Mufflers

[SkySteve]

I want to quiet my Rotax 912A (80 hp). My exhaust system has been modified as there is no room inside the cowl for a Rotax muffler. Each side of my exhaust is connected so I have 2 header pipes exiting the bottom rear of the cowl next to each other just left of center [pilot side], one header from each side of the engine. I've tried a pair of custom mufflers and am not happy with the results (still way too loud) and I would like to go to a single muffler.

Any advise for "under the belly" type muffler solutions would be appreciated.

[Dick B in KY]

Steve, This won't get you to a single muffler, but, have you thought about removing the collectors and installing individual motorcycle internal mufflers in each exhaust pipe? Just need to have each exhaust pipe the same length for best scavenging.

Dick B

[SkySteve]

Dave,
No. I haven't thought about motorcycle mufflers. I did replace the ones in the photo with 2 VW mufflers. They are small and about the same diameter as the header pipes, but still WAY LOUD.

I've heard of a Swiss muffler that is suppose to be very quiet, but really know nothing about it other than I think it is between 3-4 ft long. Does anyone know anything about this?

[Av8r3400]

The "Just" guys have been using Motorcycle "SuperTrapp" slip on mufflers with some success. They are tunable for back-pressure and noise.

My friend just completed a plane using a 912UL motor and he built his own muffler. It is possible. The internal volume is available from Rotax and you just build the size and shape that fits your needs. He used a wrecked Rans muffler for the blast tube (inner tube with holes in it) and built his own case.

[t j]

Here's a link to the history and how to of the Swiss muffler. They build them theirselves.

http://www.piteraq.dk/flight/muffler.html

[SkySteve]

Thanks Av8r3400 and tj. Some good input and reading. I'll check out the Rotax specs and do some additional research. Thanks for the ideas.