Two Brother's Exhaust Sylencer Mod

[avogt18]

Originally Posted by Parabellum

Thread bump for this awesome mod.

I just got my two bros exhaust installed and its just way too frakking loud. I had heard people say it was loud, but I had no idea it was going to make my ears ring after even a 5 minute ride.

yeah its loud, and this mod definatly helps! i loved it after doing this, also quiets idle down a bunch! but some of you know, my fz6 is gone, i havent been posting lately cause i have a 08 600rr now. the fz6 was totaled, and the insurance picked it up, i thought of removing my homemade baffles first, but never got around to it. didnt take the twobros off first eather,cause the insurance paid me in full for the optional parts i had on the bike, wich was awsome!

[hokiekiteboarder]

Originally Posted by avogt18

yeah its loud, and this mod definatly helps! i loved it after doing this, also quiets idle down a bunch! but some of you know, my fz6 is gone, i havent been posting lately cause i have a 08 600rr now. the fz6 was totaled, and the insurance picked it up, i thought of removing my homemade baffles first, but never got around to it. didnt take the twobros off first eather,cause the insurance paid me in full for the optional parts i had on the bike, wich was awsome!

congrats on the 600rr. I just got an '08 grafitti myself a few weeks ago.

I'm keeping the FZ though for longer road trips and will still use it along with the rr for commuting. I had bought the stuff needed to do this mod to my two bro's exhaust a while back - but not gotten around to it. I took an extended road trip last weekend and, while I love the way it sounds, that trip made me realize that I still need to do the mod and will be doing it soon. I think the extra noise actually made the trip more tiring (even with ear plugs).

I've put about 3000 miles on it already. Does anyone that has the two bro's think it is either necessary or worth doing a re-pack since I have to take it off anyway to do the mod?

[Parabellum]

Originally Posted by hokiekiteboarder

congrats on the 600rr. I just got an '08 grafitti myself a few weeks ago.

I'm keeping the FZ though for longer road trips and will still use it along with the rr for commuting. I had bought the stuff needed to do this mod to my two bro's exhaust a while back - but not gotten around to it. I took an extended road trip last weekend and, while I love the way it sounds, that trip made me realize that I still need to do the mod and will be doing it soon. I think the extra noise actually made the trip more tiring (even with ear plugs).

I've put about 3000 miles on it already. Does anyone that has the two bro's think it is either necessary or worth doing a re-pack since I have to take it off anyway to do the mod?

I think its too early to need a repack. I know a lot of guys who have put as much as 10K miles on their exhausts before a repack was necessary.

So here is my plan, I got the materials last night and I am going to operate in reverse of what the OP did. I am going to start with a restrictor (7/8" ID) placed near the tips of the exhaust (I have the db killer power tips, so it will work in conjunction with them) and see how that changes the sound levels.

If that alone isn't enough, then I will take the cans completely off so I can put the same plates in the rear of the cans.

I am not looking to cut 10db here....I would be perfectly happy to lose 5-6db.

[hokiekiteboarder]

Originally Posted by Parabellum

I think its too early to need a repack. I know a lot of guys who have put as much as 10K miles on their exhausts before a repack was necessary.

So here is my plan, I got the materials last night and I am going to operate in reverse of what the OP did. I am going to start with a restrictor (7/8" ID) placed near the tips of the exhaust (I have the db killer power tips, so it will work in conjunction with them) and see how that changes the sound levels.

If that alone isn't enough, then I will take the cans completely off so I can put the same plates in the rear of the cans.

I am not looking to cut 10db here....I would be perfectly happy to lose 5-6db.

Great, please post some pics when you're done. I have the power tips as well and I hadn't thought of doing it in reverse. That probably would be easier to do. Truthfully, i didn't notice much difference with the 1-3db reduction from the power tips alone.

[Parabellum]

Originally Posted by hokiekiteboarder

Great, please post some pics when you're done. I have the power tips as well and I hadn't thought of doing it in reverse. That probably would be easier to do. Truthfully, i didn't notice much difference with the 1-3db reduction from the power tips alone.

The power tips don't do squat except for looking really nice.

3db is half the volume (in SPLs)....if the power tips actually took off 3db, they would be worth the money.

I have the tips because they came with the exhaust (bought second hand from an SBN member)...I would not have paid for them otherwise.

My current design (which I will fab and install tonight) is to use 0.025" aluminum for the restrictors. They will be set into the same recession as the tips, between the tip and the end of the muffler. I am going to start with a 7/8" hole in the center of the restrictor and if that is too much, I will expand it to be 1".

I'll report back on how it sounds at every stage of this project, as I suspect I am not the only person who loves the Two Bros but wishes they were about 6db quieter.

[Parabellum]

Ok guys, got the restrictor plates fabricated last night and I have results to report.

Two Brothers restrictor plate design: Two 0.025" thick aluminum plates with an OD just under 2.25" (to fit in the recession for the power tips) and an ID of 7/8". Painted flat black with high temp (1200f) grill paint. Installed between the end plate of the cans and the magnesium tips, under the db killer "power tips".

Results: The results are actually quite amazing. These plates, when placed in the endcaps behind the power tips reduce the exhaust noise to OEM sound levels. Its like a totally different exhaust.

1100-4000Krpm = Sound is low and throaty, similar to the original Two Bros sound.

4000K-Redline = Sound is identical to the OEM muffler.

Power gains: All power gains of the two bros exhaust are totally negated by this mod. The large bump in power above 8K is totally gone.

Next step: The next step is to incrementally widen the ID of the plates until I get what I am looking for. This set of plates was a successful proof of concept, and now I just need to find the right ID for the sound I want. I am going to widen the ID to 1" and see how that goes, then I will repeat the process until I find something suitable.


So....I am pleased to report that this mod was both a success and a failure.

Success - This mod will make the exhaust street legal (as far as noise goes). You should NOT attract any unwanted attention with this mod in place.

Failure - Takes all the fun out of the exhaust. Why pay big $$$ for this exhaust and then make it sound like OEM? Plus, you lose all the power gains too.



Final results: I built these plates, but removed them after the long test ride. I will keep them, just in case I get a fix-it ticket...but for now I am going to rock this exhaust with the power tips and live with the noise level.

I think the fact that I have a DEAD quiet car (2003 BMW 3 series with oem exhaust) and previous to this, had a dead quiet bike (Stock FZ6) had made me forget what a real bike is supposed to sound like.

Every day I ride with these pipes, I get more used to the noise level.

I asked my neighbors about the sound of the bike and they said that it wasn't a bother to them at all.

[hokiekiteboarder]

Thanks for the update. I honestly didn't notice a power increase when I put the two bro's on in the first place. That is just my perception, not from a dyno run. Maybe I would notice it if I went back to stock, but I don't think it would bother me that much. I am going to give it a go but with a larger ID - hopefully this weekend but probably not until next. I'm like you in that I don't need to knock the noise down that much, but I do want to take the edge off a little bit hopefully without changing the great tone that these pipes have.

[Parabellum]

Originally Posted by hokiekiteboarder

Thanks for the update. I honestly didn't notice a power increase when I put the two bro's on in the first place. That is just my perception, not from a dyno run. Maybe I would notice it if I went back to stock, but I don't think it would bother me that much. I am going to give it a go but with a larger ID - hopefully this weekend but probably not until next. I'm like you in that I don't need to knock the noise down that much, but I do want to take the edge off a little bit hopefully without changing the great tone that these pipes have.

If you come up with a solution for drilling a 1"+ hole in that plate without paying $50 for a large unibit...please let me know.

I insist that this mod look factory...so the hole has to be *perfectly* round and centered....and so I refuse to try and grind it out with a dremel.

My problem now is that my unibit is 7/8" max diameter...so I have no tool for cutting a perfect 1"+ hole in the aluminum.

[hot4teach2]

Originally Posted by Parabellum

The power tips don't do squat except for looking really nice.

3db is half the volume (in SPLs)....if the power tips actually took off 3db, they would be worth the money.

3db is not half the volume. 10db is. For instance 90db is twice as loud as 80db. It is said that 3db just noticeable, but that is argued.

[hokiekiteboarder]

Originally Posted by Parabellum

If you come up with a solution for drilling a 1"+ hole in that plate without paying $50 for a large unibit...please let me know.

I insist that this mod look factory...so the hole has to be *perfectly* round and centered....and so I refuse to try and grind it out with a dremel.

My problem now is that my unibit is 7/8" max diameter...so I have no tool for cutting a perfect 1"+ hole in the aluminum.

I went to Lowe's and bought a 1" hole saw bit (the type used for cutting the hole a door for door knob/latch set - only smaller) for around $4 - They had multiple sizes to choose from. It says on the packaging that it is for wood and metal. I don't know for sure if it will cut a smooth hole or not but if it doesn't work, the aluminum is cheap enough to replace and try something else.

The pattern for the inserts will be drawn on the sheet of aluminum from a paper template (avogt18 gave me that idea), My plan is to tack the solid piece of aluminum to a scrap piece of 2 x 6 to anchor it while I drill out the center hole. Afterward I would cut out the rest of the insert around the outside diameter with some heavy aluminum shears. If the outside cut ends up being a little rough, I can smooth it some with the dremel. I hope to try it this coming weekend as I have 3 days off to mess with it.

[SovietRobot]

Originally Posted by Parabellum

Thread bump for this awesome mod.

I just got my two bros exhaust installed and its just way too frakking loud. I had heard people say it was loud, but I had no idea it was going to make my ears ring after even a 5 minute ride.

The whole point of a motorcycle is to have loud pipes.

You can tell it to any cop: It's a safety feature.

[ltdan]

Maybe it's the fact that I drive a straight piped diesel truck, or maybe it's the fact that I have a single side exit TB from an R6, but I don't think they are loud at all, I actually think it's pretty tame for the most part until you really rev it.

[Parabellum]

Originally Posted by hot4teach2

3db is not half the volume. 10db is. For instance 90db is twice as loud as 80db. It is said that 3db just noticeable, but that is argued.

You are wrong, go check on the dB scale for sound pressure levels and get back to me.

3dB = 100% increase/decrease in SPL.

I started my education in Acoustics and finished it in Digital Signal Processing, I know what I'm talking about here.

[Parabellum]

UPDATE: I used my spindle sander to enlarge the holes in the restrictor plates (see my post above for details) to 1.25"....which seems to be the perfect size.

From 0-4K its low, throaty growl is great.

Above 4K it sounds more like the stock exhaust: It screams, but its just toned down enough to make the sound NOT ear splitting.

I'll be sticking with this design as final: Interior diameter of 1.25" for the plates.

[hokiekiteboarder]

Sounds exactly like what I am looking for - hope to give it a go this weekend. Just have to get some high temp paint.