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Forcing muffler valves closed - Is there an easy method?

1051 Views 15 Replies 11 Participants Last post by  indebt
I'm looking for a method to force the muffler butterfly valves closed even while in Sport / Performance / Track mode. I've read the threads on pulling the fuse to force it always open, but that doesn't work to keep them always closed.

I've got longtubes / cam / whipple, and would like the option to keep the sleeper disguise. ;)
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Somebody recently came up with a board and shared parts list and assembly instruction. Perhaps someone following it can chime in. 15 here so not in my scope of thing to do.
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Interesting idea and I thought of it a while back. With everything going through the computers, I wasn’t sure it was possible. If the valve(s) also affect back pressure, then it could theoretically change things elsewhere. 🤷‍♂️
My car lost about 20whp on a dyno with the mufflers in Tour mode so it's safe to assume there's a horsepower impact. The difference was mostly above 4k, which probably means the open side flows better!
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Found it...!


I'm looking for a method to force the muffler butterfly valves closed even while in Sport / Performance / Track mode. I've read the threads on pulling the fuse to force it always open, but that doesn't work to keep them always closed.

I've got longtubes / cam / whipple, and would like the option to keep the sleeper disguise. ;)
out of curiosity why do you want to force them closed?
My car lost about 20whp on a dyno with the mufflers in Tour mode so it's safe to assume there's a horsepower impact. The difference was mostly above 4k, which probably means the open side flows better!
No doubt the open side flows better, but I'd never have expected a 20whp difference...how modded are you?
out of curiosity why do you want to force them closed?
Not OP but for me, I would like the ability to keep the suspension and steering in performance mode all of the time but still have flexibility to change the exhaust note. I like the valves open most of the time but certain situations like my driveway/neighborhood or cruising in 6th gear on the interstate, I’d like to shut the valves without having to switch the suspension mode. I really cannot stand the feel of the suspension in tour mode… in any driving conditions. Car feels like a land yacht.
if you are tuned, you can do it thru HP tuners. It is in the FPCM. I currently have mine closed on my track setting. That way I can make nefarious trips to Mexico without drawing undo attention to my jackassery.
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No doubt the open side flows better, but I'd never have expected a 20whp difference...how modded are you?
Rotofab, otherwise stock, on a Dynapack. 370whp first pull, 367 second pull, 350 3rd in Tour mode. There probably wasn't enough cooling between pulls, but it still looks like the exhaust or drive mode matters.
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out of curiosity why do you want to force them closed?
My car (2017 6M) has a few mods (ARH longtubes, BTR Stage 3 PD cam, Whipple), so it's really loud with the baffles open. I'd like the option for stiffer suspension and heavier steering all the time, and only sounding hyper aggressive when I want.
Found it...!

Thank you! I'll go check this out.
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You can probably unplug the factory harness from the mufflers and install this module to achieve the option you're looking for. They offer both remote controlled or hard switch option for how you want to open/close the valves. I ordered their remote option for my 2015 to install 2017 bimodal mufflers, the quality looks well built with OEM harness connections to the bimodal mufflers but I have yet to install. Ships from down under and took about 10 days to get here to the states.
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I got the pcb's in the mail last week. I just haven't had a chance to assemble one. The code you need for Arduino is on Thingiverse under the print files, for some reason it won't let me post it here. I think it thinks it's part of a website or something....

I'll update as soon as I get one built and installed.
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if you are tuned, you can do it thru HP tuners. It is in the FPCM. I currently have mine closed on my track setting. That way I can make nefarious trips to Mexico without drawing undo attention to my jackassery.
I did not know that would be available in HPTuners settings! I might have to tinker with that so I can keep it quiet while the wife and baby are in the car without the dynamic drawbacks of tour mode.
I did not know that would be available in HPTuners settings! I might have to tinker with that so I can keep it quiet while the wife and baby are in the car without the dynamic drawbacks of tour mode.
Mode 0-3 corresponds to Tour-Sport-Perf-Track. Change the values in which S-P-T to match Tour and you are good to go. You can even play around with the RPM and gear threshold if you want.
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