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Old 05-19-2011, 11:39 AM
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Default noise


Question time

I have a pitts wrap arround J-TEC muffler on my YD-A56 and it does not even come close to meeting our field noise requirements at 90 db at 9' , So I am wondering if J-TEC would or could make a long plugs and pipe to go in the exsting pipes that could be drilled with holes ie: kinda like the old glass packs had.

Have tried hi-temp silicon tubing, in various length it work but not enough

Any help is greatly appreciated

Cheers Bob T
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Old 05-19-2011, 12:19 PM
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Kevin Y
 
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Bob,

Yeah, at 9 feet you are most like towards 98db with a standard sized wrap around pitts muffler (also depending on prop). You are going to have a lot of work to do to even get close to 90db at 9 feet and it is going to be a lot more then exhaust.

One of the biggest misconseptions on how to make a muffler quiet is actually doing something like the old glass pack style and drilling holes into the exhaust pipes. You will see some of our competitors do that but it actually doesn't do anything to make it quiet and if you don't do it right you will lose a fair amount of rpm, which yes will make your engine quieter but you probably will not be happy because you can possibly burn up a piston and ring in your engine. When we actually design a muffler we use a formula based on soundwave technology to tackle the problem of noise while working to keep your rpm at the manufactures rpm specs. Thats why on most of our mufflers you will see that we get some of the highest rpm numbers while still being one of the quietest mufflers.

As for adapting anything to your existing muffler the only thing that would really work would be to use the snufflers and remote mount them somewhere inside your airplane. The reason we can not just attach the snufflers directly to your existing muffler is that when we build a muffler for the snufflers we have to build it with supports for the snuffler and a stock wrap around does not have those supports. Even with that you will probably only reach the low 90's range and most people don't really have the room to remote mount the snufflers.

Realistically, you are going need to look at a new muffler and more towards a wrap around pitts muffler that has the snufflers built directly into the muffler or even better one of our large wrap arounds with snufflers built into it. When compared to a standard wrap around the large will knock off about 3db without any powerloss, the biggest downfall is the large will not fit every application because it uses a 2 1/2" diameter can instead of the standard 2" can. Those two options will get you close but you are still going to have to play with props, definitly a 3 blade prop. There are also other contributors to noise, a plane with with a build up wing will generally be a little louder then a plane with a foam sheeted wing. Make sure your covering is tight, any loose covering can contribute to noise. The other thing is carb noise, just as a classic car if you take off the air filter you will get more noise out of your engine. On some of the stuff we have tested we have seen up to 2db just from carb noise.


We are certainly more then willing to work with you and if you can provide us with some more detail about your airframe, prop and overall setup maybe we can help you figure out what will fit your specific application.

Thank you,

Kevin Young
JTEC Radiowave


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Old 05-19-2011, 02:59 PM
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kevin

Thanks for the quick reply

If I was building this bird I Could have planed for snuflers as it was I had to do a lot of hack and wack to get what I have, and did not want to get in to the main fuse structure (see in cluded pic ) I cant go any bigger in Dia on the can, but could go wider by at least 1/2 each side. I do under stand about props and carb noise, I think if I can get rid of the sharp crackle from the exhaust tubes I can get buy. as I mentioned I have tried the silicon tubing and for what ever reason it works and I think it would work better if I could find some that wouls give me a tight fit in the tubes it did coast 50 RPM's and it only reduced the ID to !/2 also on the ground engine only varied about 5 deg's F using a hand held I/R unit with or with out plugs

The bird is a 1/3 Weeks Special so it has a wide front

Cheers Bob T and thanks for your comments
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