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FMF Titanium 4.1 Muffler RTS

Joined Aug 2017
43 Posts | 15+
Australia
I've just removed the stock muffler and fitted a FMF muffler. I now have a whistle when backing off the throttle and I can't seem to get rid of it.

The muffler has a choke ring fitted in the outlet. Take it out and the whistle goes away. I have done a bit of checking and found the muffler has what FMF call RTS which stands for Rapid Tuning System. My thoughts are that changing the size of the choke ring will change the back pressure/shock wave but I can't find any information on it or any interchangeable rings.

Has anyone had anything to do with it and had a whistle which is now starting to annoy me.

Thanks Lance
 
Hey Alan,

There was a slight gap so I sikaflex'ed it in and it made no difference. I rounded the capscrew head and that also made no difference.

Place a finger beside the outlet when revving it and the whistle goes away.

I'm thinking of machining a small grove in the collar near the outlet to see of that stops it
 
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The ring is there to reduce noise level, Ive done some fiddeling with the size in the dyno and 35mm inner diameter is sufficient for a 570, identical output through the range but lower noise by circa 3db, no mapping changes required.

Ive had whistle from the holes left over when NOT using an insert, and its the same phenomena as when you blow on a top of a bottle.
Id take out any sharp edges (unless you already have). Good luck :)
 
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The ring is there to reduce noise level, Ive done some fiddeling with the size in the dyno and 35mm inner diameter is sufficient for a 570, identical output through the range but lower noise by circa 3db, no mapping changes required.

Ive had whistle from the holes left over when NOT using an insert, and its the same phenomena as when you blow on a top of a bottle.
Id take out any sharp edges (unless you already have). Good luck :)

Thanks Tom.....I'll try chamfering the sharp edges
 
Hey Tom, I cut a small chamfer on the outlet of the collar and the whistle is gone...Thanks for your input
Lance
 

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