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Offline iBuchon

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A baffling problem
on: May 30, 2020, 12:27:30 AM
Iím on a mission to figure out how to make a quieter exhaust that looks better than stock. Hereís my plan.
Keep the stock headers and cat.
Replace the premuffler (breadbox) with a midpipe and use a generic muffler.
Use different baffles in different amounts and  locations.
The generic muffler is solely because Iím going to make a quad muffler this winter and basically just want to test out how to best quiet it down.

Iím going to try to document every step and share what the differences are. Video doesn't do motorcycle exhaust sound justice as we all know, but Iíll do my best.

These are the parts Iím using:

eBay midpipe

There are several options here. Some come with mounts for the stock exhaust cover and/or parts to weld your stock premuffler back on.

eBay muffler:


eBay baffle:

FMF fiberglass packing:


Video 1. Removal of premuffler and testing different single baffle locations.

No baffle was obviously very loud. The power wasnít noticeably different, but the delivery seems less linear and the throttle input seems more abrupt. Good times for short periods for me personally, but Iím in search of a quieter option.

The baffle inserted into the muffler didnít have much of an effect on noise or power compared to no baffle. It did take off a couple decibels at idle but sounded louder while riding in the mid rpm range to me. It did take some of the off throttle popping down a notch too.

Putting the baffle in the midpipe was very quiet, but way too restrictive! It wasnít designed or advertised to be used there. The Z lost power everywhere. No power wheelies and after 5k it revved out very slowly. It was silky smooth with throttle input though. I imagine this is what a restricted motorcycle would feel like. Surprisingly, it didnít throw any codes.

Drilling out the baffle as seen in the video returned the power. This is quieter than the muffler baffle option and felt most like the bike did with the stock premuffler. The riding ďtestsĒ were pretty much identical if not better than the other options that didnít impact power. I might even conclude that this option has more middle range power than the other two with a comparable top end.

EDIT: The above was not actually true. I discovered later that the packing had blown out because I made it thinner to fit more easily. Iíll have the update in another video/post.

Last Edit: May 30, 2020, 12:29:18 AM by iBuchon

Online cjskinner

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Re: A baffling problem
Reply #1 on: May 30, 2020, 12:36:57 AM
Looks like you had fun during the covid! That's the sad part of the z900. It's 2 extreme, loud or quiet.

Are you going to try with a longer can with an integrated baffle?
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Offline Cazzy_R

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Re: A baffling problem
Reply #2 on: May 30, 2020, 01:36:47 AM
Strangling flow to quieten down a short exhaust won't work without also strangling performance.
If you look at the internals of the standard breadbox and muffler the exhaust gases are not forced through any small holes.
Kawasaki use relatively large bore perforated pipe surrounded in wadding exiting into expansion areas where the exhaust flow is slowed down. turned around and routed out along another perforated pipe in the opposite direction. If you straightened out those pipes from the breadbox and end can they would extend out beyond the back wheel.
This obviously means that the exhaust gases are in contact with a much larger surface area of wadding than any aftermarket can. The standard exhaust is quiet and heavy but it isn't as restrictive as people think and it probably less restrictive than some corked (baffled) aftermarket cans.

 iBuchon if you are going for a 4 outlet system I would concentrate on the potentially large absorption area of those 4 outlet pipes.
4 x 25mm dia outlets will equal the cross sectional area of one 50mm outlet and give you the opportunity to wrap the last 200mm or more of each outlet stub in wadding without restricting flow. The more of the exhaust gases you can bring into contact with the wadding the quieter it will be.
 If you find a satisfactory noise/performance balance with your current single outlet it probably won't be the best solution for the 4 outlet arrangement though I am enjoying watch you try. Nice video.  :821:

P.S. I don't think the catalysts quieten the exhaust as much as people think either.

Tighten it 'til it strips then back it off half a turn.

Online Swingin Spanners

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Re: A baffling problem
Reply #3 on: May 30, 2020, 06:29:52 AM
Have you considered using the bread box as a manifold to connect the dual outlets?

The internal structure of the bread box is all wrong for your purposes, but if you move some of the baffling around in the bread box it might work really well so your tailpipes x4 can be straight through.

I've chopped up an OEM muffler on my FZ6 with good results that were a bit of a bark without being ridiculously loud. I just changed the baffles around and welded the box back together. It was all hidden under the seat.

Offline iBuchon

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Re: A baffling problem
Reply #4 on: May 30, 2020, 03:13:15 PM
Thanks for the input from all. I do realize that with the stock breadbox itís not very restricted, just redirected basically. I actually love the sound of the 8$ exhaust and only moved on from it because I wanted to try something different and experiment with different setups. The large volume is likely the only way to achieve the sound level and tone that suits my taste.

The quad mufflers will be longer. I havenít decided on diameter yet. Have to get my hands on some old Z1000 mufflers to see what they were because I really liked that size. If you have ever seen them, they do prove you can get a quieter sound out of a baffled pipe setup without a breadbox. They used a similar method on a smaller scale. People used to cut them shorter, but this just randomly shortened a path that was designed to flow a certain way and the sound suffered. Raspy, but not in a pleasing way.

An alternative would be using a breadbox, but making out smaller and more attractive. Sounds counterintuitive, like was mentioned. If nothing else, maybe itíll keep us all entertained.  :152: