Muffler placement affect on sound
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  1. #1
    FST Member Bigmike7645's Avatar
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    Muffler placement affect on sound

    I'm looking at doing an exhaust for my car soon and will likely build it myself. I come from the world of big inch v8's. By that, I mean the last engine I built was a 705 ci Chevrolet for my buddy's grudge race car. That said, i have a hard time finding a sound I truly like on an in line engine (save for an rb26). I know that max power is made with the mufflers as far back as possible due to thermal losses and the slower moving exhaust, but I'm not looking at that last 1/4 hp being the difference in winning or losing. I'm looking for sound quality on this.
    We basically have 3 locations for mufflers on our cars, right after the dp, right before the bend to the axle, and post axle. Can anybody tell me what affect moving the muffler to each of those locations would have on sound? Is one position more prone to popping and crackling? That kind of thing.

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    FST Senior Member ClarkRU's Avatar
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    I can't really comment on muffler placement - all I can say is that my background is just like yours - grew up working on SBC/BBC engines and while I love this car, I have yet after 2 years to find an exhaust setup that makes this car sound anything other than a weedwhacker. I'm curious to see what the results of messing around with muffler placement yields you, as anything other than the stock location is something I haven't heard in this car yet.
    2015 ST3
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    FST Member Bigmike7645's Avatar
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    Most of that brappy rasp comes from the sudden expansion of the gasses to atmosphere. To reduce that, an expansion chamber is required, usually in the form of a chambered muffler of sorts. I've been looking hard at something along the lines of a gibson super flow or mwa as it is a straight through resonator with an expansion chamber.

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    FST Senior Member ClarkRU's Avatar
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    So chambered muffler off the DP with longer tubes = less raspy and more bass-y?

    In my case, I chopped off the resonator and put in a chambered muffler. I still have the stock muffler on though. It's a good balance between stock and having it sound a little throaty, but it would be awesome if it had more growl and didn't sound brappy.
    2015 ST3
    GTX2867R .86ar Big Turbo running Stratified Custom CornTune on AP3 through SpeedPerformance Aux Fuel Kit
    Steeda Intercooler
    Depo Catted DP w/ Ollie's Resonator Delete
    Tial BOV and EWG
    MFactory LSD and ACT Clutch and Flywheel

    JBR Intake
    JBR Cold Side Charge Pipe Kit
    Cobb Filter
    Thermal Zero Turbo Blanket

    Damond Upper Mount
    Cobb RMM
    TB Performance Traction Bar
    Stock All-Weather Tires

  6. #5
    FST Member Bigmike7645's Avatar
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    Quote Originally Posted by ClarkRU View Post
    So chambered muffler off the DP with longer tubes = less raspy and more bass-y?
    The location part is what I'm trying to wrap my mind around.

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    I spend too much of my life on FST! wheelhopper's Avatar
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    Hopefully I'll be able to give you some insight soon on how the Magnaflow exhaust sounds when a muffler is added to the back of the exhaust. I like the Magnaflow, which has a straight through muffler before the rear axle and a resonator just after the DP. FYI the Magnaflow muffler and resonator look the exact same to me, a 5" round straight through design with a louvered tube going through the middle. I like the sound at idle and cruising. During acceleration it has a pitch/tone that is on the verge of ringing your ears, not pleasant. I am hoping if I add a muffler to the back it will eliminate that. I am looking at chambered type. I figure a straight through design will just do the same thing the other 2 are already doing. I am looking at the Dynomax VT, Dynomax Super Turbo, or a magnaflow chambered muffler.
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    FST Member Bigmike7645's Avatar
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    That's the trend I've been noticing is that a lot of the systems place everything pre-axle. I'm thinking the exhaust is still too fast and hot at that point for the mufflers to effectively remove what I find unpleasant in the exhaust note. If I'm right, the couple of bends and direction changes required to run a rear muffler will have slowed the exhaust enough for a chambered type muffler to really mellow out the tone.
    I agree that adding another straight muffler/resonator isn't going to change anything but volume.

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    FST Member Bigmike7645's Avatar
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    I'll be working on the road the next few weeks, so there won't be much progress on this for a bit. It will, however, give me some extra play money to go ahead and order my bend kit, several mufflers, and resonators so I can get to work on this.
    The plan right now is to remove the resonator, muffler, and replace the necked down section between the resonator and axle with 2.5" tubing so the sizes are uniform. Then place various combinations of sound control along the exhaust and observe the changes in sound and drone.
    Can anybody chime in with what types of mufflers are used in the various cbe's offered for our cars? Ie brand x uses 2 straight through resonators, and y uses a chambered muffler and a straight through resonator.

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    FST Senior Member ClarkRU's Avatar
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    Quote Originally Posted by Bigmike7645 View Post
    I'll be working on the road the next few weeks, so there won't be much progress on this for a bit. It will, however, give me some extra play money to go ahead and order my bend kit, several mufflers, and resonators so I can get to work on this.
    The plan right now is to remove the resonator, muffler, and replace the necked down section between the resonator and axle with 2.5" tubing so the sizes are uniform. Then place various combinations of sound control along the exhaust and observe the changes in sound and drone.
    Can anybody chime in with what types of mufflers are used in the various cbe's offered for our cars? Ie brand x uses 2 straight through resonators, and y uses a chambered muffler and a straight through resonator.
    Can't speak for specific CBE designs since I'm effectively running stock, just with Ollies resonator, but I hope to see some results and sound clips of anything you come up with. If you could engineer a different type of exhaust note on this platform, there'd be money to be made...At least in my opinion. All the bolt in options sound relatively the same to me.

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    Finally got around to messing with this some. As of right now the sound comessage from a green filter in an rs box, constant sound symposer (butterfly removed), plm catless dp with 2.5" reducer, 2.25" resonator delete, stock muffler with tip extended 1.875"(top edge of tip is now flush with edge of bumper cover, mostly cosmetic, but actually pulled some mid rpm resonance out of the cabin). I couldn't be happier with the in cabin sound. I get the spool whistle through both ends now! The exhaust cannot be heard over the symposer during light throttle/0 boost until around 3500-4000. Under boost/heavy throttle, the combination of symposer and exhaust gives a very exotic european sound in the cabin. Never overbearing, not too much bass, not to much rasp, 0 drone, 0 popping! That said, I have no idea what it sounds like outside, it might sound like a pulpwood truck with a blown out cherry bomb and a rod knock, but I couldn't care less because it sounds like mechanical sex inside, and that's where I'm always at!
    It's often better to remain silent and appear ignorant than to speak and remove all doubt...

    2016 shadow black st3
    Green filter - butterfly removed from symposer- rs airbox - depo 5.5 fmic -plm catless downpipe with 2.5" reducer & vms j defouler- resonator delete - urethane filled side mounts- diy semi solid rmm- unleashed tune by Torrie- oe tip extended 1 7/8" - Jbr shift arm- energy suspension rear sway bar bushings -matte black dipped snowflakes- ares fitted floormats

 

 
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