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Thread: Adding a "semi active valve" to Supertrapp?

  1. #1
    Tadek Guest

    Default Adding a "semi active valve" to Supertrapp?


    I would like to start a new thread for this topic.

    As mentioned in my other thread, I believe that my Buell X1 is too loud for German authorities when running the 2.5" US header with 4" internal disc Supertrapp muffler and an adequate number of discs.

    Therefore I considered removing some discs and installing a "semi active valve" additionally to the discs. Those valves are for example installed in the exhausts of VW Polo GTI cars. This is a spring preloaded poppet valve with an integrated diaphragm actuator. Once a certain back pressure is reached, the pressure acting on the actuator causes a force which is higher than the spring preload and the valve opens therfore opening an additional cross sectional area.
    If you would like to get a better idea you can visit the following website, which shows a drawing of this valve:
    Unfortunately I could not find an english version of this article.

    I have one of those valves and I think it would fit into the 4" muffler behind the discs.
    Could you tell me how much back pressure is caused by a Buell running a supertrapp muffler at full load? I believe you need approx. 200mbar for the valve to open.

    What do you think of this?

    Best regards,


  2. #2
    bschultz Guest


    The core assembly used in the X1 mufflers are 2.5", the same as the collector. The only restriction/back pressure that is created is determined by the amount of discs (+end-cap) you attach to the end of the muffler/core.
    We do flow testing; however do not get into back pressure testing.
    You would most likely find the information you are looking for from the Engineers at Buell that built the motor.

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