cappaj1

My Feedback: (1)

Someone at the field today said I should use flexible exhaust line from a company like MACS in order to use the stock muffler and route it the way I need to inside the cowl of a biplane.
Anyone have experience with this? How does it attach to the engine and to the exhaust itself, both which are threaded on my OS Max FS-120 four stroke.
http://www3.towerhobbies.com/cgi-bin...4&I=LXZ671&P=K
Thanks in advance.

Rodney

4 Stroke exhausts are much hotter than 2 stroke and many exhaust extensions will not hold up to the high temps. Be sure to check on whether or not this will stand up under a 4 stroke exhaust temperature before you buy it.

ChuckW

The Macs web site shows a little more detail:

http://www.macspro.com/four_pre.asp#thread_index

I'd give them a call and tell them your application. I bet they can set you up with exactly what you need.

OS also sells a short and long flex pipe for that engine:

http://www3.towerhobbies.com/cgi-bin...?&P=8&I=LXCB20

http://www3.towerhobbies.com/cgi-bin...?&P=8&I=LXCB21

Have you thought about a pitts muffler?

http://www3.towerhobbies.com/cgi-bin...?&I=LXFH01&P=7

There are also adapters to help you angle the stock muffler just right:

http://www3.towerhobbies.com/cgi-bin...?&P=8&I=LXCA97

http://www3.towerhobbies.com/cgi-bin...?&P=8&I=LXCA98

cappaj1

My Feedback: (1)

ChuckW,

Thanks for the info and especially the links!

As for the pitts mufflers, my club seems to be frowning on them due to noise issues, valid or not, lately so I wan't to stay away from them. I realize the stock muffler really doesn't muffle much -after taking a look at the inside of it, doesn't seem like it's really muffling much at all

Gray Beard

My Feedback: (-1)

Jim, I have run my OS 1.20s with no muffler at all, just the flex pipe and no one knew I didn't have A muffler on them. One I had inside A big round cowl with A rubber fitting sticking out the bottom of the cowl to direct the engine snot, it sounded so cool!! Everyone with A bipe wanted one of those cool sounding mufflers. A four stroke just isn't A loud engine at all. That's one of the beauties of them.

cappaj1

My Feedback: (1)

What did you use for a pressure line?

Also, what is the outlet on the bottom of the crank for, the one I have the arrow pointing to, do you know?

I have three outlets that look like they are for fuel tube, the fuel inlet by the high speed needle, the pressure one on the muffler, and this third one.

2slow2matter

My Feedback: (1)

That third nipple is for crankcase pressure to be vented out. Attach a fuel line to it and direct it down and out of the way. it will dispell a lot of oil too, so point it somewhere you don't want all that mess on.
It cannot be used to pressurize the tank, however.

If you put the tank just right, you won't need any tank pressure.

Gray Beard

My Feedback: (-1)

I have two of the OS 1.20s and both are pumped so I needed no pressure line, as A mater of fact pumpers are just the oposite, they have an open vent line on the tank. Think about it like this, take A two line fuel tank, plug one end and suck on the other line, doesn't take too much to empty the air out of it, A pumper sucks the fuel out or draws it. You can get the pressure nipples from places like Tower when you are buying the flex pipe, you just drill and tap the top part of the flex line just on the outside of the header part and install the fitting, not real hard. A lot of mufflers like the slimlines come without a pressure fitting and you have to do that too.
I just brought up the flex line only to show you that a four stroke is not A loud engine and no one would know if you had A pitts type muffler or not. There are some great in cowl mufflers, take A look at Central Hobbies, they have A lot of four stroke stuff. With the flex pipe you are supposed to hook up the stock muffler at the other end anyway. With A four stroke there are A lot of ways to do things.
Gene

bigtim

My Feedback: (13)

here's a heads up about any of the flex pipe/headers OS has available on the Towerhobbies site there fitted for the newer OS engines and may not fit your older OS120.

I have a med.aged OS 120 pumped engine,about the same age as yours, that I wanted a close muffler header to keep the pipe inside the cowl, and when I tried one that my LHS ordered for me, the threads and pipe size were different, for the newer 120 4st engines the pipe diamiter is smaller,and the threads are alot finer.

if you order a pipe make sure you call tower and let them know wich model engine your buying it for, you might be stuck using the stock pipe because of availability.

my 120 pumped and pipe out the side of the cowl when its in the air theres not much to see

da Rock

Slimline is just now releasing a new line of their Pitts mufflers that they have labeled "Quiet Zone" because they're supposed to be significantly quieter. I've got one that's due from Tower today and will get checked out very soon.

They are for 2cycles, btw.