Mufflers

[Mike G]

Ok guys, here ya go, what have you found that works to quiet noise?

At the moment I have all my boats covered but thought a new topic to help discuss the principals involved would lead to a positive discussion.

I have a Marles pipe, it uses a series of baffles and holes to work, it is a little longer but not any heavier, all SS. I also have a Cooper add on muffler on the stinger of a Mac pipe, quiet but not the quietest. The quietest pipe I have is a Mac pipe with the Cooper WELD on can muffler. Both Cooper mufflers use an offset stinger to quiet them down. The can having a little more volume does the best job. Cooper makes a few different size stingers if that concerns you.

I have inject water into the stinger to quiet pipes in the past, good for 1-2 db at best but it will get you under on race day and can be done at the pond.

My boating partner also uses the internal stinger method, works a treat and actually added a few RPM. I would like to try an internal stinger offset 90* but not willing to drill pipes yet. B)

 

[Tim_Duggan]

There is no substitute for volume! Making the sound change direction before exiting is also a very useful excercise. The thing to avoid is excessive back pressure.

 

[Terry Keeley]

I've been using internal stingers since we adopted a noise rule in '03. Someone mentioned on the RCBoat listbot that he saw something in the Jennings book about it, picked up my copy and read it and couldn't believe it worked as well as he said, so, naturally I had to try it.

My noisiest boat at the time was my 60 hydro running a Picco 67, high comp. head, "Big Belly" CMB pipe, 60% nitro and a rubber mount. I could top 105 dB on a good day, it had what some of my buddies called the "Keeley Cackle". :lol:

The stinger alone brought it to 91-92 and if I put my Muck double cone muffler on it also it goes to 89-90. I ran this combination at this years Nats with a CMB (no after muffler) and was not given a warning, and they had plenty of time to check it as I ran open water a lot both Friday and Saturday.

A trick I found was that if you make a drain hole in the stinger keep it 1/16" or smaller, any openings bigger than that near the end of the pipe (high pressure area) increases the noise dramatically.

Workin' for me and I can use all my old pipes!

 

[Chris Wood]

Terry,

What size tubing are you using on the pipe. and how far in does it go...

I am assuming you have to expand the pipe stinger??

Thanks,

Chris

 

[Terry Keeley]

Terry,

What size tubing are you using on the pipe. and how far in does it go...

I am assuming you have to expand the pipe stinger??

Thanks,

Chris

I use 1/2" tubing with 0.035" wall so that's 0.430 I/D. I turn it down most of the length to about 0.460" and leave 3/4" on the end full diameter to act as a lip to keep it from falling back inside the pipe. You could also use 15/32" brass tubing (7/16" I/D) and solder a short piece of 1/2" to the end. Red Locktite holds it well.

Yes, the CMB needs the stinger stretched, I use gauge pins going bigger and bigger 'till I get to the right size, but you could use something else if you look around. Most pipes need the stingers choked anyway, so this works well. You need the tube to go to the start of the converging cone or the weld on most pipes.

 

[Chris Wood]

thanks

chris