I wonder what sort of muffler the Mazda Rotary cars had? I know I have read that the rotary is a real noise maker when unmuffled. I think there was an article about someone running a rotary on the salt without any muffler and the comments about the amount of noise it made.
Randy -----Original Message----- From: mercedes-boun...@okiebenz.com [mailto:mercedes-boun...@okiebenz.com]on Behalf Of Barry Stark Sent: Monday, January 18, 2010 2:13 PM To: 'Mercedes Discussion List' Subject: Re: [MBZ] OT: Muffler design? Randy - Hey, I did say it would burn out over time. Actually when I have seen that used in the past, it was the real coarse stuff not the hair fine stuff. The fine stuff doesnt work as well as the coarse stiff anyway as it just seems to block the exhaust flow where the coarse stuff lets the sound get trapped in it and bounce around thereby robbing the sound pulse of its' energy. Also the silencer with the steel wool located was at the end of the "stinger" on the expansion chamber. The temperature at that point is quite a bit lower than the "fire" coming out of the exhaust port. Curt - In your situation, I'm guessing that the muffler may be rather close to the exhaust port. The steel, even the coarse stuff may heat up and oxidize rather quickly. I was thinking that maybe you could find a machine shop that is turning some stainless parts on a lathe and retrieve some of those "pigtail" turnings. They may be heavy enough not to heat up as much as fine strand and they would not oxidize as readily as a steel part. Even fiberglass close to the exhaust port would not last long. I imagine that rotary engines have a pretty hot exhaust stream much like a 2 stroke. On a 4 stroke, the exhaust valve ends up taking some of the heat from the exhaust stream and transferring it to the head, so things are a bit cooler. Barry > -----Original Message----- > From: mercedes-boun...@okiebenz.com [mailto:mercedes- > boun...@okiebenz.com] On Behalf Of R A Bennell > Sent: Monday, January 18, 2010 11:34 AM > To: Mercedes Discussion List > Subject: Re: [MBZ] OT: Muffler design? > > I don't think I would use steel wool. It burns. Try it. Even soaking > wet, it will ignite and burn. > > Randy > > -----Original Message----- > From: mercedes-boun...@okiebenz.com > [mailto:mercedes-boun...@okiebenz.com]on Behalf Of Curt Raymond > Sent: Monday, January 18, 2010 11:27 AM > To: Diesel List > Subject: Re: [MBZ] OT: Muffler design? > > > Barry, > > Great info! I knew a little of that but you put it into context. > > My problem is that this is such an oddball machine. '71 Arctic Cat > Panther 303 Rotary... They used the 303 from > '69 through around '72. This was the dawn of race sleds and the 303 was > NOT one of those ;) > > Theres extremely limited space to put the pipe in and any performance > tuning has already been ruined because the > exhaust port faces almost straight down. Theres a pipe from it around > to the front (maybe 12") which then takes a > left turn (the engine is about the same diameter as a 5 gallon bucket > but only about 2/3 as tall. If it were a > bucket it'd be lying on its side in the sled) and enters the "muffler" > which is about the size and shape of a > coffee can in the center of one end of the can. At the other end of the > can another pipe comes out making another > left turn. It goes down about 16" and makes a turn stright down and > out. > > So as you can see this is about the WORST design possible... On a > positive note I don't think a rotary engine > requires much exhaust gas scavenging since the intake and exhaust ports > don't overlap like they do in a piston > engine... > > I like the steel wool idea, I think I'm going to try to end up with a > combo approach, baffles and steel wool... > > -Curt > > Date: Mon, 18 Jan 2010 08:38:04 -0800 > From: "Barry Stark" <barryst...@verizon.net> > To: "'Mercedes Discussion List'" <mercedes@okiebenz.com> > Subject: Re: [MBZ] OT: Muffler design? > Message-ID: <000001ca985c$9c10f290$d432d7...@net> > Content-Type: text/plain; charset=us-ascii > > Curt - > Manfred is correct. The downside of not using a properly designed > exhaust > system is that you may end up with a destructively lean mixture at full > throttle, or you may just have reduced power. While the reduced power > is > likely not a big thing, the excessively lean condition can be. With > whatever > system you end up with be sure to take a spark plug reading after a > short > full power run to determine if the mixture is within range. If it is > just a > bit lean you can likely either adjust the high speed needle valve or > install > a bigger main jet depending on the design of the carburetor. If it > "blubbers" it may be too rich and the appropriate adjustments can be > performed to correct that instance as well. The best system for a 2 > stroke > is what is called an expansion chamber. It consists of a divergent > pipe, > like a megaphone, and then a convergent pipe, just the opposite, > followed by > a small length of a small dia. straight pipe. The length and diameters > of > each of these sections are somewhat critical but the cones can be > ovaled a > bit and pipes curved usually without too much loss of efficiency. The > unfortunate part of these expansion chambers if they can be quite > noisy. If > you have ever witnessed a 2 stroke racing motorcycle you will know what > I > mean. The factory muffler is likely designed to try and emulate the > characteristics of the expansion chamber in a very small package. Very > hard > to do without some fluid flow type engineers and a dynamometer. Your > best > bet may just be to try and make a unit that is quiet as possible, take > plug > reading and adjust the mixture, and live with any power loss. The > secret to > making a quiet muffler is to rob the sound energy from the exhaust > pulse. > This is done by trying to bounce the sound off as many surfaces as > possible. > Often a "gun" type silencer will do pretty well which is basically a > pipe. > With a bunch of holes drilled in it, surrounded by a chamber stuffed > with > sound deadening material like steel wool or rolled fiberglass. If you > use > this design the deadening material will burn out over time and will > need to > be replenished. A more longer life method may be a series of chambers > with > internal baffles that have holes with the edges deformed like a simple > cheese grater. You may have seen this used in automotive mufflers. By > the > way, have you looked to see if there is a performance aftermarket > exhaust > system for your machine? There may one available that is not too noisy. > Ebay? If you would like to learn more about 2 stroke expansion chambers > and > their theory I just Googled "two stroke cycle expansion chamber design" > and > got a number of interesting hits including some possible chamber design > parameter computer programs. Wikipedia had an excellent animated > discussion > on how expansion chambers work. > > http://en.wikipedia.org/wiki/Expansion_chamber > > > I hope some of this helps out. > > Barry > > > > _______________________________________ > http://www.okiebenz.com > For new and used parts go to www.okiebenz.com > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > > > _______________________________________ > http://www.okiebenz.com > For new and used parts go to www.okiebenz.com > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
