Project: Performance Muffler from scratch

Ive been wanting a new higher flow muffler for my Honda Gx390 on my wheelhorse. this muffler idea could be used for about any motor out there. Ive never tryed it before but flowmaster uses a somewhat similar idea to lower the volume without packing. ON TO THE PICS!
first punch out some disks


Then arrange them on a 1/4 inch rod



Then stick that inside this piece of 3 inch tubing



then the basic idea is that you have endcaps that the rod gets welded to on either end and obviously the disks all get welded to the rod before hand. the disks have a air gap of about 3/8 to half inch all the way around. anybody a muffler guru around here that can give me some tips comments or concerns? let me hear them !

Thats basically the same thung as a gun suppressor, just the airflow goes on the outside of the baffles instead of through the center. Either way really cool.

Doug Fackler wrote:

Thats basically the same thung as a gun suppressor, just the airflow goes on the outside of the baffles instead of through the center. Either way really cool.

That's what I was thinking! It's a pistol silencer made for an engine lol! I bet it would work well.  

Any updates on this muffler?   

thats funny you guys caught on to the basis for the idea so quickly, Lets just say I also like my guns alot... I figured if it works for a gun should work for a mower... No updates till thursday as that will be the next chance I get to work on it, tomorrow my Carport Im converting into a garage is coming     and I work 24 hours wendsday,

Dang im curious as to how it sounds. Do you work at that shop? looks to be a machine shop almost, awesome tools.   

Creepycrawler wrote:

thats funny you guys caught on to the basis for the idea so quickly, Lets just say I also like my guns alot... I figured if it works for a gun should work for a mower...  No updates till thursday as that will be the next chance I get to work on it, tomorrow my Carport Im converting into a garage is coming     and I work 24 hours wendsday,

a silencer is a silencer... expanding gases make noise. The only thing I'd change would be to make the bends step around in a spiral... this would make the gases travel a longer path, and create a vortex cancelling out the backpressure from the baffles

It should have different degree bends or size. Looks good tho.

ok thanks for the Input, Ill spiral the disks, and I have a idea for changing the flow a bit. to hard to explain in words, Ill get some pics of it thursday

Red, I dont "work" there, its the shop at my dads house, where I wrenched for past 15 or so years (lived at home, started wrenching in there when I was around 10) I just bought my own house, and dont have a garage yet, So Im still doing all my wrenching and fabbing there. It is a machine shop, thats the fullsize bridgeport Knock off in the picture, and it has a Large metal lathe with around a 24 inch throw and around a 3ft bed. I can use it whenever I feel like it. Im very lucky to have such a nice place to "play"   

That sorta resembles a Supertrapp.

How does it sound???

Ok so I got alot done on this yesterday, just have to get bolts to bolt it to the engine and build the muffler mounts down on the frame so it doesnt over stress my exaust mounts on the motor if a stick hits it or something. first off Im a little disappointed, its louder than I would like. much more quite than no muffler but significantly louder than the factory muffler. I was going for closer to factory muffler quietness. So Im still on the lookout for a honda xr muffler Like the other guys run. or maybe Ill get real motivated and try again with another muffler. Either way enough jabbering on to the pics!

First is the additional supports/baffles I put in the system right after I cut them out.



big middle baffle welding in place



I then stacked two of the disks that I made a couple days ago in, and welded them in place. then the smaller baffle got installed and welded in. then two more round baffles welded and repeat for the other side. This pics shows about halfway through the process



then made a endcap and welded it on



then built a endcap for the other side, and at this point my phone died so I couldnt get pictures of the finished product    but it came out nice, Ill grab a couple finished pics today. this could be all in my head but the motor does seem to rev a touch quicker, mabe from less backpressure? not sure, I wont get a chance to test it till it warms up around here, the high for today is 16 here and it is 1 F right now.

Nice work! Let's hear it! Can you take a vid when it warms up out there?

I surely will, I wish I would have taken a "before" video for direct comparison, but oh well. Its suppose to be decent sunday, maybe I can grab a vid then.

That's a great idea to have a comparison vid. I'm planning on doing a similar thread on an exhaust for my Murray. I'll have to do a vid on the stocker before I build a system.

What does your system look like installed? Did you paint it? I've had good luck with VHT brand paint for exhausts.   

Looks great, can't wait to hear it. - Make sure you mount that thing properly, cause it looks kinda lethal heavy'ish   

If you cut it back apart and wrap FMF exhaust packing around it, it will be much quieter.

Well good and bad news... Good news I got pictures of the finished exhaust, bad news no video... because of broken head studs.
Tdub, Im going to use that paint you recommended, Hope it holds up good,
Thunder, its very lethal heavy lol It will be fully supported by the frame, the mounting flange will just seal the system to the head.
Pony, I dont think that will work for this design, but I think Im gonna build a new muffler part at some point that I can use packing in.
Ill let the pics do the rest of the talking, first up completed muffler


Dam broken studs


had to pull the head, Ill put up more pics when I get it fixed, I need a new head gasket now

fixed, drilled the old bolts out on the mill and retapped to NC 5/16 picking a head gasket up tomorrow and hopefully riding sunday

I love how ya show the good, the bad, AND the ugly in your thread. Some Posts are simply "Braggarts builds".... They had all kinds of problems, but never mentioned them in the write up. We don't get that much here on this site, which is why this place is so conducive to learning. I honestly believe we learn more from seein "what didn't work" than form the solution. Good work brother, lookin forward to more installments.

Lawren Wimberly wrote:

I love how ya show the good, the bad, AND the ugly in your thread. Some Posts are simply "Braggarts builds".... They had all kinds of problems, but never mentioned them in the write up. We don't get that much here on this site, which is why this place is so conducive to learning. I honestly believe we learn more from seein "what didn't work" than form the solution. Good work brother, lookin forward to more installments.

You're absolutely right. We learn from our mistakes, and learning from somebody else's mistakes is a very valuable asset, too. Creepy- you got some good work going on there. Muffler looks very neat, can't wait to hear it.

Some of us don't make any mistakes...   

There are no mistakes... Just a lot of "Design Modifications"

I prefer to call it tweaking...

When things don't go as planned, I quickly revert to HACK MODE lol!  But things still go together, just not as pretty as planned. (see my exhaust thread: A hammer was never a planned tool but usually enters into the equation at somne point)    

Great thread BTW

Creepycrawler wrote:

Well good and bad news... Good news I got pictures of the finished exhaust, bad news no video... because of broken head studs.
Tdub, Im going to use that paint you recommended, Hope it holds up good,
Thunder, its very lethal heavy lol It will be fully supported by the frame, the mounting flange will just seal the system to the head.
Pony, I dont think that will work for this design, but I think Im gonna build a new muffler part at some point that I can use packing in.
Ill let the pics do the rest of the talking, first up completed muffler


Dam broken studs


had to pull the head, Ill put up more pics when I get it fixed, I need a new head gasket now

Looks great! - And about the video Q,- Make sure it has Stereo sound.