Mailing List Message #65318
From: William Jepson <>
Subject: Re: [FlyRotary] Exhaust setups
Date: Sun, 10 Nov 2019 20:42:12 -0800
To: Rotary motors in aircraft <>
Matt, and others,
Powersport had good luck with a flowmaster medium square can muffler, but they cut it open and replaced the baffles with inconel to handle the heat. The suggestion was to use a muffler that has at lease 2X the swept volume of the engine in the primary chamber.. This does help with the noise and lasted pretty well. Be sure your welder is good. This muffler helps in two ways it lowers the tone and lessens the volume. As an arunning  Mlternate look up the Iannetti Patent. He made mufflers for the IMSA guys and they worked great. In fact at first he would only lease the muffler to the various teams running Mazdas.

On Sun, Nov 10, 2019 at 7:38 PM Matt Boiteau <> wrote:
What are you guys running for exhaust? The thing is stupid loud and can barely talk on radio. Headset is LightSpeed wireless Tango's. Their ANR does not work well with the pitch of the rotary. Will try a Bose headset tomorrow.

I have 2.5" exhaust leaving the cowl. (ex1.jpg)  It comes down and centers the bottom of the plane into a 4" outer pipe. (ex2.jpg) The 4" outer pipe (5ft long) is open to the free air and exits behind the rear bulkhead. The 2.5" converts to a 3ft long perforated pipe (ex3.jpg) and exits inside the 4" outer pipe. For fun, I filled it full of ceramic fiber insulation mat, which did help a little until it blew all out.

- Matt Boiteau
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