I've been wanting to build a muffler with a butterfly in it that allows straight thru when open and triple flow when shut. I kicked the idea round with a few mates an beers and this is the result. 3" straight thru or 1 3/4" triple flow. Seems to work alright, nice an quiet in "sneaky" mode, not that loud straight thru. Still makes good boost, but the microleb runs things a bit Ritch up top when in quiet mode.
That's pretty awesome!, did you just fill it up with steel wool, where say, tenneco would use fibreglass?
Could you make it automatic? I mean find a way to hook-up something like an extra output from the ECU ... ?
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Nah I used ss wool for most of it with some glass fibre in the second section of skinny pipe to remove some extra top end. That said the ss wool works pretty well, I've got 3 straight thrus on a 3" system and she's pretty quiet (ish)Originally Posted by niggerjewz
Yeah you could set it up as an active exhaust, but with the microleb I'm running being map sensor driven, the V/E changes with different amounts of back pressure ie exhaust butterfly angle. This means it runs rich up top with it in quiet mode unless you adjust the mixtures on the Ecu up top. You could probably tune around it if its actuator is controlled relative to MAP.
my mate ran a boost line to a big throttle body in his muffler to do an automatic style open up the loud straight through section when on boost.
it needed regular cleaning as it would stick was the only issue - probably needed bigger clearance to allow for carbon build up
Exhaust brake butterfly out of a small truck?
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Looks heavy! How does it work again?
this, connected to a small ram fed by boost/vac
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Or a $10 choke cable stuck thru a hole in the floor lol. I mostly only put it in quiet mode to go into town and other places where cops lurk. Been having to use copious lube to move lately, so thinking glenno's idea would have worked better long term.
Its reasonably heavy at about 8kg at a guess it is prototype 1.0 so its made out of whatever's in the shed including but not limited to 25mm rhs cut from the leg of a bench. 8mm plate butterfly notch cut into a half shaft, with a twist! It shuts at 60° and is therefore oval, cut on the lathe bolted to an angled mount. Just bushes top and bottom for the shaft.
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About 8kg
Open its just a 3" straight thru with ss wool packing about a foot long. The butterfly is about 6" in from the inlet.
With the butterfly shut, the gasses pass out of a hole in the side of the pipe just before the butterfly. This hole leads to the 1st resonant chamber and small straight thru muffler, leading to a larger resonant chamber with damping ( read as ss swarf off the lathe). The gasses pass from here to another small straight thru with fiberglass & ss packing before exiting at another chamber and out a hole after the butterfly. Having now done a lap of the muffler down one side across the back of the muffler and up the other side to empty out after the butterfly and exiting thru the 3" in the middle.
this makes it sound like a 3" system even in quiet mode!
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