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Hi exhaust temp and mufflers


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Anybody tried an Akrapovic EVOLUTION SLIP-ON partial exhaust system built for Yamaha motors. When tested the temperature of the header tubes exceeded 800ºC and it held up.

 

I know that the exhaust heat from a rotary engine can destroy most mufflers... so I just wanted to know if poeple that fly these installation have though of using a motorcycle exhaust... as they are light and built, as far as racing exhaust are concern, to handle hi exhaust temps...

 

Maybe they can survive to the abuse of a rotary... and maybe not...

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I know the european bike community like this brand alot - a set for a KTM 950 is upwards of a grand. Ralley bikes use them in competition.

 

Can't see the packing lasting very long if you blow flame thru it though. Can't see that Roadstar lasting very long either...with those red pipes right next to the engine case.

 

Maybe something like a Borla stainless header muffler or a stainless Flowmaster (which is chambered and has no packing) would work. If you can make it fit.

Marc Oppelt

Olympia, WA

http://picasaweb.google.com/oh.u8it2

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Anybody tried an Akrapovic EVOLUTION SLIP-ON partial exhaust system built for Yamaha motors. When tested the temperature of the header tubes exceeded 800ºC and it held up.

 

I know that the exhaust heat from a rotary engine can destroy most mufflers... so I just wanted to know if poeple that fly these installation have though of using a motorcycle exhaust... as they are light and built, as far as racing exhaust are concern, to handle hi exhaust temps...

 

Maybe they can survive to the abuse of a rotary... and maybe not...

ever heard of photoshop. its called advertizing. if they are using a material thats gets that red on the entire pipe they are doing something wrong. it never happens like that. even a F1 engine exhaust does not glow that red unless seen in a dark room. 800c is 1475 degrees F and thats not that hot. again advertizing hipe. the reason they make these claims is that most of the industry uses Type 304 stainless and it will work but not hold up to the same temps. They may be using Type 321. The lycoming will run up to 1550F with out a problem. the aircraft exhaust should be made out of type 321 stainless. it will take 1800 F no problem. the rotary seems to get hotter because there are more power pulses coming out of fewer pipes so the pipe does not get a chance to cool between the pulses. so the pipe runs a bit hotter. should not be a problem for the 321 stainless but if you want a material that can stand up to higher temps you can use 625 Inconel but you may want to be seated when you hear the price. at $235 per foot for 1.75" tubing. 90 degree bends are only $425 each you may want to rethink your choice. that and the labor can make an F1 exhaust system cost as much as a lycoming engine. as far as mufflers go, most do not use them, they are heavy, take up space we don't have, have parts or packing that may come out and hit the prop and we really don't need them. Aircraft engines can seem loud when you stand next to them on the ramp but remember most of the noise is from the prop. on an EZ we have a natural muffler, the prop, it does help break up the exhaust noise. The loudest aircraft are the ones with the CS prop in low pitch for take off.

Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years

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You need to check with the FlyRotary.com group for Mazda specific questions. Iconel or Stainless seems to be the favorite approach as well as 'custom' for your application.

 

We do not push the HP such that you get into the super-heated range but here is a link to a

putting out 1600+ hp.

 

At least I don't think it was photoshopped.

T Mann - Loooong-EZ/20B Infinity R/G Chpts 18

Velocity/RG N951TM

Mann's Airplane Factory

We add rocket's to everything!

4, 5, 6, 7, 8. 9, 10, 14, 19, 20 Done

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Anybody tried an Akrapovic EVOLUTION SLIP-ON partial exhaust system built for Yamaha motors. When tested the temperature of the header tubes exceeded 800ºC and it held up.

 

I know that the exhaust heat from a rotary engine can destroy most mufflers... so I just wanted to know if poeple that fly these installation have though of using a motorcycle exhaust... as they are light and built, as far as racing exhaust are concern, to handle hi exhaust temps...

 

Maybe they can survive to the abuse of a rotary... and maybe not...

I think that there are two issues with the rotary exhaust.

 

The first, of course is the higher heat, however the second issue, and perhaps more important on the issue of the physical security of the system is the nature of the exhaust pulses. In a standard engine, the exhaust pulses are attenuated by and cooled, somewhat, by their path around the exhaust valve and associated caverns on their way to the exhaust tubing. With the rotary, each pulse exits, unattenuated into the piping.

 

Since the Renesis exhaust goes through a different path (through the side housings) the exhaust path is more similar to an engine of the valvular persuasion. They are, from what I understand, quieter.

I Canardly contain myself!

Rich :D

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Yeah ..... pretty much everything Rich said.

Not only are you dealing with exhaust that is hot but it is supersonic as well. Most mufflers will not stand up to that combination. In time it will blow the guts out of them.

 

There are a ton of RV guys flying the rotary that have been working this issue on the fly rotary group and they seem to uncover a lot of options. Most of the development of the rotary centers around the RV application simply because it's the most popular project being built.

 

If Tracy Crook or Ed Anderson haven't done it already (no matter what the rotary question is) I would be surprised.

T Mann - Loooong-EZ/20B Infinity R/G Chpts 18

Velocity/RG N951TM

Mann's Airplane Factory

We add rocket's to everything!

4, 5, 6, 7, 8. 9, 10, 14, 19, 20 Done

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Yeah ..... pretty much everything Rich said.

Not only are you dealing with exhaust that is hot but it is supersonic as well. Most mufflers will not stand up to that combination. In time it will blow the guts out of them.

 

There are a ton of RV guys flying the rotary that have been working this issue on the fly rotary group and they seem to uncover a lot of options. Most of the development of the rotary centers around the RV application simply because it's the most popular project being built.

 

If Tracy Crook or Ed Anderson haven't done it already (no matter what the rotary question is) I would be surprised.

I think that Tracy has solved the temperature problem with an exhaust coating that is put on the inside and outside of the pipes. I heard, that after running the engine, you can actually touch the exhaust pipe and not get burned. I think that others have seen this at the rotary fly-in at tracy's place. I only know about it second hand.

 

The muffler is another story. After disgarding the turbo, Buly found that the turbo housing, for the rotary did a good job of muffling. Then he got rid of the rotary.

 

I think, but do not know for sure that the renesis has solved both of these problems, or has minimized them. Time will tell

I Canardly contain myself!

Rich :D

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I'm going to cross post this from the Fly Rotary list.

It pretty much tells the story as to the level of understanding that is offered on the subject of rotary engines:

The beast in the rotary is a supersonic shock wave that is traveling in a very fast moving superheated media. Say 1600 degrees. So there is energy that is a compressed portion of the gas (the sound), energy in the form of a high temperature gas and the energy represented by the velocity of the gas.

 

So, you can take out energy by cooling the gas, by slowing the gas. And the sound may be removed by reflection, as in the noise cancelling headsets. Or, by homogenizing more uniformly throughout the gas.

 

To impinge on the flow is to make it change direction, and, or, velocity, like the poor header system design or the square header/muffler idea. Where drag or just design helps homogenize the sound waves and spreads them time wise. So a muffler that dies quickly when mounted close to the engine, may last much longer when mounted at some distance from the engine.

 

The high pressure of each pulse spreads in both directions in the gas and its peak pressure is reduced. The only energy lost would be the heat radiated by the longer tube exposed to cooling air. But the peaks are reduced as a function of time, so stress seen by the muffler parts is reduced. Suppose the pipe were 100 feet long. The pulses would be nearly 100% homogenize, and most of the heat energy would have been radiated by the pipe. The sound energy left over could be easy to deal with.

 

To change flow direction close to the muffler like the Inconel splitters in the NA rotor housings requires exotic materials. The splitter slows a part of the shock wave and accelerates the rest of it, but spreads it so its peak pressure is reduced, and a less complex muffler can be effective. The splitter impinges on the flow.

 

Even the stainless Mazda racing muffler did not last long when mounted close to the engine. It has a room at the front where the shock wave can expand and slow to subsonic. Half of the battle is won.

 

Some muffler designs use part of the pulse energy to impinge on the main flow through the muffler. The glass pack or steel pack muffler (a Swiss muffler with packing) allows high pressure to bleed into the larger volume of the packing chamber near the front, and further along the muffler gasses at lower energy (after heating the media) are flowing out of the media to impinge on the flow exiting the central tube of the muffler. (like a big electrical capacitor) A relatively effective system so long as the packing remains in place. Once the packing is gone, the muffler may start to favor some frequencies over others and muffling effect will drop to near zero.

 

Conventional car mufflers are very advanced. They must outlast the warranty period (just barely) and meet some strict sound profiles. They use cooling, impingement, reflection and cavity resonance, to remove particular frequencies. They may be tailored to particular engines. Unfortunately they are also very large, heavy and hot. The tubes of various lengths inside the muffler cavities absorb offensivee notes peculiar to some Engines/systems. A rotary may sound great at speed while a Chevy odd fire V-6 may sound like

s---t. Never quite right.

 

Reflective mufflers break the pulse into two or more parts and then direct the two parts into a head-on collision. This scheme may be used more than once in the same muffler. The energy expended in each of these events must be removed as heat, and in some cases as movement of the sides of the (soon to fail) muffler.

 

 

 

T Mann - Loooong-EZ/20B Infinity R/G Chpts 18

Velocity/RG N951TM

Mann's Airplane Factory

We add rocket's to everything!

4, 5, 6, 7, 8. 9, 10, 14, 19, 20 Done

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Tracy tested the Spintech and it worked very well. At the time most of the people flying were RVs and they were looking for a muffler that was streamlined so they did not prefer the Spintech as it is a box. It can be built with 321 stainless. I was going to order a steel unit to see how it would play with the augmentor then get one built in SS. It is inside the cowl so aerodynamics is not required.

 

Joe Berki

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