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degrom
20th September 2006, 22:34
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
20th September 2006, 22:46
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
20th September 2006, 22:57
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
20th September 2006, 23:00
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
20th September 2006, 23:00
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 :yes: 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
20th September 2006, 23:29
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
21st September 2006, 06:49
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
21st September 2006, 09:02
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
21st September 2006, 09:39
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
21st September 2006, 10:11
Just heat proof exhaust paint,I had the headers ceramic coated.The paint was still perfect after 4 years before I sold it.

degrom
21st September 2006, 12:11
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
21st September 2006, 12:27
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
21st September 2006, 20:49
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
9th October 2006, 20:42
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
9th October 2006, 21:07
are they just a friction fit in your muffler?

TLDV8
9th October 2006, 21:07
There is also carbon tube available.
I think the tube i used was made in Rotorua,but there is also this place in Auckland.
The resin was strong enough to be able to turn the tube ends in the lathe.

http://www.carbon-tube.com/index.php

.

SARGE
9th October 2006, 21:19
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 :)

mufflers have packing ????? :gob:

imdying
10th October 2006, 07:12
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.

Thanks for that mate, I might need something like that for warrants....


So, an update. Made my first cardboard 1:1 model last night and fitted it. Was a bit tight, have a revised edition coming tonight. Think I'm going to go for a single outlet instead of twin outlet though, just to get the volume in silencing material :/ More research!

MSTRS
10th October 2006, 08:26
...., 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.


Good point here - packing should be reasonably loose, and certainly not wrapped tight on the perforated tube. What you are trying to achieve is exhaust flow essentially going straight through, but the sound waves expanding in the muffler by going through the holes at the 'front' of the perf.tube, filtering through the packing (which is why it should be fairly loose/uncompressed) then re-entering the perf. tube towards the rear and then exiting the whole system.
This is essentially the 'Coby' design (what the Americans call a glass-pack). If you get it right, you will achieve enhanced performance with an acceptable dB

imdying
10th October 2006, 17:37
There is also carbon tube available.
I think the tube i used was made in Rotorua,but there is also this place in Auckland.
The resin was strong enough to be able to turn the tube ends in the lathe.

http://www.carbon-tube.com/index.php

.

You bastard, stop showing me that shit :spanking: :2thumbsup

R6_kid
10th October 2006, 17:53
mufflers have packing ????? :gob:

i thought thats what dover did when you left your bike unattended in his presence.




Whats a good thickness of carbon-fibre to use for and exhaust? I've finally devised a cheapish way to get an M1R replica pipe made with no hassle, but no really sure whats a suitable thickness of carbon to use.

AllanB
10th October 2006, 18:02
Yep - slid inside the existing pipe and I held them in with a stainless steel seft tapper. I'd also welded a bit of rod in the centre to grab onto to make removing easier but this is not essential.

degrom
10th October 2006, 19:18
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.

LOL.. It might just help me get my wof in the future with all the noise restrictions.

Thanks for the tip!!!