View Full Version : Adding a "semi active valve" to Supertrapp?

12-16-2009, 02:06 PM

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,


12-16-2009, 03:39 PM
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.