition map is switched from KFZW to KFWLLK (B_SA)
                        - KFWLLT is activated (B_SA)
                        - Ignition output is the result of addition KFWLLK + KFWLLT (I´m just ignoring GE, LLRR and AR at this time)
                        - Ignition is limited by WMINN and WMAX
                        - WMAX can be ignored
                        - WMINN is -5,75 OEM

                        KFWLLK on hot engine is always 0 deg
                        KFWLLT on hot engine is always 0 deg

                        I don´t get this:
                        If you modify that to something like 0 degrees instead of the low values that there are, it will most likely take care of it.
                        because no negative values is these maps on hot engine (OEM rs2 code).

                        Fuel Injection is still active until TVSA Timer is reached. OEM = 0,0s

                        So maybe:

                        TVSA from 0 to 1,5s
                        WMINN from -5,75 deg to -20,00 deg f.e.
                        KFWLLK from 0,00 deg to -20,00 deg (hot engine >1600rpm) f.e.

                        Some opinion about that??

                        best regards

                        PS in prj mode there is a map called Ignition - "P/T, overrun" but OEM it is "Safety Ignition Map when faulty Idle Switch".
                        I dont know if this map is used for P/T in OEM file....

                        Last edited by blackS2; 28 January 2021, 11:52.
                        [__]=oooo=[__]

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                        • #13
                          Please, can you help me locate TVSA and WMINN maps in the RS2 or PRJ software. I mean map addresses. Thanks

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                          • #14
                            fiy they dont do this stuff very well swinging from a negative timing value to a positive value quickly. you end up with this sort of lag when the timing is trying to swing back positive that is very noticeable when driving. if you want to try it set the value at 0x839F to FE. this is the timer for fuel being on when deceleration starts. max is 2.55 seconds. stock this is set to 0 so its instantly off. go into the idle ignition table and set the first 3 in the row at 3000RPM to -5.25 degrees. this will give the the effect you desire with the side effect of the slow recovery from negative to positive timing. your welcome.
                            "The really good drivers got the bugs on the side windows." Walter Röhrl

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