Muffler insulation

[Jon 2]

On my Avid Mark IV I finally have the muffler hung.  It appears close to everything radiator lines (radiator on belly), firewall and cowling (I think I have the 1/2 inch clearance all around). I was at a gathering of Sonex planes and they had the exhaust fully covered with insulation wrap.  My manual said nothing about a wrap but do any of you have a wrap on your exhaust?  If you do, does it affect the integraty if the exhaust metal by holding in the heat?  It may not if the Sonex guys do it.  Also, did you use the high temp silicon on the muffler springs?

 

 

 

Thanks for all

 

Jon

[EDMO 1078]

Jon,

     I am only repeating what an "exhaust expert" wrote in Sport Aviation or Kitplanes mags - He stated that "If you wrap your exhaust, it will fail".  I cant verify this, but it sounds logical, since part of the job of the exhaust is to get rid of combustion heat.

     I think you would be better served to make and install some sort of heat shield to go between the muffler and other stuff, if that is possible, or to try to move something.

EDMO

[RDavidson 183]

I've researched this on another project and I've talked to Jon about it.

Ed, you are right in that people say it will cause your pipes to break down faster than normal, but there are a couple of things to think about...

How much faster? Well, all I know is that Car guys aren't constantly burning through headers, but they are also not full throttle all the time.

Stainless Steel exhaust vs normal car exhaust steel? We use stainless in aircraft for the extra durability. So wouldn't it breakdown slower?

I don't have any exact information for those questions, but if you are having trouble finding room in your cowling and are risking melting your cowling or vapor lock issues, why not wrap your exhaust? So what if you will have to change the exhaust sooner, it is better than melting a cowling or flaming out...right?

I think the argument will be that if you rig it right you don't need the wrap.

Can anyone tell Jon what the proper clearance should be or give him pics of your exhaust setup?

Thanks,

Ron

[EDMO 1078]

I agree with what you said Ron - I just suggested a heat shield as an alternative - some have put the aluminum heat shields inside the fiberglass cowling to protect it too.

If this was a 4-cycle, I would mention burned exhaust valves with wrapped headers...

EDMO

[Jon 2]

Good information.  I have the 1/2 inch clearance as required but you know me I like to over engineer.  The two water pipes (belly radiator)  on each side of the firewall that are close to the exhaust I plan to wrap them rather than the exhaust pipes.

 

On the muffler I can put part of an insulation blanket on the front and back to protect the fiberglass and firewall.  This should work.

 

Thanks again for the information.

 

Jon

[Av8r_Sed 82]

Jon,

I had my 582 exhaust ceramic coated.  It ends up with a silvery metallic finish.  Though I don't have before/ after data, it does seem to move more heat out of the cowling.  It makes sense since nothing radiates heat better than a flat black surface (in this case inside the cowling).

[Guest]

Everyone I know is wrapping the pipes on their 912's without problem. Most are not wrapping the mugffler, but installing a heat muff to extract heat for the cabin. Wrapping the pipes and installing a muff on the muffler keeps oil and cooling hoses as well as engine mounts from being destroyed by heat.

[Guest]

I plan to wrap my 912 exhaust pipes and wrap the muffler with a cabin heat muff. That said, The exhaust in my Magnumm was not wrapped and I saw no reason to do so. Clearances were adequate. Similar with my 582 MK IV. Never wrapped, but clearances were not an issue there either.

So...exactly how is wrapping supposed to shorten the life of the exhaust?

Chris

[Dusty 126]

Wrapping headers on auto use appears to make them brittle

The last thing Anyone needs is a cracked exhaust under a wrap that may get missed at preflight

A heat shield would be the best option if needed.

There is a lot of air going through a cowling!

[RDavidson 183]

Chris, from what I read about it, wrapping them makes the metal reach higher temps because it can't radiate the heat into the normal airflow. So the higher temps cause it to break down more quickly. I would like to see some real data on that though.

Dusty, your point is the best one against the wraps that I have heard. I would think that you might want to replace the wrap at each conditional inspection or have a carbon monoxide sensor inside the cockpit as a backup? I don't know...

Is a muffler necessary? Is it too loud without it? I don't know much about Rotax motors...you usually run straights on Lycoming engines.

[EDMO 1078]

Ron,

     The article I read about a guy who has built exhausts for some (30?) years, said that the heat buildup destroys the metal faster, (destroys chrome and causes rusting?), and because the wrapped exhausts are not as good at getting rid of heat, a 4-cycle can end up with burnt exhaust valves.

     From what I understand, the 2-cycle has to have a specially-built exhaust system that works to get the exhaust air out to make room for air to be sucked in - like a plenum chamber changes velocity of air - something like that - without the proper exhaust, the 2-cycle wont run right at different speeds - guess the special muffler is part of that system - think this is a problem they are having with the 670 in a plane because of designing an exhaust that fits in the cowl?

    Someone else might explain this better than an old 4-stroker can.  We only use mufflers to make our engines quieter, but they can prevent shock cooling / warpage to exhaust valves after shutdown, and they are an additional heat sink, so I have heard...

My Soob came with 12" straight exhausts, but plan on adding two 12" chrome glasspaks if possible.  I don't think I can use the Stratus exhaust and muffler because of my nosegear, but they claim it adds 10 hp   I don't see how!

     In some European countries, a plane has to be about as quiet as you can make one - I forget what decibel level - Guess everyone has heard about the 5 foot long "Swiss" homemade mufflers....There are articles on how to make them.

I think a couple of our members have them...

EDMO

Edited 11 Jun 2015 by Ed In Missouri

[RDavidson 183]

Thanks Ed...I didn't even think about burning valves! Makes sense...

[EDMO 1078]

Ron,

     Not only burned exhaust valves, but your EGT gauges might read higher with wraps.

     I don't plan on EGT for my Soob - the car didn't have them, and my carb is non-leaning. 

     I don't fly higher than about 3 or 4000 msl, our highest "Mountain" is 1700 msl,

so don't think I need them unless the prop pitch changes EGT too much, and mine is not IFA.

     Just fly fat, dumb and happy as long as there is gas in the tank and the fan keeps turning! 

     Anyone care to comment on this?  Maybe NOT about fat, dumb and happy!

EDMO

Edited 13 Jun 2015 by Ed In Missouri

[ljboyers 0]

Hello,

 

New here but responding to the muffler question.  900 hrs on the muffler in the attached photo without any problems.  The heat muff provides plenty of heat and defrost for temps to 10 degrees.  

 

The Stratus mufflers were supposed to add hp by having opposing pulses providing added scavenging.  I had two straight pipes before the muffler and believe I did gain a little by adding the muffler.  

 

Keep in mind that added items not needed affect performance.

 

Regards,

 

L Boyer

[EDMO 1078]

Is that a Stratus engine?  I was just asking Reiner Hoffman about what kind of starter Stratus used, and didn't get an answer.

I have a Dave Johnson EA-81 with stock geared Soob starter (heavy) and Holly 5200 carb and straight pipes but plan on 2 glaspaks because I have nosegear.

EDMO

Edited 14 Jun 2015 by Ed In Missouri

[ljboyers 0]

Yes it is a Stratus.  One of the earlier ones that Reiner put out.  I am currently in Anchorage AK but will be back in Ketchikan AK later in the week for a day or two and could see if there is any information on the Starter you could use.  I may have a set of straight exhaust pipes but would suggest trying noise canceling headsets before adding the weight of glaspaks.

[EDMO 1078]

I think that either Suberavid or my engine book said you could use a lightweight starter from a Chrysler or Dodge (Colt or something), or some foreign car, but Reiner talked like a geared starter was needed - Yours looks heavy too - Got to check back with Randy on this too.

12" motorcycle glaspaks shouldn't be too heavy, and help protect valves...

I hate wearing earplugs and earphones!

Thanks,  EDMO

Edited 15 Jun 2015 by Ed In Missouri