DIY Muffler...

[degrom]

Hi all...

What goes into building a muffler?

I am interested in building a one just for interest sake. I know you use exhaust filling to fill it up and that it is basically a cross drilled pipe in an even bigger pipe... LOL

This made me think... Where do you get the cross drilled pipe? Or do they manually drill 5million holes in each pipe?

Any useful facts are welcome.
Cheers.

[imdying]

The inner baffle is a perforated tube, they perforations aren't just holes, but little flow restrictors I guess you'd call them. You can get lengths of it from somewhere like www.autobend.co.nz, or probably better for a welly man, www.neptunemufflers.co.nz. But you're right, they're essentially a baffle, and outer tube, some packing and some flanges

[degrom]

The inner baffle is a perforated tube, they perforations aren't just holes, but little flow restrictors I guess you'd call them. You can get lengths of it from somewhere like www.autobend.co.nz, or probably better for a welly man, www.neptunemufflers.co.nz. But you're right, they're essentially a baffle, and outer tube, some packing and some flanges

Thanks... I sent them a few inquaries.

Will a home made muffler that is under 100db pass a WOF?

Thanks.

[Ixion]

Thanks... I sent them a few inquaries.

Will a home made muffler that is under 100db pass a WOF?

Thanks.

Yes. So long as it is properly attached, cannot easily be dismantled etc. NZ has no homolgation rules

[imdying]

Will a home made muffler that is under 100db pass a WOF?

Of course! Hell, home made fairings, fuel tanks, wheels, brake calipers, and pretty much anything else you can mention will get a WOF It's only things with DOT markings that they get pissy about in NZ, light lenses, tyres, brake hoses... that's about all that comes to mind. NZ is still reasonably liberal in that respect.

I've actually just emailed Neptune a couple of days ago about having a muffler made... I've not heard back yet, will probably make one myself if I don't hear back.

[Motu]

I made my own mufflers for my XLV750 a few years ago - some high tech design I got out of ''Four Stroke Engine Tuning'',or maybe some other tuning book.They used a couple of concentric cones and some Helmholtz chambers,but a few big holes - they were pretty noisey,but not over the top.I dynoed the bike before and after....the previous system was my own too,but pretty open,using 4 hotdogs,2 per side.It took me 2 or 3 weeks to make them,maybe 8 hrs per muffler.I'd like to do it again when I get some time,but this time make them adjustable.I'll upload some photos from my work computer tomorrow.

[degrom]

I made my own mufflers for my XLV750 a few years ago - some high tech design I got out of ''Four Stroke Engine Tuning'',or maybe some other tuning book.They used a couple of concentric cones and some Helmholtz chambers,but a few big holes - they were pretty noisey,but not over the top.I dynoed the bike before and after....the previous system was my own too,but pretty open,using 4 hotdogs,2 per side.It took me 2 or 3 weeks to make them,maybe 8 hrs per muffler.I'd like to do it again when I get some time,but this time make them adjustable.I'll upload some photos from my work computer tomorrow.

The photo's would be greatly appreciated. What did the dyno say about your pipes? Better or worse than the manufacturers ratings?

Thx

[Motu]

I was comparing the mufflers to my previous open system,and there was no difference in power.I have no idea about comparison to the manufacturer's figures as they measure crankshaft hp,I was getting a rear wheel hp reading.

On my first system I had one hotdog coming up parallel with the subframe tubes,and another inside the standard stainless heatshield at the rear,but this system was the same size as the heatshield so couldn't use them.,but they didn't cause a problem,as I seldom carry a pilion.I left the first hotdogs in place.I don't have the book so can't scan a diagram,but inside is a cone with various large holes,and behind are two Helmhotz chambers,the exhaust comes out around the outside.I actualy used an old driveshaft to make the Helmhotz chambers.So nothing too technical,just a lot of cutting and welding.

[degrom]

I was comparing the mufflers to my previous open system,and there was no difference in power.I have no idea about comparison to the manufacturer's figures as they measure crankshaft hp,I was getting a rear wheel hp reading.

On my first system I had one hotdog coming up parallel with the subframe tubes,and another inside the standard stainless heatshield at the rear,but this system was the same size as the heatshield so couldn't use them.,but they didn't cause a problem,as I seldom carry a pilion.I left the first hotdogs in place.I don't have the book so can't scan a diagram,but inside is a cone with various large holes,and behind are two Helmhotz chambers,the exhaust comes out around the outside.I actualy used an old driveshaft to make the Helmhotz chambers.So nothing too technical,just a lot of cutting and welding.

Nice!!! Thanks for the cool pictures!!!

What did you do for paint? Did you need to bake the heat paint and is it still looking okay after a few km's?

Thanks again!!!

[Motu]

Just heat proof exhaust paint,I had the headers ceramic coated.The paint was still perfect after 4 years before I sold it.

[degrom]

Just heat proof exhaust paint,I had the headers ceramic coated.The paint was still perfect after 4 years before I sold it.

Cool!!!

What is involved in ceramic coating and was it expensive?

[Motu]

The pipes have to be able to stand up to a sand blasting inside and out,cost me me $100 I think.I used HPC because the owner bought my old 'Coon.

[geoffm]

If you want to design the exhaust system scietifically (at least for noise) look up a program called "Silencer" for designing the Helmholtz chamber sizes.
I have bought the perforated tube from Papakura Engineering (Auck) in the past. I have some if you need a piece - depends what size you want. For my GSXR muffler, I packed the core with fiberglass mat and chopped strand, and taped around the outside to pull the fiberglass in tight so it would fit in the outer tube.
I am planning on making some 2 stroke pipes for the RD some day, since the bought ones "could be better".

[AllanB]

I purchased a pair of aftermarket mufflers for my old 750 twin that had a perforated core system (straight through) that were too loud. I got a bit of muffler pipe and cut slots in in and punched them inward to make a pair of insert baffles as per attached photo. They knocked down the sound a lot (the first set too much so I made a shorter set). I noticed no difference at all in performance with or without them. The theory is that they disturb the flow a bit while still being a 'performance' baffle. Should look like a set of 'hills' when looking from the direction of flow -engine end (not 'caves').
If yours is a bit loud whip up one of these for inserting in the end.

[The Pastor]

are they just a friction fit in your muffler?