Zeroman

I ran my Rossi 40 for the first time today, it is in a Doddger Q 500.The problem is it is far to loud, way over our limit of 96 db.Any suggestions on making it meet the 96 mark.Thanks for your input.Chris.

Kaos1

Zeroman,

What prop are you running? I used a Hatori quite pipe on mine and propped/tuned it for around 12K and it was pretty quite.

Kaos1

Zeroman

Im breaking it in with a 9x6 APC @ 16,400 and would like to fly it with a 9x8.Chris.

Rudeboy

You want speed...? It's going to make noise... no way around it...

Why do you have to stay below those 96 db'S? Club rules? Racing rules?

Which muffler do you have on it now?
You can prop it down, but it is going to cost power in a big way...

Other "powerful" mufflers are going to make just as much (or more) noise... and since you are racing (well, I suppose so) you cannot use pipes or anything...

What are the other guys using for power? If they can stay below the noise limit, and make decent power... follow their lead...

Razor-RCU

My Feedback: (50)

I had a similar problem with my Rossi-45, it was somewhere near 104db's .... No I never quieted it down- My Jett-50 made more power and was noisy but the Rossi has such a throaty sound that the old club-members noticed... They did not mind the Jett-

Rudeboy hit it on the head- Speed requires copius amounts of noise (in most cases-)

The other gentleman that set his tuned pipe at 12K must not be shooting for speed--- Pattern maybe?

happyal

Hi Bud,

I've got my Rossi 40 running on a Tuned pipe, turning a 8 * 8 prop and it is very loud.

Club members also noticed this sound but luckly noone seems to mind too much about it.

bob27s

My Feedback: (19)

At anything much over 16K rpm, its gonna be loud. The prop noise is a monster even from a 9 " prop.

What exhaust are you running on it now ?? What did it measure at when you were checked for sound level (I assumed they checked it if you have a sound limit rule). If you are running the older rossi stock mini-pipe/muffler, those were notoriously loud.

Initially, might I suggest....
Loading the engine up with a 9x8 or 9x9 - get it down around 15K or less peak RPM on the ground.
Install one of the Jett-Stream mufflers - specifically the one designed for the SJ-60L. This is tuned for 14 to 17K. There is an adapter available for the rossi installation - simple bolt on configuration. The prop will unload in the air, bringing the engine up into the sweet spot for the muffler. I can't guarantee 96 db, but this will be quieter than what you have now.

Resulting combination will be very quick...... might even surprise you The muffler has a fairly broad range, so if you want to drop to a smaller blade/pitch or go with a pylon prop (more RPM) the muffler will help the engine turn up even higher.

The port timing on the Rossi is fairly high, and dragging it down much lower than 14K peak will require a full size pipe set fairly long. Would be hard to install the configuration on a q-500 type plane ( I have tried... its not pretty)

Getting to 96db will be tough unless you drop the rpm and/or get a much more effective muffler.

For reference, my SJ-46 with a turbo-jett muffler..... 12x4 APC..... 14,000 rpm... installed within the cowl of my P-51 ... measured at 94 dB two weeks ago (3 meters, on grass, highest reading).

Zeroman

Rudeboy, the 96 db cap is a club rule.Im not racing this plane, but my plan was to use it for our Need for Speed event, in which case i could run it for that day the way it is.Im all to familiar with noise and tune pipes, i raced RC boats for 15 years.This is a picture of the Rossi,you can almost put your pinky in the end of the muffler, if you can call it that LoL.I bought this engine off a guy that use to race, so its a few years old.Im wandering if there has been design changes on the pipe or is this what Rossi still uses.It truely has a very aggressive engine noise, more so than the prop.Are there any after market mufflers that you could recommend that could reduce the sound about 3db and still give me good power.I had a Nelson 40 with more power than this engine and it was nearly not as loud.Chris.

Bob.R

My Feedback: (2)

Get a jett stream muffler from Dub Jett as suggested by bob27s. It will cut the noise and deliver performance.

RossiRay

The current Rossi "muffler" (that's Italian for megaphone) mounts differently but is the same operationally. It is truly brutal on the ears!

Get a Jett Stream or Nelson Ultrathrust and enjoy the same power and less noise.

RR

Zeroman

Thanks for the info guys.Will give Dub a call.Chris.

jaka

Hi!
Why not get the quiet Rossi pipe..it looks the same as your old Rossi "silencer" but is much more quiet.
Rossi .40 engines have been delivered with these quiet silencers for for over two decades now.
The silencer you show was one that they had 25 years ago and it sure is LOUD!

Regards!
Jan K
Sweden